the fireproof floor arches, on concrete, or on brick; and all other partitions shall be wedged tightly between the floor and the ceiling with incombustible wedges.

369. COVERING OF SPANDREL BEAMS, GIRDERS AND LINTELS.] The metal of the exterior side of the spandrel beams, girders, or lintels of exterior walls shall be covered in the same manner and with the same material as specified for the external columns in this Act, provided shelf angles connected to girders by brackets, or projections of girder flanges not figured as part of the flange section, may come within 2 inches of the face of the brick or other covering of such spandrel beams, girders, or lintels. The covering thickness shall be measured from the extreme projection of the metal in every case.

370. COVERING OF BEAMS, GIRDERS, AND TRUSSES.] (a) The metal beams, girders, and trusses of the internal structural parts of a building shall be covered by one of the fireproof materials herein specified, so applied as to be supported entirely by the beam or girder protected.

(b) If the covering is of brick, it shall be not less than 4 inches thick. If the covering is of hollow tile, or if of solid porous tile, or if of terra cotta, such tile shall be not less than 2 inches thick, and shall be set in a bed of cement mortar. If hollow tile is used, it shall have such a form that there shall be an air space of at least three fourths of an inch thick within such clay covering. If the covering is of concrete, its minimum thickness on the bottom and sides of the metal shall be 2 inches.

(c) The top of all beams, girders, and trusses shall be protected by not less than 2 inches of concrete, or by 1 inch of burnt clay bedded solid on the metal in cement mortar.

(d) In all cases of beams, girders, or trusses in roofs or floors, the protection of the bottom flanges of the beams and girders and so much of the same as is not covered by the arches, shall be made as herein specified for the covering of beams and girders. In every case the thickness of the covering shall be measured from the extreme projection of the metal, and the entire space or spaces between the covering and the metal, excepting the air spaces in the hollow tile, shall be filled completely with one of the fireproof materials.

(e) All girders or trusses which support loads from more than one story shall be fireproofed with two thicknesses of fireproof material or a combination of two fireproof materials as required for external columns in section 371 of this Act, and each covering of fireproof material shall be bedded in cement mortar.

371. FIREPROOFING OF EXTERIOR COLUMNS.] (a) All iron or steel used as vertical supporting members of the external construction of any building exceeding 50 feet in height, shall be protected against the effects of external change of temperature, and of fire by a covering of fireproof material consisting of at least 4 inches of brick, hollow terra cotta, concrete, burnt clay tile, or of a combination of any two of these materials, provided their combined thickness is not less than 4 inches. The distance of the extreme projection of the metal, where such metal projects beyond the face of the column, shall not be less than 2 inches from the face of the fireproofing; provided, the inner side of the exterior columns shall be fireproofed as hereafter required for interior columns.

(b) Where stone or other incombustible material not of the type defined in this Act as fireproof material, is used for the exterior facing of the building, the distance between the back of the facing and the extreme projection of the metal of the column proper shall be at least 2 inches, and the intervening space shall be filled with fireproof materials.

(c) In all cases the brick, burnt-clay tile, or terra cotta, if used as a fireproof covering, shall be bedded in cement mortar close to the iron or steel members, and all joints shall be made full and solid.

372. FIREPROOFING OF INTERIOR COLUMNS.] (a) Covering of interior columns shall consist of one or more of the fireproof materials herein described.

(b) If such covering is of brick or concrete, it shall not be less than 4 inches thick. If of hollow or porous burnt-clay tile, such covering shall be in two consecutive layers, each not less than 2 inches thick, each having one air space of not less than one half inch; and in no hollow burnt-clay tile shall the burnt clay be less than five-eighths of an inch thick. If con

stituted of a combination of any two of these materials, one half of the total thickness required for each shall be applied.

(c) In the case of columns having an "H" shaped cross section or of columns having any other cross section with channels or spaces open from base plates to cap plates on one or more sides of the column, then the minimum thickness of the fireproof covering may be reduced to not less than 2 inches, measured in the direction in which the flange or flanges project, provided the thin edge in the projecting flange or arms of the cross sections does not exceed three quarters of an inch in thickness. The thickness of the fireproof covering on all surfaces measuring more than three quarters of an inch wide, in a direction perpendicular to such surface, shall not be less than that specified for interior columns in the beginning of this section; and all spaces, including those between the fireproof covering and the metal of the columns, shall be filled with fireproof material. Lattice or other open columns shall be completely filled with approved cement concrete.

(d) Burnt clay-tile column-covering shall be secured by winding wir? around the column after all the tile has been set around such columns. The wire shall be securely wound around tile in such manner that every tile is crossed at least once by a wire. If iron or steel wire is used, it shall be galvanized; and no wire used shall be less than No. 12 gage.

