(a) For the purpose of providing ordinary framing methods and spans in this Building and Housing Code, joist and rafter span tables have been inserted based on identified graded lumber. The unit fiber stress and modulus of elasticity shall be recognized by the Department of Agriculture’s Forest Products Laboratories using a deflection factor not to exceed 1/360th of the span between supports.
(b) Floors shall be designed to support the dead load plus a live load of not less than forty pounds per square foot.
(c) All roofs for one, two and three-family dwellings shall be designed to sustain the dead load plus a live load of thirty pounds per square foot for roofs with a pitch of three and one-half to twelve, and forty pounds per square foot if the roof has less than a three and one-half pitch.
(d) All members shall be framed, anchored, tied and braced so as to develop the strength and rigidity necessary for the purposes for which they are used.
(e) Preparation, fabrication and installation of wood members, and the glues, connectors and mechanical devices for the fastening thereof, shall conform to good engineering practices.
(f) The Natural Design Specification for Stress-Grade Lumber and the Fastenings, 1971 edition, National Forest Products Association, shall be accepted as prima-facie evidence of good engineering practice covering design and use of stress-grade lumber, glued laminated lumber and their fastenings.
Lumber standards and grade marking shall be as follows:
(1) Softwood framing lumber and board lumber shall comply with the Voluntary Product Standard 20-70, American Softwood Lumber Standard, and with specific grading requirements of the association recognized as covering the species used and under whose grading rules it is produced.
(2) All lumber used for load-supporting purposes shall be identified by the grade mark of a lumber grading or inspection bureau or agency approved by the Board of Review of the American Lumber Standards or by the Canadian Lumber Standards, except that pre-cut material, rough-sawn lumber and lumber thicker than two inches may be identified by a Certificate of Inspection in lieu of grade marking.
When unit stresses for the species of wood are used other than those specified, the sizes of members and spans shall not exceed those determined by good engineering practice and shall be clearly set forth on all plans to be approved by the Division of Building and Zoning Inspection.
(Ord. 42-1981. Passed 2-23-81.)