Connect Unistrut/Superstrut to the garage ceiling

garagescrewsstorage

I'm planning on building storage above my garage door using an 8' x 4' platform from plywood and 2x4s. One 8' side would attach to the garage wall with lag screws. The other 8' side would be attached to the ceiling with threaded rods.

The ceiling is sheetrocked and there is living space above the garage so I don't have access to the trusses. The trusses run perpendicular to the 8'x4'. The threaded rods will connect into Unistrut or Superstrut that is lag screwed into the ceiling trusses.

I have a couple of questions:

  1. The open part of the Unistrut is facing down of course. Do I put a fender washer inside the Unistrut and lag screw through that? Or do I purchase a large square Unistrut washer, which stays on the outside of the Unistrut bottom and screw through that?

  2. What size lag screw do I use? I figure my trusses are 1.5" thick I think. Plus 1/2" sheetrock and the thickness of the Unistrut. Should I go with 3/8" x 2" lag screws?

Thanks!

Best Answer

  1. I would recommend that you don't use a washer on the outside of the Unistrut bottom that has any chance of wedging the Unistrut open. The fender washer on the inside is definitely the simplest solution, and it has the advantage of leaving all of the unistrut opening clear for your platform hangers.
  2. The strength of your lag-bolt connection is based on the surface area of the threads. Therefore the length of the bolt is potentially just as important, if not more so, than the diameter. Remember, you have 1/2 or 5/8 inches of drywall that isn't giving you any grip, so your 2 inch lag bolt is only holding on by 1-1/2 inch or less. Your joists will be likely 8 to 10 inches tall. 5/16 x 4 inch lag bolts will give you more holding power than 3/8 x 2.
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