Engineering flOUTOSSI 3 Jfl UNIVERSITY OF CALIFORNIA * KTLvIEKT O!T CIVIL THE BUILDING LAW OF THE CITY OF BOSTON. BEING ACTS OF J907, CHAPTER 550. Published by THE MASTER BUILDERS ASSOCIATION, No. 166 Devonshire Street, BOSTON, October, 1907. CONTENTS. PAGE SECTIONS 1-10. BUILDING DEPARTMENT. Organization, Officers, Powers, etc. . . . 1 SECTION 11. BUILDING TERMS. Definitions of Words Used 7 SECTIONS 12-13. BUILDINGS, REQUIREMENTS FOR ALL. Permits, Prohibitions, etc. 7 SECTIONS 14-16. BUILDING MATERIALS. Brick, Iron, Steel, Concrete, Wood, etc 10 SECTION 17. BUILDING CLASSIFICATIONS. First, Second, Third, Composite . . . 16 SECTIONS 18-41. BUILDING CONSTRUCTION. Height, Excavations, Piling, etc. . , . . .... . 18 SECTIONS 42-76. TENEMENT HOUSES, ADDITIONAL REQUIREMENTS FOR. Definitions of Terms, Fire-escapes, etc. . . > . . . . . . 29 SECTIONS 77-111. THEATRES AND PLACES OF PUBLIC ASSEMBLY. Construction, Courts, Curtains > etc 41 SECTIONS 112-124. PLUMBING AND PLUMBERS. Definition of Terms, Registration, Inspection, etc. ..... 49 SECTION 125. HAZARDOUS BUILDINGS AND APPLIANCES Regulations Relative to . . ' . .' ... . . ... 57 SECTION 126. COMBUSTIBLE MATERIALS. Habitable Buildings Not to be Used for Storage, etc . . . . . 58 SECTIONS 127, 129. ENFORCEMENT OF ACT. Jurisdiction in Equity and at Law . . . . .' . . . . 58 SECTION 128. BOARD OF HEALTH, POWERS OF. Relating to Occupants, Light, Ventilation, etc. . . . . . . 58 SECTION 132. NUISANCE. When a Building becomes a Nuisance. . . . . . . ; . 59 SECTION 133. REPEALS. Acts 1892, Chapter 419 59 SECTION 134. THIS ACT TAKES EFFECT August 1, 1907 ...... 59 CIVIL ENGINEERING 0. of C. THE BUILDIN LIBRARY OF THE CITY OF BOSTON. ACTS, J907 CHAP* 550. AN ACT RELATIVE TO THE CONSTRUCTION, ALTERATION AND MAINTENANCE OF BUILDINGS IN THE CITY OF BOSTON. Be it enacted, etc., as follows: SECTION 1. There shall be in the city of Boston a department to be called the building department, which shall be under the charge of the building commissioner. The commissioner, who shall have had at least five years' experience as an architect, a builder, or a civil engineer, shall be appointed by the mayor, for a term of five years. He shall receive such salary as shall be fixed by the city council, with the approval of the mayor. The present officers and employees of the building department, except the board of appeal, shall hold their several offices and positions until removed or discharged according to law. The commissioner may, with the approval of the mayor, appoint such number of inspectors, employees, and assistants as the city council shall, from time to time, determine. No person shall be appointed as inspector of construction who has not had at least five years' experience- as a builder, civil engineer, or architect, or as a superintendent or foreman or a competent mechanic in charge of construction. The commissioner may appoint as his deputy an inspector in the de- partment who shall, during the absence or disability of the commissioner, exercise all the powers of the commissioner. No officer connected with the department shall engage in any other business or be interested in the doing of work or the furnishing of material for the construction, repair or maintenance of any building, or in the making of plans or of specifi- cations therefor, unless he is the owner of the building or a member of the board of appeal. The clerk of the department shall, under the direction of the commis- sioner, keep a record of the business of the department, and the commis- sioner shall submit to the mayor a yearly report of such business. The records of the department shall be open to public inspection. The com- 800296 . - :- - : /. .->/-! V .* * Jl *** * * 4 * Acts of 1907, Chapter 550. missioner may require plans and specifications of any proposed structure or for the alteration of any structure or building to be filed with him, duplicates of which, when approved by the commissioner, shall be kept at the building during the progress of the work. Such duplicates shall be open to the inspection of any inspector in said department. The commissioner shall grant permits for the construction, alteration, removal or tearing down of buildings or structures, and for plumbing, gas fitting, and the setting and maintenance of steam boilers and furnaces when applications for the same are made and filed in conformity with law. All permits issued by the commissioner shall be on printed forms approved by him. If the commissioner finds that the terms of a permit are being violated, he may, after notice mailed to the person to whom the permit was issued, order the whole or any part of the work, which is being done under the permit, to be stopped, and such work shall not be resumed until the terms of the permit have been complied with. All applications for permits under the provisions of this act shall be in writing, on forms furnished by the department. The commissioner may require the material facts set forth in the same to be verified by the oath of the applicant; he may also require, in his discretion, a survey of a lot on which any proposed building is to be erected to be filed with the application. Every application shall state the name and address of the owner. SECT. 2. The commissioner, or one of his inspectors, shall examine as often as is practicable every building in the course of construction or alteration, and shall make a record of all violations of this act and of all other matters relative thereto. The publication of such records with the consent of the commissioner shall be privileged. SECT. 3. The commissioner, or one of his inspectors, shall examine any building reported as dangerous or damaged, and shall make a record of such examination, stating the nature and estimated amount of the damage, and the purpose for which the building was used, and in case of fire the probable origin thereof; and shall examine all buildings in respect to which applications have been made for permits to raise, en- large, alter, or repair, and shall make a record of every such examination. SECT. 4. The commissioner, or ore of his inspectors, shall inspect every building or other structure or anything attached to or connected therewith which he has reason to believe is unsafe or dangerous to life, limb, or adjoining buildings, and if he finds it unsafe or dangerous, he shall forthwith in writing notify the owner, agent, or any person having an interest therein, to secure the same, and shall affix in a conspicuous place upon its external walls a notice of its dangerous condition. The notice shall not be removed or defaced without his consent. The commissioner may with the written approval of the mayor order any building which in his opinion is unsafe to be vacated forthwith. SECT. 5. The person notified as provided in the preceding section shall secure or remove said building, structure, attachment or connection forthwith. If the public safety so requires, the commissioner, with the approval of the mayor, may at once enter the building or other structure, the land on which it stands or the abutting land or buildings, with such assistance as he may require, and secure the same, and may erect such Acts of 1907, Chapter 550. 5 protection for the public by proper fence or otherwise as may be neces- sary, and for this purpose may close a public highway. SECT. 6. There shall be in said department a board to be called the board of appeal. Said board shall consist of five members appointed by the mayor in the following manner: One member from two candidates, one to be nominated by the Real Estate Exchange and Auction Board and one by the Massachusetts Real Estate Exchange; one member from two candidates, one to be nominated by the Boston Society of Architects and one by the Boston Society of Civil Engineers; one member from two candidates, one to be nominated by the Master Builders Association and one by the Contractors and Builders Association; one member from two candidates to be nominated by the Building Trades Council of the Boston Central Labor Union; and one member selected by. the mayor. These appointments shall be subject to confirmation by the board of aldermen. The appointments first made shall be for the terms of one, two, three, four, and five years, respectively, so that the term of one member shall expire each year. All subsequent appointments shall be for the term of five years. Vacancies shall be filled in the same manner in which original appointments are made. Each member of said board shall be paid ten dollars per day for actual service but not more than one thousand dollars in any one year. No member shall act in any case in which he is interested, and in case any member is so disqualified, the remaining members shall designate a substitute. - r All the members of said board shall be residents of or engaged in busi- ness in Boston. Every decision of the board shall be in writing and shall require the assent of at least three members. SECT. 7. An applicant for a permit whose application has been refused may appeal therefrom within ninety days. A person who has been ordered by the commissioner to incur any expense may within ten days after being notified of such order appeal therefrom by giving to the commissioner notice in writing of his appeal. Such notice or a certified copy thereof shall at once be transmitted by the commissioner to the board of appeal. After notice given to such parties as the board shall order, a hearing shall be had, and the board shall affirm, annul, or modify said refusal or order. The board may vary the provisions of this act in specific cases which appear to them not to have been contemplated by this act although covered by it, or in cases where manifest injustice is done, provided that the decision of the board in such a case shall be unanimous and shall not conflict with the spirit of any provision of this act. The decision shall specify the variations allowed and the reasons there- for, and shall be filed in the office of the commissioner within ten days after the hearing. A certified copy shall be sent by mail or otherwise to the applicant and a copy kept publicly posted in the office of the com- missioner for two weeks thereafter. If the order or refusal of the com- missioner is affirmed, such order or refusal shall have full force and effect. If the order or refusal is modified or annulled, the commissioner shall issue a permit in accordance with such decision. The provisions of this section shall also apply to any similar action or order of the commissioner of wires, under the provisions of chapter two hundred and sixty-eight of the acts of the year eighteen hundred and 6 Acts of 1907, Chapter 550. ninety-eight, or of any amendment thereof or addition thereto, except that in respect thereto the words " commisioners of wires " shall be sub- stituted for the word " commissioner." SECT. 8. Methods of construction or maintenance equivalent to those required by the provisions of this act may be allowed with the written consent of the commissioner and the board of appeal specifying the same. A record of the required and the equivalent method allowed shall be kept in the office of the commissioner. It shall be the duty of the board of appeal to submit to the mayor on or before the first day of February in each year a report giving a sum- mary of all decisions of the board, together with such recommendations for revision of the law as may seem to them advisable. The commis- sioner shall cause the report to be printed as a separate document for public distribution. Any requirement necessary for the strength or stability of any pro- posed structure or for the safety of the occupants thereof, not specifically covered by this act, shall be determined by the commissioner, subject to appeal. SECT. 9. The building limits of the city of Boston as they now exist shall continue until changed by ordinance, and the city council may by ordinance from time to time extend and define said building limits, and may establish other limits in any part of the city within which every building built after the establishment thereof shall be of the first or second class. This restriction shall not apply to wharves, nor to build- ings not exceeding twenty-seven feet in height on wharves, nor to market sheds or market buildings not exceeding such height, nor to elevators for the storage of coal or grain, if the external parts of such buildings, elevators, or other structures are covered with slate, tile, metal, or other equally fireproof material, and the mode of construction and