It’s not so much that they’ve changed, but rather that the guidelines are now much more comprehensive and useful. While the legislation changed in 2008, it was only in 2011 that Part L: Roofs was published by the SABS. The South African National Standard for Roofs This last one, though, is open to interpretation as not all roofs incorporate ceilings as such. Lastly, the General Requirements specify (as they did previously), that the roof should be designed “as part of a roof and ceiling assembly” and should provide “adequate height in any room immediately below such assembly”. In addition, the roof should be “adequately anchored against wind uplift” which was not covered in the previous edition of the regs. Instead of simply being “durable and waterproof”, roofs are expected to be “durable” and should not allow “the penetration of rainwater or any other surface water to its interior”.Īs previously, roofs must “not allow the accumulation of any water” (but not simply rainwater, which was the limit of the old building regulations) “upon its surface”. In simple language, if there is a major wind or some other really horrible weather conditions (God forbid), the roofs of our homes are expected to be able to stay on the house and protect us from the elements without themselves being damaged. When the South African National Building Regulations were updated by the Department of Trade and Industry in May 2008, the General Requirement relating to Roofs was changed to incorporate certain safety elements.įor example, instead of simply having to “resist any forces” to which the roof might be subjected to, the regulations now state that “The roof of any building shall be so designed and constructed that it safely sustains any actions which can reasonably be expected to occur and in such a manner that any local damage (including cracking) or deformation do not compromise its functioning”. Those using this Span Calculator assume all liability from its use.Building Regulations as They Apply to Roofs-Part L While every effort has been made to insure the accuracy of the information presented, and special effort has been made to assure that the information reflects the state-of-the-art, neither the American Wood Council nor its members assume any responsibility for any particular design prepared from this Span Calculator application. Buildings in these high snow zones should be designed in accordance with accepted engineering practice. Buildings in regions with ground snow loads greater than 70 psf should not use the prescriptive provisions of the governing building code without approval of the authority having jurisdiction.The Span Calculator does not address wind load or seismic load. Joists and rafters carry only combinations of dead load plus live load (D + L), dead load plus snow load (D + S), or dead load plus roof live load (D + Lr).Consult the local building code for specific requirements. These minimum bearing lengths are to be used in the absence of calculated bearing lengths. For joists and rafters, most building codes specify a minimum bearing length of 1.5 inches on wood or metal and not less than 3 inches on masonry or concrete.The Span Calculator does not address cantilevered joists and rafters, multiple-span joists and rafters, or spliced joists and rafters. Joists and rafters are single-span with adequate structural support at each end.At least three joists or rafters are installed parallel to one another and spaced not more than 24 inches on-center, with properly designed sheathing attached on the top (compression) edge of each joist or rafter.thick) face of the member, resulting in strong-axis bending. Joists and rafters are oriented to support vertical loads applied to the narrow (1.5 in. Maximum horizontal spans for joists and rafters are calculated based on the following assumptions and conditions: A span options calculator allows selection of multiple species and grades for comparison purposes. Joists and rafter spans for common loading conditions can be determined. The American Wood Council (AWC) Span Calculator for Wood Joists and Rafters (Span Calc) performs calculations for all species and grades of commercially available softwood and hardwood lumber as found in the 2018 National Design Specification® (NDS®) for Wood Construction. Calculator for Wood Joists + Rafters for all species and grades of commercially available softwood and hardwood lumber as found in the 2018 National Design Specification®
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