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matt4321 10-05-2008 07:21 AM

Attic Decking
I bought a home several years ago that was manufactured in the early 1990's. It's in one of those neighborhoods that goes up fast, and I'm sure the contract spared every possible expense (no extra anything). At any rate, the attic space of the two-car garage when we moved in had several pieces of attack decking down, and I've added decking to 1/4 of the beams.

The reason I didn't go any further with the decking is there are a multitude of electrical wires that run on top of the beams. The beams are 2X4's that are part of pre-fabricated trusses, 24" on center. I was going to drill small holes in the beams (like you would do in studs) so I could run the wires between them and not over them, allowing me to add some more floor decking. However I did some quick online research and learned in an electrical forum that you NEVER, under any circumstances, drill holes in a prefabricated truss.

Now, I could run the wires on top of the decking I guess, but if a small hole in a beam is going to cause a that big a problem, how well can these trusses support the decking and storage items I'm placing up there? There are definitely NO engineering specs available. Is the decking OK, and what kind of load can this realistically support. Everyone stores a ton of crap in there attic space, right?



Square Eye 10-05-2008 07:38 AM

Pre-fab trusses are not rated for decking unless they're ordered with the specification that they will have a decked attic space. In a no-frills home like yours, I seriously doubt they are rated for decking and any attic load at all. Generally speaking, because I have no idea what span between bracing members on your trusses, the "floor joists" would be 2x6 or larger on a deck rated truss.

Decking and loading an attic not rated for those loads will void any warranty on the truss and could cause damage to them that you won't be able to detect until it's too late.

inspectorD 10-05-2008 07:38 AM

Sorry Matt, they should have also told you about truss construction.
You should not have any storage between them either. A roof truss is a system, and if you stress any part of the system, holes, cuts , modifications or weight where it is not supposed to be, you could end up with failure.

I would find somewhere else to store things. A light box of wreaths or ornaments may be OK, but for an accumulation of heavy stuff, I would find another spot.

Also if you are in an area which needs to be insulated, you will not get it with a 2x4 worth of space.

Welcome to the forum.:D

matt4321 10-05-2008 04:44 PM

Glad I asked!
Uggh. Well, at least I'm glad I asked before going any further. The space does have "pull-down" stairs for attic access - I guess they are there so you can you view the beauty of the pre-fab trusses.

Thanks for the comments. Definitely not the answer I wanted, but one I will heed.


inspectorD 10-05-2008 05:16 PM

OH no
Dont tell em there is a pull down, I hope they did not cut the trusses?

Please tell me they fit them between.:eek:

Sorry about the bad news, we don't like to give it out, but it saves you in the long run.
On another note, making sure those pull down stairs are insulated will help with your energy costs. is one maker.

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