Deck Live Load requirements in Washington State Amendment to the 2015 IRC

Wenatchee Home Inspections

Want to build a deck? Many people do or have it done. If you are in Washington state you should be aware that you live load requirement was amended. Washington State amended the live load in Table R301.5 for decks and balconies from 40 pounds per square foot (psf) to 60 psf.

Washington revised the tables that included in this interpretation have been calculated assuming a 60 psf live load.

From Washington state
“The revised tables were developed using the engineering provisions in the National Design

Standard (NDS), as published by the American Wood Council (AWC).  
In general, for Doug-Fir and Hem-Fir lumber (most commonly used in Washington):

• Joist spans are reduced an average of 11%.  (Range: 19% decrease to 19% increase.  Median: 15% decrease.)

• Beam spans reduced an average of 8% (Range: 30% decrease to 13% increase.  Median: 5% decrease).  

• Shorter joist spans most often resulted in no change or increased beam span.  Longer joist spans mostly resulted in decreased beam spans.

• Ledger bolt spacing reduced an average of 38% (Range: 17% to 48% decrease.  Median: 44% decrease.)

• Lag bolt spacing reduced an average of 29% (Range: 27% to 30% decrease.  Median: 28%

decrease.)

• Through-bolt spacing reduced an average of 42% (Range: 17% to 48% decrease.  Median: 47% decrease.)

• Through-bolt (with ½” stacked washer spacers) spacing reduced an average of 43% (Range: 28% to 48% decrease.  Median: 45% decrease.)”

Here are the tables which this amendment is about.

From the 2015 IRC live load table (unamended)

Washington State’s amended table

http://apps.leg.wa.gov/wac/default.aspx?cite=51-51&full=true#51-51-0301

Here is  the span tables from Washington State to show the corrected values for lumber.

Hope this helps and have fun building!!!

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If you find any errors or have additional information that would expand on any code, building standards or manufacturer requirements please let me know.

NCW Home Inspections, LLC  is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…  

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