the location thereof are approved by the commissioner. Temporary structures to facilitate the prosecution of any authorized work may be erected under such conditions as the commissioner may prescribe. SECT. 10. The provisions of this act shall not apply to bridges, quays, or wharves,, nor to buildings on land ceded to the United States or owned and occupied by the Commonwealth, nor to the Suffolk County court house, jail, or house of correction, nor to railroad stations, nor to portable school buildings erected and maintained by the schoolhouse department, nor to voting booths erected and maintained by the board of election commissioners. Except as otherwise provided by law, the provisions of this act shall not be held to deprive the board of health, the police commissioner, the board of street commissioners, the board of park commissioners, the board of examiners of gas fitters, the commissioner of wires, or the fire commissioner of the city of Boston of any power or authority which they have at the date of the passage of this act, or of the remedies for the enforcement of the orders of said boards or officers; unless such powers, authorities, or remedies are inconsistent with the provisions of this act ; nor to repeal any existing law, not herein expressly repealed, except so far as it may be inconsistent with the provisions of this act. Acts of 1907, Chapter 550. DEFINITIONS. SECT. 11. In this act the following terms shall have" respectively assigned to them: First class building: A first class building shall consist of fireproof material throughout, with floors constructed of iron, steel or reinforced concrete beams, filled in between with terra-cotta or other masonry arches or with concrete or reinforced concrete slabs; wood may be used only for under and upper floors, windows and door frames, sashes, doors, interior finish, hand rails for stairs, necessary sleepers bedded in the cement, and for isolated furrings bedded in mortar. There shall be no air space between the top of any floor arches and the floor boarding. Second class building: All buildings not of the first class, the ex- ternal and party walls of which are of brick, stone, Iron, steel, concrete, reinforced concrete, concrete blocks, or other equally substantial and fireproof material. Third class building: A wooden frame building. Composite building: A building, partly of second class and partly of third class construction. Foundation: That part of a wall below the level of the street curb, or, if a wall is not on a street, that part of the wall below the level of the highest ground next to the wall, or, if so construed by the commissioner, that part of a party or partition wall below the cellar floor. Height of a building: The vertical distance of the highest point of the roof above the mean grade of the curbs of all the streets upon which it abuts, and if it does not abut on a street, above the mean grade of the ground adjoining the building. Party wall : A wall that separates two or more buildings, and is used or adapted for the use of more than one building. Partition wall : An interior wall of masonry in a building. Thickness of wall: The minimum thickness of such wall. Story of a building : That part of a building between the top of any floor beams and the top of the floor or roof beams next above. Basement : That story of a building not more than forty per cent of which is below the grade of the street. Cellar: That part of a building more than forty per cent of which is below the grade of the street, and in third class buildings that part of the building which is below the sills. Gas fitting shall mean the work of putting together any fittings, pipe or fixtures or other appliances which are to contain gas for heat, light or power purposes and will be subject to inspection under existing laws. REQUIREMENTS FOR ALL BUILDINGS. SECT. 12. No building, structure or foundation shall be constructed or altered without a permit, and such work shall be done in accordance with drawings bearing the approval of the commissioner. Every structure in process of construction, alteration, repair or re- moval, and every neighboring structure or portion thereof affected by such process or by any excavation, shall be sufficiently supported during such process. 8 Acts of 1907, Chapter 550. The commissioner may take such measures as the public safety re- quires to carry these provisions into effect. All buildings shall have leaders sufficient to discharge the roof water in such a manner as not to flow upon any public way or any neighboring property. Such leaders may project into a public way not over seven inches. Every chimney flue shall be carried to a height sufficient to protect adjoining buildings from fire and smoke, and, unless the roof is covered with incombustible material, shall extend at least four feet above the highest point of contact with the roof. Every permanent building more than twenty feet high having a flat roof shall have permanent means of access to the roof from the inside by an opening not less than two feet by three feet, with a fixed step- ladder. Every building shall have, with reference to its height, condition, con- struction, surroundings, character of occupation and number of occu- pants, reasonable means of egress in case of fire, satisfactory to the commissioner, except that in all factories or workshops hereafter built or altered, of second class construction, where ten or more persons are employed above the second floor, one exit shall consist of a fireproof stairway enclosed in incombustible material. Water pipes in every building shall be properly protected from frost. All chimneys of masonry construction shall have walls at least eight inches thick, or be constructed of four-inch brick walls with a suitable flue lining. Every building used for habitation shall have such number of water- closets as the board of health may require; every building where persons are employed shall have at least one water-closet for every twenty persons therein employed, and in any building where both sexes are employed, separate accommodations shall be furnished for men and women. Every enclosure containing one or more water-closets shall be provided with adequate ventilation to the outer air either by window or by suitable light shaft. In every first and second class building all of the outside finish shall be of incombustible material, except window and door frames, and except finish about show windows in the first story. Where store fronts are carried up more than one story the columns and lintels shall be of, or fin- ished with, incombustible material; but in no case shall store fronts be car- ried more than two stories'unless the same are constructed and finished throughout with fireproof material, except window and door frames. Every ventilating flue shall be constructed of, or lined with, incom- bustible material. Every floor in second class buildings shall have its beams tied to the walls and to each other with wrought-iron straps or anchors at least three eighths of an inch thick by one and one half inches wide, and not less than eighteen inches long, so as to form continuous ties across the building not more than ten feet apart. Walls running parallel, or nearly parallel, with floor beams shall be properly tied once in ten feet to the floor beams by iron straps or anchors of the size above specified. Every wooden header or trimmer more than four feet long, carrying a floor load of over seventy pounds per square foot, shall, at connections with other beams, be framed or hung in stirrup irons, and joint-bolted. Acts of 1907, Chapter 550. 9 All tail beams and similar beams of wood shall be framed or hung in stirrup irons. PROHIBITIONS. SECT. 13. No alteration or repair of a wooden building within the building limits shall be made without a permit from the commissioner, and no permit to increase the height or ground area of such a building shall be granted, nor shall a permit for alterations or repairs be granted if the estimated cost of the proposed alterations or repairs exceeds one half of the cost of a like new building. No wooden building, within or without the building limits, shall be moved to any position within the building limits. No recess or chase shall be made in any external or party wall so as to leave the thickness at the back less than eight inches. No roof or floor timber entering a party wall shall have less than four inches of solid brickwork between it and the end of any other timber. No part of any roof shall be constructed in such a manner as to dis- charge snow, ice, or other material upon a public street or alley. No elevated staging or stand for observation purposes shall be con- structed or occupied upon the roof of any building. No chimney shall be corbelled from a wall more than the thickness of the wall. No chimney shall be hung from a wall which is less than twelve inches thick. No masonry shall rest upon wood, except piles and mud sills. No part of any floor timber shall be within two inches of any chimney. No studding or furring shall be within one inch of any chimney. No furnace or boiler for heating shall be placed upon a wooden floor. No smoke pipe shall project through any external wall or window. No steam, furnace, or other hot air pipes shall be carried within one inch of any woodwork, unless such pipes are double or otherwise pro- tected by incombustible material. No observation stand shall be constructed or maintained except in accordance with plans approved by the commissioner. No closet of any kind shall be constructed under any staircase leading from the cellar or basement to the first story. No boiler shall be placed or maintained under any public way. No part of any structure, except cornices, permanent awnings, string courses, window caps and sills, bay windows, under such terms, con- ditions, regulations and restrictions as may be required by the mayor and board of aldermen, and outside means of egress, as otherwise pro- vided, and signs as provided in chapter three hundred and fifty-two of the acts of the year eighteen hundred and ninety-five, shall project over any public way or square. No cornice or bay window shall so project more than three feet; nor more than twelve inches over a way of a width of thirty feet or less. No building within forty feet of the property of any adjoining owner shall be erected for or converted to use as a stable, unless such use is authorized by the board of health after a public hearing. Written notice of such hearing shall be given to the adjoining owners, and pub- lished at least three times in at least two newspapers published in Boston, ten days at least before the hearing. 10 Acts of 1907, Chapter 550. MATERIALS. Strength of Materials. SECT. 14. The stresses in materials hereafter used in the construc- tion of all buildings, produced by their own weight and the loads herein specified, shall not exceed the limits assigned in the following paragraphs of this section : (a) TIMBER. Unit Stresses in Pounds per Square Inch. On Extreme Fibre of Beams. Shearing along the Grain. Compression Perpendicular to the Grain. White pine and spruce 1 000 80 250 White oak, 1,000 150 600 Yellow pine (long-leaved), .... 1,500 100 500 Stresses due to transverse loads combined with direct tension or com- pression shall not exceed the extreme fibre stresses given above. In computing deflection, the modulus of elasticity shall be taken as follows : Pounds per Square Inch. White pine, 750,000 Spruce, 900,000 Yellow pine (long-leaved), 1,300,000 White oak ............ 850,000 Columns (centrally loaded). For wooden columns with flat ends, where L is the length of the col- umn, D is its least diameter, the average stress per square inch on a cross-section shall be limited as follows : AVERAGE STRESS PER SQUARE INCH. L D White Pine and Spruce. Long-leaved Yellow Pine. White Oak. to 10, 630 900 810 10 to 15 ... 595 850 765 15 to 20 560 800 720 20 to 25, 525 750 675 25 to 30 490 700 630 No column shall be used with a greater unsupported length than thirty times its least diameter. For excentric loads see section sixteen. Acts of 1907, Chapter 550. 11 (6) WROUGHT IRON AND STEEL. Unit Stresses in Pounds per Square Inch. Wrought Iron. Steel. 1 Extreme fibre of rolled beams or shapes, Tension, 12,000 12,000 16,000 16,000 Compression in flanges of built beams, . . . Shearing (see below for bolts), . Direct bearing including pins and rivets 12,000 9,000 15,000 16,000 10,000 18,000 Bending on pins, 18,000 22,500 Modulus of elasticity 27,000,000 29,000,000 For compression members twelve thousand for iron and sixteen thou- sand for steel, reduced according to the following formula: 12,000 (or 16,000 for steel). 