298. ASHLAR FACING.] Ashlar facing of masonry walls shall be considered as a part of the wall for the purpose of carrying weight, only when every second course extends into the backing a distance equal to the least thickness of ashlar facing. In addition to such bond every stone in all courses shall be tied to the backing by two galvanized iron anchors. No ashlar facing shall be less than 4 inches thick, nor shall the height of any stone exceed five times its thickness. 299. BRICK.] The brick used in any building shall be good, straight, hardburned brick. Soft brick may be used in any part of the building where they will not be exposed to the weather, but shall not be used in external or internal piers or bearing walls. When old bricks are used in any wall, only hard, well-burned brick shall be used. 300. BRICKWORK, BOND OF.] The bond of all brickwork shall be formed by laying one course of headers for every six courses of stretchers, provided in pressed-brick facing two headers and a stretcher may be laid alternately in every seventh course, or an equivalent number of full headers may be used in any other arrangement approved by the local or State Building Commissioner; provided, further, that pressed-brick facing when not counted as part of the bearing wall, may be laid without header courses if anchored to the backing by metal ties of design, material, weight and quantity approved by the local or State Building Commissioner. 301. BRICKS, HOW LAID.] All bricks shall be thoroughly drenched immediately before being laid, unless laid in freezing weather. Both horizontal and vertical joints in all kinds of brick masonry shall be filled with mortar. 302. LIME MORTAR.] All lime used for mortar shall be thoroughly burned, of good quality, and be free from clinkers and cinders. It shall be properly slaked before being used in making mortar. Lime mortar shall be composed of one part of slaked lime paste and not more than four parts of clean, coarse sand. 303. ALLOWABLE PRESSURE ON MASONRY.] (a) The allowable pressure in pounds per square inch on stone, brick or concrete masonry shall not exceed the following: 700 600 1. First-class masonry-granite and 1: 3 Portland cement mortar... 1,000 2. First-class masonry-limestone and 1: 3 Portland cement mortar. 3. First-class masonry-sandstone and 1: 3 Portland cement mortar. 4. Coursed rubble masonry and 1: 3 Portland cement mortar 5. Common rubble masonry and 1: 3 Portland cement mortar 6. Portland cement concrete-1: 2: 4 mixture 7. Portland cement concrete-1: 221⁄2 5 mixture 8. Portland cement concrete-1: 3:6 mixture 400 300 500 450 400 9. First-class paving brick and 1: 3 Portland cement mortar. 400 300 250 200 300 250 200 150 150 cement and 1 part lime paste, and 5 parts sand 14. First-class sewer brick and mortar as in No. 13 15. First-class common brick and mortar as in No. 13 16. Ordinary common brick and mortar as in No. 13. 17. First-class common brick and mortar as in No. 13 18. Ordinary common brick and mortar as in No. 13 100 (b) In every isolated pier of stone, brick or concrete, the ratio of the least lateral dimension to the height shall not exceed 5, unless the allowable pressure per square inch, as hereinbefore prescribed for the material of which the pier is built, is reduced 5 per cent for each unit of increase in this ratio; provided, further, that the ratio of the least lateral dimension to the height shall in no case exceed 12. 304. LOADS ON WALLS, PIERS AND COLUMNS.] (a) The walls, piers and columns of all buildings shall be proportioned to carry the full dead load, and in addition thereto the full live load on the roof and at least the following percentages of the full live load on the several floors: Eighty-five per cent of the live load on the top floor, 80 per cent of the live load on the next to the top floor, and each succeeding floor below 5 per cent less than the preceding one, except that not less than 50 per cnt of the full live load on any floor shall be used. The above requirements shall apply to basement walls, piers, and columns as well as other walls, piers, and columns. (b) The foundations of walls, piers and columns shall be proportioned to carry the entire dead load and the above percentages of the live loads, except that in designing pile foundations and in determining the area of concrete caissons the following percentages of the live load on basement walls, piers and columns shall be taken: 75 per cent 50 per cent 25 per cent (c) In all foundations any eccentric loading must be fully provided for. 305. THICKNESS OF WALLS.] (a) All exterior walls, except curtain walls and except as provided later in this section, whether brick, stone, or solid concrete, shall have a thickness in accordance with the following schedule: (b) In buildings of Class IIa, all surrounding walls and all dividing walls carrying loads of floors and roof shall have thicknesses in accordance with the following table: (c) The basement walls of two-story buildings and the first story walls of three-story buildings in Class III may be 12 inches in thickness. The first-story walls of one-story buildings and the second-story walls of twostory buildings in Class III may be 8 inches in thickness; provided, that where a pressed-brick face is used no such wall shall be less than 12 inches in thickness. (d) An 8-inch brick or solid concrete partition wall may, be built in a building of any class where said wall is not more than 14 feet in height. (e) The basement walls of two-story buildings in Class III and IV may be 12 inches in thickness. (f) In buildings of skeleton fireproof construction, the thickness of walls shall be governed by the requirements of this Act for such type of construction, but shall not be less than 12 inches in thickness. (g) Walls less than 50 feet in length or less than 50 feet between cross walls, may be built 4 inches less in thickness than the thickness required by this section; but no such wall in such buildings shall be less than 12 inches in thickness; provided, that 8-inch walls may be used in one-story brick buildings and