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• • <br /> STATE 04, <br /> oh 4 <br /> ,y'L 1889��y <br /> Washington State Building Code Council <br /> Improving the built environment by promoting health, safety and welfare <br /> 1500 Jefferson Street SE • P.O.Box 41449 • Olympia, Washington 98504 <br /> (360)407-9280 • fax(360)586-5366 • e-mail sbcc@gawa.gov • www.ga.wa.gov/sbcc <br /> STATE BUILDING CODE INTERPRETATION NO. 16-11 <br /> CODE: 2015 International Residential Code <br /> SECTION: Section R301.5 Live load—Table R301.5—Minimum Uniformly Distributed Live Loads <br /> Section R507 Exterior Decks <br /> QUESTION: The state amended the live load in Table R301.5 for decks and balconies from 40 <br /> pounds per square foot(psf)to 60 psf. <br /> The 2015 IRC Section 507-Exterior Decks, includes joist and beam span tables, and <br /> a ledger connection table,which contain values for live load on decks and balconies <br /> based on 40 psf. <br /> Does the state amendment include tables referred to in Section 507, to ensure deck <br /> construction is safely accomplished under the amended uniform live load in Table <br /> R301.5? <br /> ANSWER: No,the state amendment does not include amended tables. However,the revised <br /> tables included in this interpretation have been calculated assuming a 60 psf live load. <br /> The revised tables were developed using the engineering provisions in the National Design <br /> Standard(NDS), as published by the American Wood Council(AWC). In general,for Doug-Fir and <br /> Hem-Fir lumber(most commonly used in Washington): <br /> • Joist spans are reduced an average of 11%. (Range: 19%decrease to 19% <br /> increase. Median: 15%decrease.) <br /> • Beam spans reduced an average of 8%(Range: 30%decrease to 13%increase. Median: <br /> 5%decrease). Shorter joist spans most often resulted in no change or increased beam <br /> span. Longer joist spans mostly resulted in decreased beam spans. <br /> • Ledger bolt spacing reduced an average of 38%(Range: 17%to 48% <br /> decrease. Median: 44%decrease.) <br /> o Lag bolt spacing reduced an average of 29%(Range:27%to 30%decrease. Median: 28% <br /> decrease.) <br /> o Through-bolt spacing reduced an average of 42%(Range: 17%to 48%decrease. Median:47% <br /> decrease.) <br /> o Through-bolt(with%2"stacked washer spacers)spacing reduced an average of 43%(Range: 28%to <br /> 48%decrease. Median:45%decrease.) <br /> SUPERSEDES: None <br /> REQUESTED BY: City of Seattle <br /> I15 <br />