1 L 2 1 + - 20,000 r 2 in which L is the length of the column in inches, and r is the radius of gyration in inches taken around the axis about which the column will bend (for free columns, the least radius of gyration). The stresses due to transverse loads combined with direct tension or compression shall not exceed the extreme fibre stress given above for rolled beams and shapes, or in case of built members the above tension and compression stresses (see section sixteen). Compression flanges of beams shall be proportioned to resist lateral flexure unless properly stayed or secured against it. If the ratio of unsupported length of flange to width of flange does not exceed twenty, no allowance need be made for lateral flexure. If the ratio is seventy the allowable stress on the extreme fibre shall be one half of that above specified, and proportionally for intermediate ratios. Shearing and bearing stresses on bolts shall not be higher than eighty per cent of those allowed by the above table. All connections in skeleton buildings, all splices in steel trusses and girders, and all connections of such trusses and girders to the sides of steel columns shall, if possible, be made by means of rivets rather than by bolts. (c) CAST IRON. Unit Stresses in Pounds per Square Inch. Extreme fibre stress, tension, 3,000 Extreme fibre stress, compression, 16,000 Cast iron shall not be used for columns in buildings of more than 1 These stresses (except for rivets) are for steel having an ultimate tensile strength of from fifty- five thousand to sixty-five thousand pounds per square inch, an elastic limit of not less than one half the ultimate strength, and a minimum percentage of elongation in eight inches of one million four hundred thousand, divided by the ultimate strength. 12 Acts of 1907, Chapter 550. seventy-five feet in height, nor in cases where the value of the length divided by least radius of gyration exceeds seventy. Cast Iron Columns (centrally loaded and unsupported laterally). Where the Length divided by the Least Radius of Gyration equals Average Stress per Square Inch of Section. Where the Length divided by the Least Radius of Gyration equals Average Stress per Square Inch of Section. 10 20 30 40 11,000 10,700 10,400 10,000 50 60 70 9,800 9,500 9,200 (d} STONE WORK, IN COMPRESSION. Stresses in Tons of Two Thousand Pounds per Square Foot. First quality dressed beds and builds, laid solid in mortar of one part Portland cement to three parts sand, or one part natural cement to two parts sand. Granite, ........................ 60 Marble and limestone, .................. 40 Sandstone, ....................... 30 In cases where poorer mortar is used, to avoid stain from cement, stresses shall be less than above, and must be approved by the building commissioner. (e} BRICKWORK IN COMPRESSION. Stresses in Tons of Two Thousand Pounds per Square Foot. (1.) For first class work of hard-burned bricks, including piers in which the height does not exceed six times the least dimension, laid in: (a) One part Portland cement, three parts sand, by volume, dry, ....... 20 (6) One part natural cement, two parts sand, by volume, dry, ........ 18 (c) One part natural cement, one part lime and six parts sand, by volume, dry, 12 (d) Lime mortar, one part lime, six parts sand, by volume, dry, ....... 8 (2.) For brick piers of hard-burned bricks, in which the height is from six to twelve times the least dimension : Mortar (a), . ................ ..... 18 Mortar (6), ...... ................ 15 Mortar (c), ...................... 10 Mortar (d), ...................... 7 (3.) For brickwork made of " light-hard " bricks, the stresses shall not exceed two thirds of the stresses for like work of hard-burned bricks. (/) CONCRETE. When the structural use of concrete is proposed, a specification, stating the quality and proportions of materials, and the methods of mixing the same, shall be submitted to the building commissioner, who may issue a Acts of 1907, Chapter 550. 13 permit at his discretion and under such further conditions, in addition to those stated below, as he sees fit to impose. A. In first class Portland cement concrete, containing one part cement to not more than six parts mixed properly graded aggregate, except in piers or columns of which the height exceeds six times the least dimension, the compressive stress shall not exceed thirty tons of two thousand pounds per square foot. B. In piers and columns of first class Portland cement concrete, con- taining one part cement to not more than five parts mixed properly graded aggregate, where the height of the pier or column is more than six times and does not exceed twelve times its least dimension, the com- pressive stress shall not exceed twenty-five tons of two thousand pounds per square foot. By " aggregate " shall be understood all the materials in the concrete except the cement. Cinders concrete shall be used constructively only for floors, roofs, and for filling. Rules for the computation of reinforced concrete columns may be for- mulated from time to time by the building commissioner with the approval of the board of appeal. In reinforced concrete beams or slabs subjected to bending stresses, the entire tensile stress shall be assumed to be carried by the steel, which shall not be stressed above the limits allowed for this material. First class Portland cement concrete in such beams or slabs, containing one part cement to not more than five parts mixed properly graded aggregate, may be stressed in compression to not more than five hun- dred pounds per square inch. In case a richer concrete is used, this stress may be increased with the approval of the commissioner to not more than six hundred pounds per square inch. In reinforced concrete the maximum shearing force upon the concrete, when uncombined with compression upon the same plane shall not ex- ceed sixty pounds per square inch, unless the building commissioner with the consent of the board of appeal shall fix some other value. If the imbedded steel has no mechanical bond with the concrete, its holding power shall not exceed the allowable shearing strength of the concrete. (0) IN GENERAL. Under the prescribed loads, beams shall be so proportioned that the deflection shall not exceed one three hundred and sixtieth (3^) of the span. Stresses for materials and forms of material, not herein mentioned, shall be determined by the building commissioner. Provision for wind bracing shall be made wherever it is necessary, and all buildings shall be constructed of sufficient strength to bear with safety the load intended to be placed thereon, in addition to the weight of the materials used in construction. No cutting for piping or any other purpose shall be done which would reduce the strength of any part of the structure below what is required by the provisions of this act. 14 Acts of 1907, Chapter 550. Quality of Materials. SECT. 15. All materials shall be of such quality for the purposes for which they are to be used as to insure, in the judgment of the building commissioner, ample safety and security to life, limb and neighboring property. The building commissioner shall have power to reject all materials which in his opinion are unsuitable, and may require tests to be made by the architect, engineer, builder or owner to determine the strength of the structural materials before or after they are incorporated in a building, and may require certified copies of results of tests made elsewhere from the architect, engineer, builder, owner or other interested persons. Hollow cast iron columns, if used, shall be shown by measurements and tests satisfactory to the commissioner to be of practically uniform thickness, and free from blow holes. MORTARS. All mortars shall be made with such proportion of sand as will insure a proper degree of cohesion and tenacity, and secure thorough adhesion to the material with which they are used, and the building commissioner shall condemn all mortars not so made. (a) Mortar below the level of water shall be no poorer than one part Portland cement and three parts sand; (6) Mortar for first class buildings shall, for the lower half of their height, be no poorer than one part natural cement to two parts sand; and, for the upper half, no poorer than one part of natural cement, one half part of lime, and three parts of sand ; * (c) Mortar for second class buildings and for such parts of third class buildings as are below the level of the sidewalk, shall be no poorer than one part of natural cement, one of lime, and four of sand; (d) Mortar for third class buildings, above ground, shall be no poorer than one part lime and four parts sand. The building commissioner may allow lime mortar in setting stone where cement will stain. CONCRETE. Concrete shall be used immediately after mixing; it shall not be placed in the work after it has begun to harden; and it shall be deposited in such manner and under such regulations as to secure a compact mass of the best quality for the proportions used. Forms shall remain until the concrete has hardened so as to be able to carry its load safely, and shall be removed without jar. The commissioner may require an applicant for a permit for the structural use of concrete to have an inspector satisfactory to the com- missioner at all times on the work while concrete is being mixed or de- posited, and such inspector shall make daily reports to the commissioner on the progress of the work. CEMENT. Cement shall conform to the specifications of the American Associa- tion for Testing Materials, as modified from time to time by that association. Acts of 1907, Chapter 550. 15 REINFORCED CONCRETE. Reinforced concrete slabs, beams or girders, if rendered continuous over supports by being unbroken in section, shall be provided with proper metal reinforcement at the top over said supports and may be computed as continuous beams, as hereinafter described. The modulus of elasticity of the concrete, if not shown by direct tests, may for beams and slabs be taken as one fifteenth that of steel, and for columns one tenth that of steel. The reinforcing metal shall be covered by not less than three fourths inch of concrete in slabs, and by not less than one and one half inches of concrete in beams and columns. METHODS OF COMPUTATION. SECT. 16. Beams or girders of metal or reinforced concrete shall be considered as simply supported at their ends, except when they extend with unbroken cross-section over the supports, in which case they may be considered as continuous. The span of a beam shall be considered as the distance from center to center of the bed plates or surfaces upon which it rests. If it is fastened to the side of a column, the span shall be measured to the centre of the column. In slabs, beams or girders continuous over supports, provision shall be made for a negative bending moment at such supports equal to four fifths of the positive bending moment that would exist at the centre of the span if the piece were simply supported; and the positive bending moment at the centre of the span may be taken equal to the negative bending moment at the support. In the case of a slab of reinforced concrete with parallel ribs or girders beneath, the rib or girder may be considered to include a portion of the slab between the ribs, forming a T-beam. The width of the T-beam on top shall not exceed one third the span of the rib nor the distance from centre to centre of the ribs. Reinforced concrete columns shall be proportioned on the assumption that the concrete and the steel are shortened in length in the same pro- portion. The steel members shall be tied together at intervals suffi- ciently short to prevent buckling. If a column is loaded excentrically or transversely, the maximum fibre stress, taking account of the direct compression, the bending which it causes, its excentricity and the transverse load, shall not exceed the maximum allowable stress in compression. If a tension piece is loaded excentrically or transversely, the maximum fibre stress, taking account of the direct tension, its excentricity and the transverse load, shall not exceed the maximum allowable stress in tension. An excentric load upon a column shall be considered to affect excentri- cally only the length of column extending to the next point below at which the column is held securely in the direction of the excentricity. If a piece is exposed to tension and compression at different times, it shall be proportioned to resist the maximum of each kind, but the unit stresses shall be less than those used for stress of one kind, depending upon the ratio and the relative frequence of the two maxima. 