(a) Floor and Roof Framing.
(1) All girders, beams, and rafters shall be adequate to support the loads prescribed by Chapter 3129, without exceeding the allowable stresses specified in OBBC and this Building Code.
(2) Members supporting plaster shall be designed so that the deflection under the assumed live loading prescribed by OBBC and this Building Code shall not exceed one-three hundred sixtieth (1/360) of the span.
(3) When wood members which are not the heartwood of a durable species are to be embedded or rest within exterior masonry which is below the adjoining grade, the parts to be within the masonry shall first be treated with an approved preservative.
(4) When supported by masonry, joists shall have ample bearing but not less than three (3) inches. When there is not masonry above the bearing, the joists shall have a two (2) inch minimum fire cut or bevel.
(5) Masonry walls shall be securely anchored to each tier of wood joists or wood beams bearing on them at maximum intervals of four (4) feet by metal anchors having a minimum cross section of one-fourth (1/4) inch by one and one-fourth (1-1/4) inch, and at least sixteen (16) inches long, securely fastened to the joists or beams and provided with split and upset ends or other approved means for anchoring into masonry. Girders shall be similarly anchored at their bearings. Anchors shall be attached near the bottom of the framing members so as to be self- releasing.
(6) Masonry walls parallel to wood joists or to wood beams shall be provided with similar anchors at maximum intervals of six (6) feet engaging not less than three (3) joists or beams.
(7) Upset or “T” ends on anchors shall develop the full strength of the anchor strap and shall be solidly embedded in the masonry.
(8) Anchors may be omitted at the first tier of joists when the supporting walls are laterally braced by earth, or in other approved manner, and are bonded to masonry above.
(9) When enclosing walls are of wood, each joist, beam, and girder supported by the wall shall be securely spiked or anchored to the wall construction, so as to stay in place and to resist safely all lists and lateral pressures required to be assumed by OBBC and this Building Code.
(10) Girders shall be fastened to each other where they intersect or abut.
(11) Floor joists framing into the side of wood girders or headers shall be supported on metal joist hangers or on a bearing strip or ledger board of adequate size fastened to the side of the girders or headers. Such strip or board shall measure at least two (2) by three (3) inches in section. The notch in the end of the joist shall be not more than one-quarter (1/4) of the joist depth, and the shearing stress shall not exceed the allowable stress when calculated in the manner prescribed by OBBC and this Building Code. Joists shall be spiked to metal joist hangers. When supported on a bearing strip or ledger board, joists shall be spiked thereto and shall be further supported by spikes driven through the supporting member into the joists.
(12) The ends of joists, whether resting upon girders or bearing partitions or abutted against girders, shall be either securely tied to the girders or to each other, or lapped and spiked together, on not more than four (4) foot centers, so as to resist safely an outward thrust on the walls equal to the assumed wind pressure, or the spreading action of the roof, whichever is the greater.
(13) When joists are butted, ties shall be of metal not less than one-eighth (1/8) inch by one (1) inch by eighteen (18) inches, or of wood not less than one (1) inch thick and two (2) feet long. When joists are lapped to provide a tie they shall lap one another not less than four (4) inches and shall be securely spiked together. When joists abut a girder, metal dog anchors driven into the tops of the joists and not less than one-eighth (1/8) inch by one (1) inch in section, or metal straps not less than one-eighth (1/8) inch by one (1) inch by eighteen (18) inches, may be used. Ties shall be spaced not more than four (4) feet on centers and, for masonry enclosed buildings, shall be provided on each line of joists tied to enclosing masonry walls.
(14) All joists shall be spiked to the bearing when bearing is of wood.
(15) All joints of solid or build-up girders forming simple spans, except joints in approved glued laminated girders, shall be made over column or pier supports. When girders made up of joists nailed together side by side are continuous over three (3) or more supports, joints in joists shall be located between one-sixth (1/6) and one-fourth (1/4) the span length from an intermediate support. No two (2) adjoining joists, nor more than one-third (1/3) the total number, shall be joined on the same side of the support.
