Decking On Bottom Chord


Can I put a wood deck (1/2 in. plywood) on top of the bottom chord of a 26 foot span truss 24 inches on center?


Whether or not you can add wood decking onto the bottom chord of your roof trusses depends on what load your trusses were designed for in the first place. What are you planning to use the wood decking 1/2 in. plywood itself only weighs 1.5 pounds per square foot (psf), which probably would not affect the integrity of the truss design. If you plan on adding dead weight from storing materials in the attic space, this may lead to problems. According to IRC 2012/2015 R301.4 and the Truss Plate Institute's ANSI/TPI 1, bottom chord dead load shall be the actual weight of the material. Typical bottom chord dead load is 10 psf for residential use. Is your bottom chord seeing a larger dead load than 10 psf?

If you have the original truss design drawings from the truss manufacturer, these drawings will provide the bottom chord load for which your trusses were designed. This will help you determine whether you can add weight in the roof system. For assistance, talk with the original truss manufacturer or check out our Members Section for truss manufacturer listings – one of our members would be more than willing to discuss your load situation.

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