16 Acts of 1907, Chapter 550. Net sections shall be used in proportioning steel tension members, and in deducting rivet holes they shall be taken as one eighth of an inch greater in diameter than the rivets. The length of a steel compression member between supports in any direction shall not exceed one hundred and twenty times its radius of gyration about an axis perpendicular to that direction. The webs of plate girders shall be proportioned to resist buckling in cases where they are not supported laterally, according to the formula : 15,000 1 d 2 3,000 t 2 in which t = thickness of web, in inches; d = clear, unsupported dimen- sion horizontally or vertically, whichever is the lesser. In proportioning the flanges of plate girders, one eighth of the gross area of the web may be considered as available in each flange. If the length of the top flange unsupported laterally exceeds twenty times its width, the allowable stress shall be reduced, as in the case of rolled beams. Pins shall be computed by assuming the forces in the bars to act at the centre of the bearing areas. In riveted trusses the centre of gravity lines of members coming to- gether at a joint shall, if possible, intersect at a point. Excentricity due to a non-fulfillment of this rule shall be allowed for in the computations. The centre of gravity of the rivets connecting one piece to another shall, in general, lie as nearly as practicable in the centre of gravity line of the piece. CLASSIFICATION. First and Second Class Buildings. SECT. 17. Every building over seventy-five feet in height hereafter erected or raised and every house adapted for habitation more than five stories in height and exceeding sixty-five feet above the basement or covering more than five thousand superficial square feet on the ground floor, regardless of height, shall be constructed as a first class building; and all other houses may, except as herein otherwise provided, be of second or third class construction. New buildings adapted for habitations, and not more than five stories above the cellar or basement, may be erected of second class construc- tion, but no such building shall exceed five thousand square feet in super- ficial area or sixty-five feet in height. The first story or basement, or both the first story and basement, in such buildings, so constructed, altered, remodelled or enlarged, may be used for mercantile purposes, provided, that the walls and ceilings surrounding the areas so used shall be fire-stopped to the satisfaction of the commissioner. New buildings, of concrete, concrete blocks or brick, not over three stories in height, adapted for the occupancy of a single family and having a superficial area of not more than twelve hundred square feet, may be constructed with external and party or division walls of eight inches in thickness: provided, however, that where the party wall of a building thus constructed joins or becomes the party wall of another Acts of 1907, Chapter 550. 17 such building, the floor timbers in each of such buildings shall be so spaced or protected that their ends shall not approach nearer than within eight inches of each other. Restriction of Areas. Any first class building used above the first floor as a warehouse or store for the storage or sale of merchandise shall have all vertical open- ings protected by fireproof enclosures. Such enclosures shall, if enclos- ing stairs or escalators, have automatic doors, and all glass in said enclosure shall be wire glass. Such buildings shall so be divided by brick walls built like party walls with the same openings allowed, that no space inside such buildings shall exceed in area ten thousand square feet, except that when any such building has a frontage of not less than fifty feet on each of two streets, such space may exceed ten thousand square feet in area, provided that buildings in which such extension of area beyond ten thousand square feet is permitted shall have automatic fire sprinklers installed, and means of ingress and egress satisfactory to the commissioner and the board of appeal. Second class buildings used above the first floor as warehouses or stores for the storage or sale of merchandise shall so be divided by brick walls, built like party walls with the same openings allowed, that no space inside such buildings shall exceed in area ten thousand square feet, and no existing wall in any second class building shall be removed so as to leave an area of more than ten thousand square feet, nor shall any exist- ing wall, separating areas which combined would exceed ten thousand square feet in area, have openings cut in it greater in area or number than is allowed by this act for party walls. Every second class building more than three stories high and used above the first floor as a warehouse or store for the storage or sale of merchandise shall have all vertical openings for elevators and stairways, air or light shafts, through its floors protected by fireproof enclosures. Such enclosures shall be supported on fireproof supports and framing, and shall, if enclosing stairs or escalators, have automatic doors, and all glass in said enclosures shall be wire glass. No building used above the first floor for the storage or sale of mer- chandise shall have less than two means of egress from every story, one of which means may be either an outside fire escape or through a brick wall closed by automatic doors into a building of the same class; except that an independent monumental stairway extending from the basement to the second floor may be constructed. Buildings for Manufacturing Purposes. Buildings outside the building limits and adapted exclusively for manufacturing, storage, mechanical or stable purposes, may be built under such conditions as the commissioner shall prescribe. If of wood such buildings shall not exceed forty-five feet in height. 18 Acts of 1907, Chapter 550. CONSTRUCTION. Height. SECT. 18. No building, structure or part thereof shall be of a height exceeding two and one half times the width of the widest street on which the building or structure stands, whether such street is a public street or place or a private way, nor exceeding one hundred and twenty-five feet in any case. The width of such street, place or private way shall be measured from the face of the building or structure to the line of the street on the other side. If the street is of uneven width, the width shall be the average width of the part of the street opposite the building or structure; if the effective width of the street is increased by an area or setback, the space between the face of the main building and the law- fully established line of the street may be built upon to the height of two and one half times the width of the street. All buildings or structures hereafter erected in any part of the city shall be subject to the restrictions imposed by chapter four hundred and fifty-two of the acts of the year eighteen hundred and ninety-eight, by chapter five hundred and forty-three of the acts of the year nineteen hundred and two, by chapter three hundred and eighty-three of the acts of the year nineteen hundred and five, and by chapter four hundred and sixteen of the acts of the year nineteen hundred and seven, so far as the restrictions imposed by said acts relate to the districts described therein; and shall also be subject to any restrictions lawfully imposed by the park commissioners of said city. Excavations. SECT. 19. All excavations shall so be protected, by sheet piling if necessary, by the persons causing the same to be made, that the adjoining soil shall not cave in by reason of its own weight. It shall be the duty of the owner of every building to furnish, or cause to be furnished, such support that his building shall not be endangered by any excavation: provided, that the owner of any building which is endangered by an excavation carried by an adjoining owner more than ten feet below the grade of the street may recover the expense so caused of supporting such building from the persons causing such excavation to be made. All per- manent excavations shall be protected by retaining walls. In case of any failure to comply with the provisions of this section the commis- sioner may enter upon the premises and may furnish such support as the circumstances may require. Any expense so incurred may be recovered by the city from the persons required by law to furnish the support. Piling. SECT. 20. All buildings shall, if the commissioner determines that piling is necessary, be constructed on foundation piles which, if of wood, shall be not more than three feet apart on centres in the direction of the wall, and the number, diameter and bearing of such piles shall be suffi- cient to support the superstructure proposed. The commissioner shall determine the grade at which the piles shall be cut. The commissioner may require any applicant for a permit to ascertain by boring the nature of the ground on which he proposes to build, and he may require an Acts of 1907, Chapter 550. 19 inspector satisfactory to the commissioner to be at all times on the work while piles are being driven, who shall keep an accurate record of the length of each pile, the weight and fall of the hammer, and the penetra- tion of each pile for each of the last two blows of the hammer. Plain concrete piles shall be made in place by methods which are rea- sonably certain to secure perfect, full sized piles. Reinforced concrete piles if properly designed to resist the shock of driving, and if driven with a cushion to lessen the shock or by a water jet, may be molded, allowed to harden, and then driven in place. In case concrete piles are used, whether reinforced or not, their bearing power shall be determined by putting in one or more test piles and loading them after the concrete has hardened. The load allowed shall not be more than one half the load under which the pile begins to settle. In no case, however, shall the load on a concrete pile exceed that specified herein for concrete in columns. Concrete for piles shall have not more than five parts of properly made and mixed aggregate to one part of Portland cement; and the aggregate shall all be capable of passing through a one inch ring. All wood piles shall be capped with block granite levellers, each leveller having a firm bearing on the pile or piles which it covers, or with first class Portland cement concrete, not less than sixteen inches thick, above the pile caps, containing one part of cement to not more than six parts of properly graded aggregate of stone and sand, the concrete to be filled in around the pile heads upon the intervening earth. Foundations of First and Second Class Buildings. SECT. 21. Foundations of first and second class buildings may be of brick, stone or concrete. The thickness shall be as stated in section twenty-three. Foundations of rubble stone shall be allowed only under buildings less than forty-five feet in height and for a depth of less than ten feet. The walls and piers of every building shall have a foundation, the bearing of which shall be not less than four feet below any adjoining surface exposed to the frost, and such foundation, with the superstruc- ture which it supports, shall not overload the material on which it rests. Cellars. SECT. 22. The cellar of every building, where the grade or nature of the ground so requires, shall be sufficiently protected from water and damp by a bed at least two inches thick over the whole, of concrete, cement and gravel, tar and gravel, or asphalt, or by bricks laid in cement. No cellar or basement floor of any building shall be constructed below the grade of twelve feet above mean low water, unless such cellar is made waterproof to the satisfaction of the commissioner. All metal founda- tions and all constructional metal work underground shall be protected from dampness by concrete, or by other material approved by the commissioner. Thickness of Walls. SECT. 23. Except as provided in section seventeen, the external walls above the foundation of houses for habitation of first or second class con- struction, and not exceeding sixteen hundred square feet in area and not CM ENGINEERING 20 Acts of 1907, Chapter 550. over three stories high, shall be not less than eight inches thick for external walls and not less than twelve inches