(16) Joists supporting one (1) story nonbearing partitions which are parallel to the joists shall be doubled. Members supporting nonbearing partitions more than one (1) story in height, or bearing partitions, shall be designed to support safely the superimposed load. Joists supporting a partition parallel to the joists and spaced apart to permit the passage of piping or ductwork shall be blocked on not more than four (4) foot intervals to provide support for the partition.
(17) Unless otherwise specifically approved by the Commissioner joists shall not be notched within the middle one-half (1/2) of the span, nor shall notches in the top or bottom edges of the joists in the outer one- quarter (1/4) of the span length exceed one-sixth (1/6) of the joist depth.
(18) Holes bored through joists shall not, because of location or by proximity to other holes or cuts, impair the bearing capacities of the joists so as to render them incapable of safely supporting the design load. Unless otherwise specifically approved by the Commissioner holes bored through joists shall not exceed two and one-half (2-1/2) inches in diameter and no hole shall be closer than two (2) inches to the top or bottom of a joist.
(19) All framing around openings shall be designed for the loads supported. In general all headers and trimmers shall be doubled unless single members are adequate for the load.
(20) A trimmer supported header carrying four (4) or more tail beams shall be rested on metal joist hangers spiked to the trimmer and the header. Headers carrying less than four (4) tail beams shall be supported on metal joist hangers or on bearing strips or ledger boards not less than two (2) inches by three (3) inches by twenty-four (24) inches well spiked to the side of the trimmer. When supported on a bearing strip or ledger board, headers shall be spiked thereto and shall be further supported by spikes driven through the trimmer into the headers.
(21) Joist Hangers. Metal hangers for joists, headers, and other framed-in wood members shall be of approved type, shall provide adequate and firm support, and shall be punched to permit spiking to the supporting and supported members.
(22) Support of Rafters.
A. Rafters shall be vertically supported near the ridge when the slope is less than four (4) inches per foot. Rafters, regardless of slope, shall be thus supported unless they are held from spreading. Where rafters are not otherwise held against spreading, collar ties shall be provided on every pair of rafters. If the spread of the rafters is prevented by ties not at the plate line, the size of the rafters shall be increased to take care of the additional bending moments induced by the ties when the roof is loaded with the maximum vertical load.
B. When ceiling joists do not serve as a tie at the plate line, ceiling joists or other ties on each pair of rafters shall be provided below the upper third and they shall be well spiked to each rafter.
C. Wood rafters shall be so spiked or otherwise fastened to the plate or other members, as to resist safely all thrusts under full load, and the upward lift; the minimum fastening shall be two (2) sixteen (16) penny nails at each rafter end, or the approved equivalent thereof.
D. Framing around roof openings, and hip and valley rafters, shall be designed for the loads supported. In general, double rafters and headers shall be used around roof openings unless single members are adequate for the load.
E. At ridges, rafters shall be framed against ridge boards not less than one (1) inch by eight (8) inches in size.
F. Plates supported by masonry shall be anchored to the masonry as required by OBBC and this Building Code for the anchoring of wood sills to foundation walls.
G. The tops of all walls shall be securely tied or anchored so as to resist safely all lateral forces including the horizontal components of loads on sloping roofs, the spreading action of rafters not tied at the plate line, and wind loads.
(23) Bridging.
A. Floor and flat-roof joists and beams shall be securely bridged at intervals not exceeding eight (8) feet between bridging or between bridging and bearing, either with diagonal wood bridging not less than two (2) inch by three (3) inches fitted and double nailed at each end, or with approved rigid metal bridging, or with solid wood bridging, or with other approved bridging providing adequate stiffening; except that when the required joist depth is more than six (6) times the breadth, joists shall be bridged at intervals not exceeding six (6) times the joist depth. Solid blocking shall be placed between joists at all joist supports whenever the joists are not otherwise laterally braced or fastened.