(e) In places where there is trucking or wheeling, or handling of packages of any kind, the lower five feet of every column encased with hollow tile shall be protected by a covering of No. 16 U. S. gage steel embedded in concrete.

373. TIME OF PLACING FIREPROOF COVERING.] The fireproof covering of the steel structural-members shall be applied previous to, and independently of, the placing of the architectural facing.

374. SEGMENTAL AND FLAT ARCHES.] (a) The least thickness of a hollow tile or porous terra-cotta segmental or flat floor arch shall be one half of an inch per foot of span; but no such hollow-tile or terra-cotta arch shall be of thickness less than 5 inches.

(b) Both flat and segmental arches shall be so constructed that the joints of the same radiate from a common center; and there shall be a cross rib in each tile block for every 4 inches or fractional part thereof in height. The skew back of the arches shall be carefully fitted to the beams supporting them; and in addition to the cross ribs, there shall be additional diagonal reinforcing ribs in the skew back. Such arches, whether flat or curved, shall have their beds well filled with cement mortar; and the centers shall not be struck until the mortar has set.

(c) Skew backs shall be molded in such a manner as to support the burnt-clay covering on the under sides of beams or girders.

(d) Segmental arches shall have a rise of at least one inch for each foot of span.

375. COVERING OF MULLIONS AND TRANSOM BARS.] In buildings required by this Act to be fireproof construction, on exposures where metal frames, doors, sash and wired glass are not required, all vertical door or window mullions over 8 inches wide shall be faced with incombustible material, and all horizontal transom bars over 6 inches wide shall be faced with a fireproof or an incombustible material.

376. Cut-out BOXES, CHASES, ETC.] No electric service cut-out box, switch box, cabinet, chase or any other recess shall encroach on the minimum thickness required for any fireproof covering on structural metal, except as provided in this Act. If the depth of any cut-out box, switch box, cabinet, chase or any other recess shall be concealed or partially concealed, then the thickness of the fireproof covering shall be increased correspondingly.

377. COURTS, AND LIGHT AND VENT SHAFTS.] (a) Every court or light or vent shaft of every fireproof building shall be open and unobstructed from the bottom of such court to the sky, with the exception that fire escapes may be built therein. Such courts or shafts shall have walls constructed in the same manner as required for the exterior walls of such buildings, provided no walls enclosing such courts are required on street or alley lot-line.

(b) All openings in court or shaft walls, except as otherwise provided in this Act, shall have metal frames, metal sashes and metal doors, with the glazed portion thereof of wired glass.

(c) The walls of every vent shaft of every masonry constructed building, except buildings of Class IIIc, shall be built of masonry or fireproof material not less than 4 inches in thickness, supported at each story by iron or steel construction.

378. BAY WINDOWS.] The walls of every bay window and every court in every masonry building, except buildings of Class IIIc, outside of the legally established fire limits, shall be built of brick or other fireproof construction throughout as required for exterior walls.

379. OPENINGS IN EXTERIOR WALLS.] (a) Where the distance from door or window openings in any building, except as hereinafter provided, is less than 30 feet from the opposite side of the established alley line, or where the windows and doors of two or more areas of the same building which is required to be separated by dividing walls are on a court, or where any such window or door is distant less than 30 feet from another window or door of another such area, or where the door or window openings are within 15 feet of an inside lot-line, such openings shall be protected by a door, shutter or window constructed of incombustible material or of wood completely enclosed in sheet metal.

380. DOORS IN EXTERNAL WALLS.] At least one of the first or ground-floor doors must be a swinging door. This section shall not apply to frame buildings, nor to buildings outside of the legally established fire limits of cities, towns and villages, nor to buildings of Class V one story high, nor to buildings of Class III not more than two stories high, nor to store windows fronting on streets.

(b) Where hollow metal doors are used to meet the requirements of this section they shall be made of sheet steel not less than 20 U. S. gage in thickness. The stiles and rails shall be at least one and three fourths inches thick, and the panels at least one fourth inch thick. Panels shall be constructed of two thicknesses of metal separately by one fourth inch of asbestos or one fourth inch wired glass not exceeding 36 inches in either width or height. Doors of this type shall be equipped with heavy hardware, and shall close into rabbeted frames made of steel or formed in the masonry.

(c) Where wood-filled paneled doors are used to meet the requirements of this section they shall be made of non-resinous wood and be covered with sheet steel at least 26 U. S. gage in thickness. The wood filling in the stiles and rails shall be at least three fourths inch thick and be covered on both sides with asbestos and be incased in a metal covering. The panels shall be of wood not less than 1 inch thick, or of wired glass or asbestos not less than one fourth inch thick. Both sides of the metal covering shall be painted or otherwise treated to prevent corrosion. Doors of this type shall be equipped with heavy hardware, and close into rabbeted frames made of steel or formed in the masonry.