thick for party walls. In case any part of such building is adapted for any use other than habita- tion, all walls shall be not less than twelve inches thick. All other houses for habitation, not exceeding five thousand feet in superficial area and not exceeding five stories or sixty-five feet in height, above the base- ment, shall have all walls not less than twelve inches thick. The external and party walls of every building of the first or second class, except houses for habitation, less than sixty-five feet in height shall be twelve inches thick in the upper two stories not exceeding twenty-five feet in height. In the section of two stories, but not exceeding twenty- five feet next below, the walls shall be sixteen inches thick. In the next lower section of three stories, but not exceeding thirty-seven feet, the walls shall be twenty inches thick, and in each succeeding section of three stories, but not exceeding thirty-seven feet or any part thereof, the walls shall be four inches thicker than the section next above it. The founda- tion walls shall be at least four inches thicker than the required thickness of the walls of the first story. The thickness herein given shall apply to all masonry walls unless they are reinforced by a frame or skeleton of steel. In reckoning the thickness of walls, ashlar shall not be included unless the walls are at least sixteen inches thick and the ashlar is at least eight inches thick, or unless alternate courses are at least four and eight inches to allow bonding with the backing. Ashlar shall be properly held by metal clamps to the backing or properly bonded to the same. Anchors. SECT. 24. All walls of a first or second class building meeting at?an angle shall be securely bonded, or shall be united every five feet of their height by anchors made of at least two inches by half an inch of steel or wrought iron, well painted, and securely built into the side or partition walls not less than thirty-six inches, and into the front and rear walls at least one half the thickness of such walls. Brickwork Bonding. SECT. 25. Every eighth course, at least, of a brick wall shall be a full heading or bonding course, except where walls are faced with face brick, in which case in every eighth course at least every other brick shall be a full header. No diagonal header ties shall be used. Vaulted Walls. SECT. 26. If the air spaces are headed over and the walls are built solid for at least three courses below the floor and roof beams, walls, if of brick, may be built hollow. They shall contain, exclusive of withes, the same amount of material as is required for solid walls, and the masonry on the inside of the air space in walls over two stories in height shall be not less than eight inches thick, and the parts on either side shall be securely tied together with ties not more than two feet apart in each direction. Acts of 1907, Chapter 550. 21 Walls Framed with Iron or Steel. SECT. 27. Walls may be built in part of iron or steel or with a reinforced concrete or metal framework. In such metal framework the beams and girders shall be riveted to each other at their respective junc- tion points. If columns made of rolled iron or steel are used, their different parts shall be riveted to each other, and the beams and girders resting upon them shall, if possible, have riveted connections to unite them with the columns. If cast iron columns are used, each successive column shall be bolted to the one below it by at least four bolts not less than three fourths of an inch in diameter, and the beams and girders shall be bolted to the columns. At each line of floor or roof beams, lat- eral connections between the ends of the beams and girders shall be made in such manner as rigidly to connect the beams and girders with each other in the direction of their length. All party walls of skeleton construction shall have curtain walls of brick, not less than twelve inches thick. All outside walls of skeleton construction shall have curtain walls which may be of masonry, terra-cotta, concrete, or reinforced concrete, constructed and supported under such conditions as the commissioner shall prescribe. If the metal or other framework is so designed that the enclosing walls do not carry the weight of floors or roof, then the walls shall be of ma- sonry or concrete construction and shall be thoroughly anchored to the iron skeleton, and whenever the weight of such walls rests upon beams or columns, such beams or columns shall be made strong enough in each story to carry the weight of wall resting upon them without reliance upon the walls below them. Party Walls Above Roof. SECT. 28. In buildings less than forty-five feet in height all party walls shall be built to a height at least twelve inches above the roof covering, and shall be capped with stone, cement or metal securely fas- tened to the masonry. In all other buildings such walls shall be carried thirty inches above the roof. Walls Cornices. SECT. 29. Where a wall is finished with a stone cornice, the greatest weight of material of such cornice shall be on the inside of the face of the wall. All cornices of second class buildings shall be of brick or covered with fireproof material, and the walls shall be carried up to the boarding of the roof; and where the cornice projects above the roof the masonry shall be carried up to the top of the cornice and covered with metal, like parapet walls. Piers and Hearths. SECT. 30. Piers and walls shall have caps or plates, where they are needed, sufficient properly to distribute the load. Hearths shall be supported by trimmer arches of brick or stone; or shall be of single stones at least six inches thick, built into the chimney 22 Acts of 1907, Chapter 550. and supported by iron beams, one end of which shall be securely built into the masonry of a chimney or of an adjoining wall, or which shall otherwise rest upon an incombustible support. Brick jambs of every fireplace, range or grate opening shall be at least eight inches wide each, and the backs of such openings shall be at least eight inches thick. Hearths and trimmer arches shall be at least twelve inches longer on either side than the width of such openings, and at least eighteen inches wide in front of the chimney breast. Brickwork over fireplaces and grate openings shall be supported by proper iron bars, or brick or stone arches. Walls Doorways in Party Walls. SECT. 31. Openings for doorways in party walls shall not exceed one hundred square feet each in area, and each opening shall have two sets of fire doors separated by the thickness of the wall, hung in a manner satisfactory to the commissioner, except that the aggregate width of all openings in any story shall not exceed fifty per cent of the length of the wall in which such openings occur. Openings, not exceeding one hundred and forty-four square inches, constructed and protected as shall be approved by a writing signed by the fire commissioner, and filed with the commissioner, may be permitted in any wall or floor. Fire Protection. SECT. 32. All structural metal supporting or forming part of the frame, floors, roof or columns of any building, except as otherwise ex- empted in this act, shall be protected against the effect of heat. This protection shall consist of concrete, or of porous terra-cotta or brick set in cement mortar. When block construction is used, it shall be clamped in place with steel clamps, or wrapped securely with number twelve galvanized-iron wire or metal lathing in such manner as to hold each block in place, and shall be plastered with lime or other mortar at least three fourths of an inch thick in addition to the protection. The protection on all floor and roof beams shall be at least one inch thick, on all floor and roof girders and on all beams carrying masonry at least one inch thick on top and two inches thick elsewhere, on all columns carrying only floors three inches, and on all columns built into or carrying walls four inches. If terra-cotta blocks are used for protection, such blocks may be hol- low, but each face shall be solid, and no flange shall be less than one inch thick. Plaster on wire or metal lath shall not be considered as a fire protection for steel or iron structural members, but may be used with an air space under arches as a suspended ceiling, provided that such arches have at least one inch of thickness of fireproofing under the flanges in addition to such ceiling, and that the metal lath and plaster are suspended sep- arately from the arches and are not less than one inch below the same. All protection shall be applied directly to the metal work and shall not be broken into nor interrupted by any pipes, wires, chases or conduits of any kind. About isolated columns on the exterior of buildings, the thickness of protection may be reduced to one inch, when the same is covered with an outer shell of cast iron or steel. When a column or girder is formed of built-up shapes, the spaces Acts of 1907, Chapter 550. 23 between flanges shall be filled solid with protecting material, but this protection need not extend more than one inch beyond the edges of projecting angles, bars or channels. The protection shall cover all lugs, brackets, braces, etc. The metal work of all trusses carrying masonry or floor loads shall be protected, as hereinbefore described, but said provisions shall not apply to trusses which carry roof load only. When a wall or partition is formed with a framework of angles, chan- nels, or other built-up shapes, and such wall or partition is filled in flush with both faces of the frame with terra-cotta blocks, additional pro- tection may be omitted. The above requirements as to fireproofing shall not apply to iron or steel in second or third class buildings in any case in which the use of wood without fire protection would be permissible under this act. In work in connection with alterations of existing buildings, the char- acter and amount of protection for steel and ironwork shall be made satisfactory to the commissioner. In positions where the protection of isolated or exposed columns is likely to be broken or damaged by trucks or merchandise, there shall be outside of the protection a guard at least five feet high of iron or wood, bound with wire or steel so as to be self-supporting. Spaces between and behind all studding or furring shall be filled solid with bricks and mortar or other fireproof material for a space of five inches in height above the floor beams or plaster grounds. Spaces between the strap furring on brick walls shall be filled solid with mortar for five inches below the bottom of the floor beams. The spaces between stringers of stairs and joists of landings, unless unceiled or of fireproof construction, shall be stopped solid with wood, brick or terra-cotta or other approved material as often as twice in each flight of stairs. The spaces between floor beams on bearing partitions shall be stopped in a similar manner. In every building of second or third class construction each floor shall be thoroughly stopped by a continuous layer of asbestos fabric, magneso calcite or other fire-resisting material approved by the commissioner. The tops of all heating furnaces and smoke pipes shall be at least one foot below the nearest wooden beams or ceiling. All ceilings imme- diately over a furnace or boiler, and for six feet on each side thereof, and all ceilings over indirect radiators shall, except under fireproof floors, be metal lathed and plastered. All hot-air register boxes in the floors or partitions of buildings shall be set in soapstone or equally fireproof borders not less than two inches in width, shall be made of tin plate, and shall have double pipes and boxes properly fitted to the soapstone. Hot-air pipes and register boxes shall be at least one inch from any woodwork, and register boxes shall be fifteen inches by twenty-five inches, or larger, and their con- necting pipes shall be two inches from any woodwork. If indirect hot water or indirect steam heat is used, the commissioner may modify or dispense with the foregoing requirements. Fireproof Partitions. SECT. 33. Partitions in buildings of first class construction shall be constructed of plastering applied to metal lathing, or to plaster boards. 