B. Where the required depth of rafters is more than six (6) times the breadth, the rafters shall be bridged as required for floor joists.
(24) Floor Sleepers. Unless heartwood of a durable species is used, wood floor sleepers or other wood embedded in or laid on masonry or concrete that is in direct contact with the ground shall first be treated with an approved pressure preservative treatment. Pieces shall be machined and cut before treatment whenever possible; when cutting after treatment is unavoidable, the cut surfaces shall be given two (2) brush coats of a suitable preservative.
(25) Roof Sheathing.
A. *All roofing materials, including wood shingles, shall be applied over closed solid sheathing or approved equivalent.
*Closed solid sheathing is required to limit, to some degree, the conflagration hazard from roof fires, and is deemed necessary in the City because of the closely built up nature of the residential areas and the proximity of industrial uses thereto.
B. Roof sheathing shall be of wood, or of other approved material providing secure attachment for the roofing and moisture-resistance and fire- resistance at least equal to that of wood sheathing.
C. Wood Roof Sheathing. Wood roof sheathing shall have a minimum nominal thickness of one (1) inch and shall be applied over maximum rafter spacings of twenty-four (24) inches on centers. Joints shall be over rafters unless end-matched boards are used; if end-matched boards are used, no two (2) adjoining boards shall break joints over the same rafter space and each board shall bear on at least two (2) rafters.
D. Plywood Roof Sheathing.
1. Plywood roof sheathing shall be applied with the grain of the outer plies at right angles to the rafters.
2. Plywood sheathing shall be not less than “sheathing” grade, “interior type,” conforming to OBBC.
3. Wood, slate, shingles, or tile roofing, applied over roof sheathing less than five- eighths (5/8) inch thick shall be fastened to wood or other approved nailing strips.
4. Plywood roof sheathing not of the exterior type shall have no surface or edge exposed to the weather.
(26) Flooring.
A. In all buildings with wood-framed floor construction where finished wood floors of wood less than three-fourths (3/4) inch in thickness are installed, and under all finished wood floors in such buildings more than two and one-half (2-1/2) stories in height, sub-flooring of wood not less than one (1) inch nominal thickness or plywood not less than five-eighths (5/8) inch thick shall be provided under all finished wood floors.
B. In buildings with wood-framed floor construction over two and one-half (2-1/2) stories in height double wood flooring or other equivalent diaphragm shall be provided and securely fastened to the floor framing for stiffening and to resist lateral forces.
C. For double wood floors or approved equivalent required for fire protection see relevant provisions of OBBC and this Building Code.
D. When double wood floors are required for fire protection, plywood subflooring conforming to OBBC, may be substituted for the one (1) inch nominal thickness wood sub-flooring.
E. When the sub-flooring serves as a structural diaphragm to resist lateral forces it shall be securely fastened to the floor framing system.
F. Wood flooring shall be of such thickness that it will safely support all design loads without a deflection exceeding one-three hundred sixtieth (1/360) of the span. The center-to-center spacing of supporting members under one (1) inch nominal thickness wood flooring shall not exceed sixteen (16) inches, and for double wood flooring shall not exceed twenty (20) inches.
(27) Plank and Beam Floor and Roof Construction, and Laminated Floors.
A. Nothing in this chapter shall be interpreted to prevent or preclude the use of floor or roof constructions consisting of plank floors or roof decking on supporting beams spaced more than twenty (20) inches on centers, provided that such construction is designed in accordance with good engineering practice and is approved by the Commissioner and all structural members are fastened together so as to provide a well integrated structure capable of supporting all superimposed loads and withstanding all lateral and other forces.
B. Nothing in this chapter shall be interpreted to prevent or preclude the use of laminated floors, consisting of wood members placed on edge and securely nailed together, in locations where wood flooring is permitted by OBBC and this Building Code, provided that such laminated floors are installed so as to perform all functions required by OBBC and this Building Code for wood flooring in such locations.