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Posted by Bob Morrison on May 14, 2007, 5:49 pm
In a previous post HerHusband wrote...
> > I recently purchased a house in Upstate, NY with a 2x4 roof truss
> > system in a detached garage. The interior dimensions of the garage
> > are roughly 24' x 24', and the trusses are constructed using plates to
> > connect the 2x4s. There is no bottom center support -- it looks like
> > two 12' 2x4s are connected at the middle via a plate on each truss.
> > Finally, the trusses are spaced 24" on center.
>
> > I just gave some thought to whether the truss system will be able
> > to handle the additional weight of insulation and sheetrock that
> > will be used?
>
> There's no way to know for certain without the specs from the company that
> made the truss. I had to include the truss specifications with my building
> permit, so you might be able to get that info from your local building
> department if you do not have a copy of the plans (for a research fee, I'm
> sure). The truss may also be stamped with the company name, in which case
> they might have records of that truss.
>
> In any case, every roof truss I have seen has always been designed for at
> least 10 pounds dead load on the bottom chord of the truss. A 4x8 sheet of
> 5/8" sheetrock probably weighs less than 80 pounds. That should work out to
> about 2.5 pounds per square foot. With insulation I'm guessing you'd still
> be under 3 psf (insulation is rather light). That still leaves plenty of
> capacity for light fixtures, garage door tracks and openers, etc.
>
> > The attic space won't be used for anything other than light storage.
>
> Personally, I wouldn't store anything on the bottom chord of a truss unless
> the truss was specifically designed to carry that load. But that's me.
>
Anthony has given a most excellent answer!
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
Structural & Civil Engineering
Poulsbo WA
bob at rlmorrisonengr dot com
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