in the second story of two-story brick buildings of Class III where said 8-inch walls are not more than 14 feet in height and are supported by a foundation or wall not less than 12 inches in thickness. (h) The length of a wall shall be the distance in which the wall extends in a straight line and shall be measured between angles of the masonry or between exterior and cross walls. (i) A brick wall not more than 25 feet long and forming one side of a brick shaft for stairs, elevator or other purpose, need not exceed 16 inches in thickness, nor its upper 50 feet 12 inches in thickness; provided, that in no case shall the load on such brick wall exceed the safe load for brickwork prescribed by this Act. (j) Where masonry buttresses or piers or pilasters are employed on either or both sides of a wall, then said walls may be reduced in thickness by one-half of the projection or projections of the buttresses, piers or pilasters. The reduction in thickness may be made throughout the height of the wall, except that no 12-inch wall shall be higher than 30 feet and no 16inch wall shall be higher than 50 feet. The stress in the brick work in any part of such walls shall not exceed the stress per square inch allowed by this Act on the kind of masonry used. Buttresses, piers or pilasters shall be at least one-tenth as wide as the spacing between the buttresses or piers or pilasters. Twelve-inch walls or less between buttresses, piers or pilasters shall not be used where the distance between buttresses, piers or pilasters is greater than 18 feet. Sixteen-inch walls or less shall not be used between buttresses, piers or pilasters where the distance is greater than 24 feet between buttresses or pilasters. Twenty-inch walls or less shall not be used between buttresses, piers or pilasters where the distance is greater than 30 feet between buttresses or piers or pilasters. Where buttresses are used, they shall be so placed that the principal girders and trusses shall rest on them. (k) If the loads carried by trusses and girders are supported by iron, steel, or reinforced concrete columns, then such buttresses shall not be required except for the fireproofing of steel and iron columns. The walls between such columns shall be built as required by this Act. Said walls shall be anchored to such columns by metal anchors at every 7 feet of the height of such column. (1) A structural floor system shall extend from one wall to an opposite wall, and the walls shall be anchored to floor joists or girders or both with iron anchors placed opposite one another, secured to the same joists or girders in pairs, at every 7 feet or less of length of said walls. Where said joists or girders are of such length that it is not practicable to make them of one piece, then the several pieces shall be joined at each splice or joint by tie plates or tie bars or other metal connections of the same strength as the anchors. Such anchors shall have not less than four-tenths of a square inch of metal in the smallest cross-sectional area. The spikes, bolts or screws securing said anchors and tie plates, shall be of such number and size as to transmit the tensile stress which the anchor is capable of resisting into the joists or girders to which said anchors are connected. All pin anchors shall extend at least 8 inches into the supporting masonry. (m) Where 12-inch walls are used, the story height shall not exceed 18 feet. Where 16-inch walls are used, the story height shall not exceed 24 feet. Where 20-inch walls are used, the story height shall not exceed 30 feet. (n) Where the story height is greater than 30 feet, the walls shall not be of less thickness than the following: The upper 15 feet shall be not less than 16 inches in thickness, and the wall shall be increased 4 inches in thickness at each interval of 15 feet or fractional part thereof of height. (0) Curtain walls in skeleton-construction buildings may be of hollow clay tile of the same thickness as herein required for brick walls. (p) The walls of buildings to be used for the purposes of Class III, not more than two stories in height, may be of hollow clay tile or moulded hollow concrete blocks not thinner than the thickness herein required for brick walls, subject to the approval of the local or State Building Commissioner. (q) Interior brick walls used to support fireproof floor-construction, where brick walls are not required by this Act, may be built thinner than the thickness required by the provisions of paragraphs (a) of this section; provided, that the ratio between the thickness of such walls and the free height between floors does not exceed fifteen; and provided, further, that the unit stresses do not exceed the stresses allowed by this Act. 306. SUPPORTS FOR JOISTS.] If brick or stone masonry walls are used for the intermediate supports for joists, they may, in all cases where the thickness of walls is given in section 305 as 16 inches or more, be made 4 inches less in thickness than the dimensions stated. (b) Wherever iron or steel joists and girder boxes having five complete sides of iron, nowhere less than 1/4-inch in thickness, are used, corbels and ledges as herein specified may be omitted. 