(d) Where wood-filled tin-clad doors not having depressed panels are used to meet the requirements of this section, they shall be made of at least two thicknesses of not less than thirteen-sixteenths inch seasoned nonresinous wood of good quality, free from sap, free from large or loose knots, tongued and grooved, dressed on both sides, and not exceeding 8 inches in width. One layer shall be vertical and the other horizontal. The layers shall be firmly fastened together by wrought-iron clinch nails driven flush and clinched so as to leave smooth surfaces. The wood work shall be completely covered by terne plate, a full size sheet of which shall be 14 by 20 inches and weigh not less than 113 pounds per box of 112 sheets. All joints shall be locked one half inch, and all joints except on the edges of the door shall be nailed under the seams. Vertical joints shall be double locked, and horizontal joints single locked. Nails used to fasten tin must be No. 13 gage, full barbed wire nails. Doors shall be equipped with heavy hardware, and close into rabbeted frames made of steel or formed in the masonry.

(e) In addition to the doors specified in this section any other type of construction having at least equivalent fire-resisting properties may be accepted under standards approved by the State Building Commissioner.

381. DOORS IN INTERIOR WALLS.] (a) Whenever doors are inserted in. dividing walls, or in walls between non-fireproof and fireproof buildings, or between parts of either of such buildings, they shall be made to comply with the following specifications, and shall be mounted on each side of the wall.

(b) Such doors may be either sliding doors or swinging doors, and shall be so constructed, installed and maintained that they can be easily opened or closed from either side at all times by any person, provided rolling steel shutters may be used when such openings are not used as exits.

(c) Every door shall be equipped with a device containing a fusible or other releasing arrangement of equal efficiency, approved by the local or State Building Commissioner. There shall be one of these releasing arrangements immediately above the door opening, and also one above the opening near the ceiling. Where the ceiling is less than three feet above the door opening, the last mentioned fusible link or releasing device may be omitted provided the doors are so arranged that the operation of any one of the thermostats or other releasing devices will result in the closing of all the doors on both sides of the wall. Fusible links or other approved substitutes shall be made so that they will fuse or operate when subject to a heat of 160 or 165 degrees Fahrenheit. If said doors are made of steel plates, the plates shall not be less than No. 12 U. S. gage, and shall have a continuous 2 by 2 by %-inch angle-iron frame extending all around the same; and said doors shall have 2 by 2 by 3-inch panel-bars, not exceeding twenty-four inches apart, riveted to the plate of the door with not less than 3%-inch rivets spaced four inches to six inches between centers. Parts of swinging doors shall be so constructed that when the doors are closed, they will be of strength equal to that of a single door; and shall be so arranged that they will operate automatically. All doors shall be hung on wall frames of 4 by 3 by %-inch angle-iron or by 4 by %-inch bar iron stiffened by 11⁄2 by 11⁄2 by 4-inch angles riveted on the back and fitting snugly to the wall. The frame shall be fastened together by 34-inch bolts extending through the wall, such bolts being not more than two feet apart. All doors shall be made to fit closely to the wall frame on all sides. Lintels of door openings shall be made of brick, iron or concrete.

(d) Swinging iron doors shall swing on three wrought-iron hinges made of 2 by %-inch bar iron, and shall be secured by at least three lever bars 11⁄2 by %-inch iron, working together and so arranged as to be operated from either side of the door.

(e) Sliding iron doors shall slide in channels at the top and bottom. The bottom channels shall be formed by two angles 22 by %-inch and 11⁄2 by 1/4-inch, respectively. The top channel shall be formed by two angles 2 by %inch and 12 by 4 inch. The channels shall be securely riveted or bolted through the wall frame; and where they extend beyond the wall frame, they shall be firmly bolted to the wall by expansion bolts. The track shall be without incline, and be composed of 12 by 2-inch iron securely riveted on the upper side of the angle-iron channel. Hangers shall be of the antifriction pattern, and shall be securely fastened to the door plate by at least four 12-inch bolts. The wheels shall be of cast iron 34 by 42 inches.

(f) Sills between iron doors shall be of 14-inch iron or steel with edges securely fastened to an angle iron at least 11⁄2 by 12 by 4-inch, on the inner side of the wall frame. Where adjoining floors are of concrete construction, sill plates may be omitted.

(g) Tin-clad doors may be used for doors in dividing walls, provided they are constructed as described in paragraph (d) of section 380.