24 . Acts of 1907, Chapter 550. or to hollow blocks composed of cement, plaster, or terra-cotta. When block construction is used it shall be self-supporting above all openings, thoroughly bonded and set in Portland cement. The blocks shall start from the floor and shall be continuous to the floor above, except that in the upper story, where there is a space between the ceiling of the top story and the roof, these partitions need not extend above the ceiling. If plastered on both sides the blocks shall be not less than four inches thick up to a height of fifteen feet, and shall be increased one inch for every additional eight feet or fraction thereof. The thickness of webs shall be not less than three fourths of an inch. If partitions are not plastered on both sides, the thickness of blocks shall be one inch greater than as specified above. Timbers in Walls of Second Class Buildings. SECT. 34. The ends of all wooden floor or roof beams in second class buildings shall enter the wall to a depth of at least four inches. When the wall is eight inches thick it shall be corbelled or the beams shall be hung in metal hangers; and the ends of all such beams shall so be shaped or arranged that in case of fire they may fall without injury to the wall. Alteration of Existing Buildings. SECT. 35. Any building, except those of third class construction within the building limits, having not more than five floors above the mean grade of all the sidewalks, may be altered, remodelled or enlarged for use as a house for habitation using second class construction. The first story or basement, or both the first story and basement, in such buildings may be used for mercantile purposes, provided that the walls and ceilings surrounding the area so used shall be fire-stopped to the satisfaction of the commissioner. The height of any such building shall not be increased unless the walls and foundations conform to the provisions of this act. The number of stories of such a building shall not exceed five above the cellar or base- ment. Every such building, more than thirty-three feet in height, so altered, remodelled or enlarged, shall be provided with at least two independent exits satisfactory to the commissioner. Every such building, so altered, remodelled or enlarged, shall have, in addition to the exposure on the widest street, an exposure as long as the average width of the building, upon a space open from the ground to the sky, at least ten feet wide for the first three stories, and increasing in width five feet for the next two stories. If the proposed building is more than five stories in height, said space shall be twenty feet : provided, that if the basement and first story are adapted or enlarged for use for mer- cantile purposes, the exposure required by this section shall not apply to that part of the building; and provided, also, that sufficient space be retained on the lot for the storage of ashes and garbage. Such exposure may be either upon private or public ways, or upon land which is dedicated for the use of the building, and may be divided and placed as approved by the building commissioner. These spaces shall remain undiminished so long as the building is used for habitation. Acts of 1907, Chapter 550. 25 If the building is situated on the corner of streets or private ways not less than ten feet wide the commissioner may approve the omission of the whole or part of this additional exposure. If in the opinion of the commissioner the alteration proposed to be made in a building is of such extent as, when done, to produce a practi- cally new structure or to impair the stability or increase the fire risk of the structure as a whole, then the whole structure shall be made to con- form to the provisions of this act for a new structure of the same class. A building damaged by fire or other casualty may be repaired or restored so as to conform to its original condition, or may be reconstructed in some or all of its parts, so as to conform to the requirements of this act for new buildings, as the commissioner may specify in his permit. Every living room in a building adapted for habitation shall have a window on the open air of an area not less than ten square feet and dis- tant in a three story building not less than six feet from any opposite wall; distant in a four story building not less than eight feet from any opposite wall ; distant in a five story building not less than ten feet from any opposite wall. This shall not apply to the construction of third class buildings, except the provision for a window on the open air of an area. The exposure required under this section shall apply to all buildings hereafter constructed adapted for habitation, except as is otherwise pro- vided for tenement houses. Floors Loads. SECT. 36. All new or renewed floors and stairs shall be so con- structed as to carry safely the weight to which the proposed use of the building may subject them, and every permit granted shall state for what purpose the building is designed to be used; but the least capacity per superficial square foot, exclusive of materials, shall be: For floors of houses for habitation, fifty pounds. For office floors and for public rooms of hotels and houses exceeding five hundred square feet, one hundred pounds. For floors of retail stores and public buildings, except schoolhouses, or for light manufacturing, one hundred and twenty-five pounds. For floors of schoolhouses, other than floors of assembly rooms, sixty pounds, and for floors of assembly rooms, one hundred and twenty-five pounds. For floors of drill rooms, dance halls and riding schools, two hundred pounds. For floors of warehouses and mercantile buildings, at least two hun- dred and fifty pounds. For flat roofs, forty pounds. For stairs, landings, platforms and fire escapes, seventy pounds. The loads not included in this classification shall be determined by the commissioner. The full floor load specified in this section shall be included in pro- portioning all parts of buildings designed for warehouses, or for heavy mercantile and manufacturing purposes. In other buildings, however, reductions may be allowed, as follows: for girders carrying more than one hundred square feet of floor, the live load may be reduced ten per cent. For columns, piers, walls and other parts carrying two floors, a Deduction of fifteen per cent of the total live load may be made; where 26 Acts of 1907, Chapter 550. three floors are carried, the total live load may be reduced by twenty per cent; four floors, twenty-five per cent; five floors, thirty per cent; six floors, thirty-five per cent; seven floors, forty per cent; eight floors, forty-five per cent; nine or more floors, fifty per cent. The commissioner may prescribe the maximum loads which may be imposed upon the floors of existing buildings. Shutters. SECT. 37. In all first or second class mercantile or manufacturing buildings over thirty feet in height, outside openings in party walls, or in any rear or side wall within twenty feet of an opposite wall or building, shall have metal frames and sashes and shall be glazed with wire glass or shall be protected by shutters. Such shutters shall be covered on both sides with tin or shall be made of other substantial fireproof material, and hung on the outside, either upon independent metal frames or upon metal hinges attached to the masonry, and shall be made to be handled from the outside, and one such shutter in each room shall have a protected hand-hole eight inches in diameter. Elevators. SECT. 38. Elevators and hoists for freight which do not run above the first story may be constructed without fireproof enclosures. Freight and passenger elevators may be placed in areas or hallways where the same are continuous and unbroken, such elevators to be protected by metal grille. Except as above provided, all shafts for elevators, hoists, dumb-waiters, lifts, light and ventilating shafts or other air ducts shall be constructed of fireproof material. The tops of all such shafts shall be covered with fireproof material unless the shaft extends above the upper floor of the building, and in that case the shaft shall be carried at least three feet above the roof and shall be covered with a skylight. Such shafts, if for freight or passenger elevators, shall be of brick at least eight inches thick, or of metal covered on both sides with at least one inch of plaster applied immediately to the metal, or with some other equally substantial fireproof material. Every opening into a shaft or hoistway shall be protected by self- closing gates, rails, trap-doors, or other equivalent devices. Every elevator shall be provided with a safety attachment to prevent the falling of the car. The machinery over the elevator shall have under- neath it a grille sufficient to protect the car from falling material. Every opening into an elevator shaft or hoistway and every opening through a floor, other than a stairway, shall be closed when not in use. All elevator shaft openings, other than openings into passenger ele- vator shafts, shall be furnished with metal-covered or incombustible doors, hung in a manner satisfactory to the commissioner, and shall be provided with iron thresholds. Wire glass panels may be used in such doors. Outside windows or openings of every elevator shaft shall have three vertical iron rods, painted red, equally spaced off in such window or opening. Freight elevators shall be equipped with a suitable danger signal to warn people of the approach of the elevator. The space between the car and door of each landing shall be not more than two inches. Acts of 1907, Chapter 550. 27 No elevator shall be used in any building until the same is approved in writing by the commissioner. In case any freight or passenger elevator is not constructed or fur- nished in compliance with this act, or has become unsafe, the com- missioner shall post a conspicuous warning and prohibition at each entrance to such elevator. It shall thereafter, until a new written permit is given by the commissioner, be a penal offence hereunder to operate the said elevator, or to remove or deface the said notice. Freight elevator wells hereafter built on the line of the external wall of a building shall be so constructed that there shall be no recess in the outer wall along the whole line of the same, and that no more than four inches space shall be allowed between the platform of the car and the outer wall. The side of the platform and the line of the doorway shall be flush with the well-way, and the door openings from the said elevator well into the building shall be placed at least six inches back from the face of the well, so as to allow space enough for self-closing gates to operate between the door and the well opening. Outside openings to freight elevators shall be protected by self-closing slatted gates, " ver- tical ", with spaces not wider than two inches between the slats. All elevators running at a speed of more than one hundred feet a minute, shall be operated by competent persons not less than eighteen years of age, and no other person shall operate or have the care or charge of such an elevator. No elevator shall be operated by or placed in charge of any person under sixteen years of age. No elevator shall hereafter be installed in any building without a permit having been granted therefor, and the applicant shall submit a plan showing the proposed location of the shaftway, the area and situ- ation of the machine room, and the said plan shall be filed as part of the records of the department. All elevators hereafter installed shall be located so as to give easy and safe access to all the principal parts of the machinery for inspection and repairs. All passenger elevators hereafter built operated by drum and cables, shall have an overspeed governor to prevent the car from descending at overspeed, and all passenger and freight elevators shall have a slack cable device to stop the machinery in case the car is held up or the cables part. If any accident shall occur to any elevator affecting life or limb or damaging any part of the machinery or running parts of the elevator, it shall be the duty of the engineer or superintendent in charge imme- diately, before any repairs are made, or any broken pieces are removed, to notify the commissioner of the accident, before the elevator is operated again, so that the cause of the accident may be determined, any faulty construction remedied, and satisfactory repairs made. All elevator cables hereafter installed that pass through bevelled sockets, the ends returning and refitting into the same, shall have in addition lead or babbitt metal poured into the ends of the socket, to prevent the possibility of the cable's slipping. All manufacturers of elevators shall be required to test, in the pres- ence of an inspector, the safety devices of every elevator