Garage Attic Floor Joists - DIY Chatroom

zacmac · 11-02-2009, 10:53 AM

My garage attic space is constructed of a truss system (2x4) with 2x4 floor joists. I would like to finish the floor for storage above my garage, but the 2x4 construction has me concerned. Will it hold the weight of a person (I'm 250 lbs)?

Would adding scabs between each joist add strength to the floor or am I just wasting time and money?

I don't plan to live up there, but want to be able to walk around to move things around.

Any thoughts on the strength of the existing floor. Thanks in advance

eisert · 11-02-2009, 07:52 PM

The 2x4 "floor joist" is actually called the bottom chord. It will certainly hold your weight, but trusses with a 2x4 bottom chord are not designed to have a floor installed on them. If you put plywood up there and use it for storage, you risk exceeding the maximum load rating of the truss, damaging your roof structure or causing the truss to fail.

vsheetz · 11-02-2009, 10:48 PM

I have similar trusses in my workshop - I put down a few sheets of 1/2" ply and store only light stuff there. Christmas decorations, sleeping bags, empty boxes from electronics items, etc. I am not concerned of the weight.

Being over your garage, and if you are concerned, is there anyway to run a beam perpendiclar underneath?

NailedIt · 11-02-2009, 11:07 PM

Adding a beam underneath wouldn't help, but it would be unacceptable in terms of altering the structural design of an engineered member. I weigh about the same as you, plus carrying a framing nailer and tool belt weighed down full of tools and nails, and walk around inside roof trusses, actually standing at times on one individual 2x4 bottom chord and I've never had one come apart. I wouldn't store too much up there or you might end up with it crashing down on somebody when they're not looking.