(h) Swinging tin-clad doors shall have 21⁄2 by 1⁄2-inch wrought-iron hinges bolted to the doors with four %-inch bolts. Doors more than seven feet high shall be provided with three hinges, and have wrought-iron walleyes built into the wall or riveted to wall frame or bolted through the wall with 4-inch bolts. Such doors shall have at least three lever bars of 11⁄2 by %-inch iron, working together. The latch shall be placed so it can be operated from either side of the door, and be provided with proper keepers through the door and with a spring to insure latching. Catches shall be made of 21⁄2-inch wrought iron securely bolted to the wall or wall frame.

(i) Sliding tin-clad doors shall be made of 31⁄2 by %-inch rolled steel or round bars or round pipes of equal strength, securely bolted through the wall with 4-inch bolts. The track shall be inclined three fourths of an inch to the foot. Hangers shall be made of 31⁄2 by %-inch wrought iron attached by not less than 1-inch bolts. Wheels shall be made of malleable or wrought iron with not less than 11⁄2-inch bearings on the axle. Doors over six feet

wide shall have three hangers, and shall be provided with the necessary binders, chafing strips, bumpers, and bumper shoes.

(j) Sill plates between tin-clad doors shall be of 14-inch iron or steel riveted to a 31⁄2 by 5-inch iron angle-iron on each side of the wall. The angle irons shall be fastened together through the wall by 4-inch bolts spaced not to exceed eighteen inches apart, provided that where adjoining floors are of concrete sill plates may be omitted.

(k) Rolling steel doors used for the protection of openings in dividing walls shall be made of galvanized steel not less than No. 16 U. S. gage. The vertical edge of each door shall be restrained by steel guides attached to the wall, and have a bearing of not less than one and one half inches. One door shall be mounted at each face of the wall at each opening. Each door shall be hung on a steel barrel having a shaft, and shall be provided with one or more helical steel springs so proportioned as to permit of the manual operation of the curtain. The design shall be such that failure of the counterbalance springs shall not permit the curtain to drop below its proper closedposition. Satisfactory provision shall be made to prevent passage of flame or smoke around the barrel and over the upper edge of the curtain. Each opening shall be provided with a sill as specified in paragraph (j) above.

382. WINDOWS IN EXTERIOR WALLS.] (a) Where hollow metal sash and wired glass are used to fulfill the requirements of this section, the glazed portions of the sash shall be set with wired glass having a thickness of at least one-fourth inch. The wire mesh shall not be larger than seven-eighths inch, and the wire used for such mesh shall not be smaller than No. 24 U. S. gage. The plane of the wire mesh shall be practically midway between the two surfaces of the glass. The unsupported area of the glass in any one light shall not exceed 720 square inches, nor shall either dimension exceed 48 inches. The glass must be supported by the construction of the sash in which it is held, independently of the material used for waterproofing purposes. The frames shall be so designed that they may be securely fastened to the wall. The frames shall be made of not less than No. 24 U. S. gage galvanized steel; and the metal shall be soft enough to permit all necessary bending without the breaking of the metal or the scaling of the galvanizing. Frames and sash may also be made of not less than 20-ounce copper or other metal of equal strength and durability which will not melt at a lower temperature than copper. All parts of frame and sash shall be securely fastened together by interlocking seams, rivets, or clips. Grooves for receiving the glass shall be at least three fourths inch in depth, and the actual bearing of the glass shall be at least five eighths inch. The head of the frame shall be closed at the top, and the piece forming this closure shall be securely fastened to each side of the member. The sill shall be filled with concrete or other incombustible material. The stiles and the rails of sash shall be at least one and three fourths inches wide and thick, and the members shall be securely fastened together at each corner. The sash shall fit the frame closely when closed.

(b) Lifting or sliding sash shall be counter-weighed by weights in the jamb, or be so arranged that one sash shall counter-balance the other. When weights are used, they shall be properly separated by parting strips in the boxes; and shall be accessible through openings in the face of the jamb. Windows of these types shall be provided with metallic sash-chain or cable, and smooth running sash pulleys securely fastened in place. The sash chain or cable shall be of sufficient strength to withstand severe heat without parting, and be thoroughly protected against moisture and corrosion. The sash shall be fitted into the frame with suitable stops and parting beads of metal. The sash shall be removable. The meeting rails of the sash shall be so constructed that they will prevent excessive passage of flame. The sash shall be equipped with a substantial sash lock securely fastened in place.

(c) Horizontally pivoted sash shall be riveted above the center on steel pivots at least three eighths inch in diameter. The pivots shall work in brass-bushed eye-plates securely fastened to the window. Sash and frames shall be reinforced at the places where pivots and eye-plates are attached by riveting on one-eighth inch iron strips. Pivoted sash shall be provided with suitable stops and an effective attachment for holding them open or closed. The sash shall be provided with substantial gravity locks and catches at top and bottom, and such latching mechanism must be positive in action.