installed before the same is turned over to the owners for use, and the commissioner shall be notified by the manufacturer at least twenty-four hours before 28 Acts of 1907, Chapter 550. such test is made. An inspector may require a test of the safety device of any elevator if in his judgment the same is required. The commissioner may require additional safeguards on elevators, if in his judgment the condition, use or surroundings of the elevator demand them. The commissioner may, with the approval of the mayor, appoint com- petent elevator inspectors in addition to those already detailed, one for every one thousand elevators and hoistways in the city of Boston. Wooden Buildings. SECT. 39. Every wooden building hereafter erected shall have a foundation of concrete, rubble, block granite or brick, laid in mortar or other equally substantial material, carried to the surface of the ground. Every such foundation if of brick or concrete, shall be at least twelve inches thick; if of granite, shall be at least sixteen inches thick; if of rubble, shall be at least twenty inches thick; and shall be laid at least four feet below any surface exposed to frost and upon solid ground or upon piles properly spaced. Every wooden building hereafter erected or altered, the sills of which do not rest directly upon a foundation as above described, but on an underpinning, shall have such underpinning made of brick, stone or concrete; and if the building is thirty-three feet or less in height above the highest street level of its principal front, the underpinning, if of brick or concrete, shall be at least eight inches thick, and if the building is of greater height, the underpinning, if of brick or concrete, shall be at least twelve inches thick; every underpinning of stone shall be at least sixteen inches thick. Every wooden building, hereafter erected on soft and marshy land, and used for a workshop or other like purpose, or as a temporary structure, may, if the commissioner approves, rest upon mud sills or blocks, or on piles. Every wooden building hereafter erected or altered shall have all its parts of sufficient strength to carry the weight of the superstructure; shall be built with sills, posts, girts, studs and plates, properly framed, mortised, tenoned, braced and pinned in each story, or with a balloon frame; the posts and girts shall be not less than four by six inches in cross section, and the studs shall be not more than twenty inches apart. Wooden buildings hereafter erected for other purposes than habitation shall not be situated within five feet of the line of the lot unless the side wall on such line or lines be of brick or concrete, built to the under side of the roof. SECT. 40. No wooden building hereafter erected to be used as a habitation shall be more than three stories in height above the basement, nor more than forty-five feet in height above the street level, nor shall any part of such building, except the eaves and cornice, be nearer than three feet to the line of any adjoining lot, and if built on land of the same owner, nearer than six feet to any other building, unless the side wall of such adjoining building is constructed as a solid brick or concrete wall not less than eight inches thick and carried twelve inches above the roof. Every wooden building hereafter constructed to form a block of two or more houses shall have a brick or concrete party wall between adjoin- ing houses, which shall be not less than eight inches thick, shall be Acts- of 1907, Chapter 550. 29 carried twelve inches above the roof, and shall be capped with a metallic covering. Flooring during Construction. SECT. 41. If, in the erection of an iron or steel frame building, the spaces between the girders or floor beams of a floor are not filled and covered by the permanent construction of such floors before another story is added to the building, a close plank flooring shall be placed and maintained over such spaces during construction. If and when such flooring cannot be used without serious interference with the work of construction, such provision shall be made to protect the workmen from falling materials as will be satisfactory to the commissioner. ADDITIONAL REQUIREMENTS FOR TENEMENT HOUSES. Definitions. SECT. 42. Certain words are defined as follows: (1.) A tenement house is any house, building, structure or portion thereof, occupied, or adapted for occupation, as a dwelling by more than three families living independently of one another and doing their cook- ing upon the premises, or by more than two families above the first story so living and cooking. A family living in a tenement house may consist of one or more persons. An existing tenement house is any building erected as such or con- verted to such use or as altered for such use or so used before the passage of this act, and any building adapted for such use, provided that a permit was issued for the erection of said building before the passage of this act. A tenement house hereafter erected is any tenement house other than an existing tenement house as above defined. (2.) A corner lot is a lot situated at the junction of two or more streets, or of two or more streets and alleys or open passageways not less than fifteen feet in width. (3.) A yard is an open unoccupied space on the same lot with a build- ing and between the extreme rear line of said building and the rear line of the lot. (4.) A court is an open unoccupied space other than a yard on the same lot with a building. An inner court is a court not extending to a street, or alley, or open passageway, or yard. An outer court is a court extending to a street, or alley, or open passageway, or yard. A vent court is an inner court for the lighting and ventilation of water-closets, bathrooms, public halls, and stair halls only. An intake is a passageway connecting an inner court with a street, or alley, or open passageway, or yard. (5.) A shaft, whether for air, light, elevator, dumb-waiter, or any other purpose, is an enclosed space within a building, extending to the roof, and covered either by a skylight or by the roof. A vent shaft is a shaft used solely to ventilate or light water-closet compartments or bathrooms. (6.) A. public hall is a hall, corridor, or passageway not within an apartment. (7.) A stair hall includes the stairs, stair landings, and those parts of 30 Acts of 1907, Chapter 550. the public hall through which it is necessary to pass in going from the entrance floor to the roof. (8.) An apartment is a room, or suite of two or more rooms, occupied or suitable for occupation, as a residence for one family. (9.) Repairs means any renewal of any existing part of a building, or of its fixtures or appurtenances, which does not lessen the strength of the building. Fire-escapes. SECT. 43. In all tenement houses hereafter erected and more than three stories in height above the basement or cellar there shall be pro- vided one of the following means of egress for escape from fire: (1) an interior enclosed stairway as described in this section; or (2) an exterior iron fire-escape and stairs as hereinafter described; or (3) iron balconies connecting with adjoining houses, or with adjoining parts of the same house separated from each other by a brick partition wall in which there are no openings except such as are protected with fireproof self-closing doors; and every apartment above the first floor shall have access to one of such means of egress. (1.) Interior fire-escapes may consist of wooden circular stairs, occu- pying a space of a diameter not less than four feet six inches. Such stairs shall extend from the top floor to the level of the basement, where they shall open into either an outer or an inner court or yard. These stairs shall be separated in the basement from the basement by brick walls at least eight inches thick, and the stairs above the basement shall be enclosed with fireproof partitions clear to a vent skylight, and shall have on each floor, in a public hall accessible from each apartment, a fireproof self-closing door and fireproof frame; the door to open into the corridor, and to be so arranged that it cannot be opened from the stair side; such staircase to be provided with a ventilating skylight at least nine square feet in area. The soffits of the stairs, if they are of wood, shall be plastered on metal lathing. (2.) Exterior fire-escapes shall be of iron, with iron grated floor, and capable of bearing a load of seventy pounds per square foot. The stair treads shall be of iron, and the pitch of the stairs shall not exceed sixty degrees. Balconies shall be at least three feet four inches wide, and the stairs at least twenty inches. There shall be a landing at the foot of each flight, and at the level of the second floor there shall be cantilever lad- ders. The rails on horizontal balconies and on the stairs shall be at least two feet ten inches high at all points. (3.) Balconies connecting adjoining houses, or adjoining parts of the same house as described above, shall be not less than thirty inches wide and capable of sustaining a load of seventy pounds per square foot. Railings shall be not less than two feet ten inches high, and shall be of iron. Bulkheads and Scuttles. SECT. 44. Every tenement house of the first or second class here- after erected shall have in the roof a fireproof bulkhead with a fireproof door to the same, and shall have fireproof stairs with a guide or hand rail leading to the roof, except that in such tenement houses which do not Acts of 1907, Chapter 550. 31 exceed sixty-five feet in height, such bulkheads may be of wood covered with metal on the outside and plastered on metal lathing on the inside; provided that the door shall be covered with metal on both sides. Every other tenement house shall have in the roof a bulkhead or scuttle. No scuttle shall be less in size than two feet by three feet, and all scuttles shall be covered on the outside with metal, and shall be pro- vided with stairs or stationary ladders leading thereto and easily accessi- ble to all tenants of the building, and kept free from encumbrance, and all scuttles and ladders shall be kept so as to be ready for use at all times. No scuttle shall be situated in a closet or room, but all scuttles shall be in the ceiling of the public hall on the top floor, and access through the scuttle to the roof shall be direct and uninterrupted. Scuttles shall be hinged so as to readily open. Every bulkhead hereafter constructed in a tenement house shall be constructed as provided for tenement houses hereafter erected and shall have stairs with a guide or hand rail leading to the roof, and such stairs shall be kept free from encumbrance at all times. No lock shall be placed on any scuttle or bulkhead door, but either may be fastened on the inside by movable bolts or hooks. All key-locks on scuttles and on bulkhead doors shall be removed. No stair- way leading to the roof in a tenement house shall be removed. Stairs and Public Halls. SECT. 45. Every tenement house hereafter erected shall have at least one stairway extending from the entrance floor to the roof, and every tenement house hereafter erected containing more than one hun- dred rooms above the first floor, exclusive of water-closets and bath- rooms, shall have an additional separate stairway for every additional one hundred rooms or fraction thereof. Public halls therein shall each be at least three feet wide in the clear, and stairs shall be at least three feet wide between the wall and the stair rail. Each stairway shall have an entrance on the entrance floor from a street or alley or open passageway or from an outer court, or from an inner court which connects directly with a street or alley or open passage- way. All stairs shall be constructed with a rise of not more than eight inches, and with treads not less than nine inches wide and not less than three feet long in the clear. Where winders are used all treads at a point eighteen inches from the strings on the wall side shall be at least ten inches wide. In every tenement house all stairways shall be provided with proper balusters and railings kept in good repair. No public hall or stairs in a tenement house shall be reduced in width so as to be less than the minimum width prescribed in this section. Stair Halls, Construction of. SECT. 46. In tenement houses hereafter erected which do not exceed five stories above the cellar or basement or sixty-five feet in height the stair halls shall either be constructed with iron beams and fireproof filling or shall be filled in between