307. PARAPET WALLS.](a) On all buildings having flat roofs, parapet walls shall be erected, except as hereinafter provided, on all exterior walls and on all partiton walls required by this Act by reason of the area of such buildings, provided such parapet walls may be dispensed with on any walls of a fireproof building, and on street and alley walls, and on yard and court walls of other than fireproof buildings where the entire framing and materials of the roof are strictly fireproof, or where all portions of the roof nearer than 15 feet to the line of such street or alley or the line bounding such yard or court, are protected against fire by a continuous covering of porous or hollow tiles not less than 2 inches thick, surfaced with mortar on top of the roof boards. (b) Such parapet walls may be 8 inches thick wherever this Act permits the use of 8-inch walls; and elsewhere they shall not be less than 12 inches in thickness. (c) Such parapet walls shall extend not less than 3 feet vertically above the roof on all such required partition walls, and on all other walls within less than 3 feet of any division lot-line and approximately parallel therewith; and elsewhere they shall extend not less than 18 inches above the roof. (d) On all buildings whose roofs have a greater pitch than 3 inches per horizontal foot, parapet walls of thickness and height as above specified shall be erected on required partition walls, on exterior walls approximately parallel with and less than 3 feet distant from a division lot-line, and on walls abutting on another building; provided, such parapet walls may be dispensed with where the framing and materials of the roof are fireproof, or where the cornice and roof covering are of combustible material and the top of the roof boards is protected against fire for at least 5 feet up from such wall by a coating of plaster on porous or hollow tiles at least 2 inches thick; and provided, further, such parapet walls and such protection against fire may be dispensed with on buildings of Classes IIIb and IIId three stories or less in height when such buildings have cornices of incombustible material and a roof covering of slate or terra-cotta tile. 308. TERRA-COTTA TILE COLUMNS.] (a) Columns of solid terra-cotta or of hollow terra-cotta in which the sectional area of the open holes in each block shall not exceed 20 per cent of the gross sectional area of such block, may be used for structural purposes; provided, the height of such column shall not exceed twelve times its least dimension. (b) The allowable stress shall not exceed 350 pounds per square inch; and shall be subject to the reduction formula given in section 303, paragraph (b). (c) All terra-cotta tile used for construction of columns shall be hard burned and of uniform quality, free from shrinkage cracks, with true beds, and having ultimate compressive strength of not less than 6,000 pounds per square inch of the area of cross section of samples tested. (d) Mortar used in setting terra-cotta tile columns shall be composed of one part Portland cement and three parts clean, sharp, sand, thoroughly mixed. (e) All terra-cotta tile must be thoroughly wet before being used, and when used in columns must be set on end with the voids running vertically and directly over each other, and with the webs in direct line of pressure. (f) All work shall be set plumb, with uniform horizontal joints averaging three-eighths of an inch in thickness. The time which shall elapse between the finishing of the work and before any load is placed thereon shall not be less than seven days. 309. TERRA-COTTA TILE WALLS.] (a) Hollow terra-cotta tile may be used for bearing walls; provided, the free height between the floors does not exceed fifteen times the thickness of the wall; and provided, further, the load, including the weight of the construction, does not exceed 350 pounds per square inch of net sectional area of tile. Such walls shall be of the thickness specified by this Act for brick walls. (b) Hollow terra-cotta tile may be used for exterior bearing walls; but when so used the thickness and height of the wall must conform to the dimensions required for brick walls in this Act, and must in no case exceed four stories in height. (c) The thickness of walls shall be calculated as the outside dimensions of the tile, and each tile shall be the full thickness of the wall. The thickness of the plastering is not to be included as a part of the thickness of the wall. (d) The quality of the tile and mortar and the provisions as to workmanship of terra-cotta columns shall apply to terra-cotta tile walls. (e) Fireproof storage bins, grain elevators, and grain warehouses may be built in cylindrical form with terra-cotta tile of such height, diameter and thickness as is allowed by safe engineering practice; provided, the material shall not be stressed in excess of the limits prescribed in this Act for walls and columns. D. PLAIN CONCRETE. 310. PLAIN CONCRETE DEFINED.] Plain concrete shall be understood to be a mixture of Portland cement, sand or other fine aggregate, and stone or other coarse aggregate, without any reinforcing steel or other metal. 311. CEMENT.] The cement shall conform to the standard specifications for Portland cement adopted January 12, 1912, by the American Society for Testing Materials, and printed on pages 112-125 of the official proceedings of the 1912 annual meeting of that society. 312. SAND.] The sand shall be clean, sharp and coarse, and shall have grains varying in size. Not more than 10 per cent shall pass a sieve having 100 meshes per square inch; and all shall pass a screen of 25 meshes per square inch. It shall be free from all organic matter; but it may contain clay or loam not to exceed 5 per cent. Stone screenings may be used instead of sand provided they are screened so as to remove all dust and all particles over one fourth of an inch in greatest dimension. 313. STONE.] (a) The stone shall be screened to remove all particles less than one quarter of an inch in greatest dimension; and shall be screened to remove all fragments greater than 21⁄2 inches in diameter. The stone shall contain all the sizes between the preceding limits in their natural proportion. (b) If gravel is used, it shall be thoroughly washed. If slag is used, it shall be of such character that the concrete made of it will develop a crushing strength equal to that specified for stone or gravel concrete. 314. PROPORTIONS.] The proportions of the concrete shall be expressed by stating the number of cubic feet each of sand and broken stone to be used with one bag (94 pounds) of cement. 315. MIXING AND PLACING.] (a) The several ingredients shall be separately and accurately measured before being mixed. (b) The concrete shall be mixed until the mass has a uniform color, appearance, and consistency throughout. Enough clean water shall be used to make the mixture so wet that workmen in walking upon it will sink to their ankles. |