the floor beams with at least five inches of cement deafening. In such houses the stairs may be of wood, provided that the soffits are covered with metal laths and plastered with two coats of mortar, or with good quality plaster-boards not less 32 Acts of 1907, Chapter 550. than one half inch in thickness made of plaster and strong fibre, and all joints made true and well pointed, and provided that such stairs are furnished with firestops. Stair Halls, how Enclosed. SECT. 47. In second class and third class tenement houses here- after erected, the stair halls may be enclosed with wooden stud parti- tions, if such partitions are covered on both sides with metal laths or with good quality plaster-boards not less than one half inch in thickness, made of plaster and strong fibre, and all joints made true and well pointed, and provided that the space between the studs is filled in with brick and mortar or 'other incombustible material to the height of the floor beams. Entrance Halls. SECT. 48. Every entrance hall in every tenement house hereafter erected shall be at least three feet six inches wide in the clear, from the entrance up to and including the stair enclosure, and beyond this point at least three feet wide in the clear, and shall comply with all the condi- tions of the preceding sections of this act as to the construction of stair halls, except that in a fireproof tenement, house hereafter erected the entrance hall may be enclosed with terra-cotta blocks not less than four inches thick and angle-iron construction, instead of brick walls. If such entrance hall is the only entrance to more than one stairway, that portion of said hall between the entrance and the stairway shal be increased at least eighteen inches in width in every part for each additional stairway. Cellar Ceilings. SECT. 49. In all tenement houses of the second or third class hereafter erected, the cellar and basement ceilings shall be lathed with metal laths and plastered. Partitions, Construction of. SECT. 50. In all tenement houses of the second or third class here- after erected all stud partitions which rest directly over each other shall run through the wooden floor beams and rest upon the cap of the parti- tion below, and shall have the studding filled in solid between the up- rights to the depth of the floor beams with suitable materials. Wooden Tenement Houses. SECT. 51. Outside of the building limits, tenement houses not ex- ceeding three stories in height above the basement, nor eighteen hundred square feet in area, may be erected of wood. No wooden tenement house shall be increased in height so as to exceed three stories above the basement or cellar. Shafts. SECT. 52. All elevator or "dumb-waiter shafts hereafter constructed in any tenement house' shall be fireproof throughout, with fireproof self- closing doors at all openings at each story. But nothing in this section Acts of 1907, Chapter 550. 33 shall be so construed as to require enclosures about elevators or dumb- waiters in the well-hole of stairs where the stairs themselves are enclosed in walls of incombustible materials, and are entirely constructed of fire- proof materials as hereinbefore provided. Every vent shaft hereafter constructed in any tenement house shall have an intake of at least the dimensions provided for vent courts in section sixty-one, and shall be of the same minimum dimensions; and the skylight covering such vent shaft shall be raised at all points at least one foot above the top of the walls of such vent shaft, and the space between the top of said walls and the skylight shall remain at all points open and unobstructed except for such supports essential to the stability of the skylight, as may be approved by the commissioner. Bakeries and Fat Boiling. SECT. 53. No bakery and no place of business in which fat is boiled shall be maintained in any tenement house which is not fireproof through- out, unless the ceiling and side walls of said bakery or of the said place where fat boiling is done are made safe by fireproof materials around the same, and there shall be no openings either by door or window, dumb- waiter shafts or otherwise, between said bakery or said place where fat is boiled in any tenement house and the other parts of the building. Other Dangerous Businesses. SECT. 54. All transoms and windows opening into halls from any part of a tenement house where paint, oil, spirituous liquors or drugs are stored for the purpose of sale or otherwise shall be glazed with wire- glass, or they shall be removed and closed up as solidly as the rest of the wall. There shall be between any such hall and such part of said tene- ment house a fireproof self-closing door. LIGHT AND VENTILATION. Yards. SECT. 55. The requirements for yards hereinafter provided shall be deemed sufficient for all tenement houses. Except in those cases hereinafter provided for, there shall be, behind every tenement house hereafter erected, a yard extending across the entire width of the lot, and at every point open from the ground to the sky unobstructed, except by fire-escapes or unenclosed outside stairs. The depth of said yard shall be measured from the extreme rear wall of the house to the rear line of the lot, and at right angles to said line, except that where there is an alley or open passageway in the rear of the lot the depth of the yard may be measured to the middle of said alley or open passageway. On an irregular lot of several depths, where there is more than one rear line to the lot, such yard may extend across the entire width of the lot in sections, provided that each section of the yard is in every part and at every point of the minimum depth hereinafter pre- scribed. Where the side lines of a lot converge toward the rear, the depth of the yard shall be such as to give it an area equal to the greatest width of the yard multiplied by the depth hereinafter prescribed. Except on a corner lot, the depth of the yard behind every tenerre.it 34 Acts of 1907, Chapter 550. house hereafter erected fifty feet in height or less shall be not less than twelve feet in every part. All yards without exception shall be increased in depth at least one foot for every additional ten feet of height of the building, or fraction thereof, above fifty feet. Except as hereinafter otherwise provided, the depth of the yard behind every tenement house hereafter erected upon a corner lot shall not be less than six feet in every part. But where such corner lot is more than twenty-five feet in width, the depth of the yard for that portion in excess of twenty-five feet shall be not less than twelve feet in every part, and shall increase in depth as above provided. Whenever a tenement house is hereafter erected upon a lot which runs through from street to street, or from a street to an alley or open passage- way, and said lot is one hundred and fifty feet or more in depth, said yard space shall be left midway between the two streets, and shall extend across the entire width of the lot, and shall be not less than twenty-four feet in depth from wall to wall, and shall be increased in depth at least two feet for every additional ten feet in height of the building, or fraction thereof, above fifty feet. When a tenement house hereafter erected does not front upon a street, a public alley, or a passageway, not less than fifteen feet wide, the re- quirements in this section as to yards shall apply to the front of such tenement house as well as to the rear. Neither the yard behind one tenement house nor any part thereof shall be deemed to satisfy in whole or in part the requirement of a yard in front of another tenement house. Cases in which no Yard shall be required. SECT. 56. No yard shall be required behind a tenement house hereafter erected upon a lot which abuts at the rear upon a railroad right of way, a cemetery or a public park. No yard shall be required behind a tenement house hereafter erected upon a lot entirely surrounded by streets or by streets, alleys or open passageways, not less than fifteen feet in width, or by such streets, alleys, and passageways and a railroad right of way, a cemetery or a public park. No yard shall be required behind a tenement house hereafter erected upon a lot less than one hundred and fifty feet deep and running through from street to street or from a street to an alley or open passageway not less than fifteen feet in width, or upon a corner lot adjoining a lot less than one hundred and fifty feet deep and running through from street to street, or from a street to such an alley or open passageway. No yard shall be required behind a tenement house hereafter erected upon a corner lot adjoining a lot more than one hundred and fifty feet deep and running through from street to street or from a street to an alley or open passageway not less than fifteen feet in width; but if there be no yard, an outer court upon such corner lot shall extend from the street along the line of such adjoining lot to a point in line with the middle line of the block; the width of said court to be not less than the width of court prescribed in the ensuing paragraph. No yard shall be required behind a tenement house hereafter erected upon a corner lot adjoining two or more lots any one of which bounds upon a single street, or alley, or open passageway not less than fifteen feet in width; but if there be no yard an outer court upon such corner lot shall extend from the street, or from such alley or open passageway Acts of 1907, Chapter 550. 35 along a lot line either to the extreme rear of an adjoining lot or to the extreme rear of said corner lot: provided, that the width of said court measured from the lot line to the opposite wall of the building, for tene- ment houses fifty feet or less in height, shall be not less than six feet in every part, and for every additional ten feet of height of the tenement house shall be increased one foot throughout t>he whole length of said court. Courts. SECT. 57. No court of a tenement house hereafter erected shall be covered by a roof or skylight, but every such court shall be at every point open to the sky unobstructed. Except such courts as are pro- vided for in section fifty-six, all courts, except for fire-escapes, may start at the second tier of beams. Outer Courts. SECT. 58. The provisions of this section shall apply only to tene- ment houses hereafter erected. Where one side of an outer court is located on the lot line, the width of the said court, measured from the lot line to the opposite wall of the building, for tenement houses fifty feet or less in height shall not be less than six feet in every part; and for every ten feet of increase or fraction thereof in height of such tenement houses, such width shall be increased one foot throughout the whole length of the court, and except where the court runs through from the yard to the street, said width shall never be less than one eighth of the length of the court. Where an outer court is located between wings or parts of the same building, or between different buildings on the same lot, the width of the court, measured from wall to wall, for tenement houses fifty feet or less in height shall not be less than twelve feet in every part, and for every ten feet of increase or fraction thereof in the height of the said building, such width shall be increased two feet throughout the whole length of the court. The depth of such courts shall never exceed four times their width. Wherever an outer court changes its initial horizontal direction, or wherever any part of such court extends in a direction so as not to receive direct light from the street or yard, or from an alley, or open passageway not less than fifteen feet in width, the length of that part of the court shall never exceed its width, such length to be measured from the point at which the change of direction begins. Wherever an outer court be- tween parts of the same building is twelve feet or less in depth, its width may be one half its depth, provided that such width is never less than four feet in the clear. This exception shall also apply to every offset or recess in outer courts. And no window except windows of water-closet compartments, bathrooms, or halls shall open upon any offset or recess less than four feet in width. Inner Courts. SECT. 59. The provisions of this section shall apply only to tene- ment houses hereafter erected. Where one side of an inner court is located on the lot line and the building does nr>f ^YPPPH fiff,y feet in height, the least width of the court shall be not lesd (than eight feel, ttu