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The attic above my garage has several of these horizontal support beams across the ceiling joists, I assume to keep them from bowing. I’d like to put down plywood across the whole floor without these because they’re a tripping hazard.

support beams

beams2

joists

Are these supporting pieces necessary? Can they be replaced by plywood and still keep the joists from bowing?

Just to clarify, I’m not referring to the beams holding up the roof, just the non-load-bearing ones.

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    Those are part of the frame. In my area they call it a strong back to help with spans were the joist ,maybe on the small side and help with the load. Not sure of than span ,or the real size of your joist. Looks like it was framed not to be plywooded and a load added to it . Never heard of hoist support? Or did someone have a hoist and mount it there. – user101687 Jun 6 at 23:57
  • Joists are double 2x12s in the main span, I think as an option for another bedroom. The supports are 2x4 flat with a 2x6 vertical. Outer skirts of the attic have single 2x12 or 2x10 that appear less load worthy – Chris Mendez Jun 7 at 1:31
  • How far do they span? Outside wall to outside wall, or outside wall to a beam ?Are they 2x12 or 2x10? – user101687 Jun 7 at 1:48
  • Joists span outside wall to inside wall separating attached garage. Joists are doubled 2x12s spaced 24”. Beam things are just stuck in the center between where the two garage doors would be. Maybe it’s related to the garage doors but it’s a two car tandem garage and there’s another supporting beam along the smaller span above the single spot. – Chris Mendez Jun 7 at 2:24
  • Do you have a tape? How long are they? 12 feet, 16 feet And more pics wont hurt. – user101687 Jun 7 at 2:30
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They seem to be 2x8, spanded out to the max,with strong backs added to help the frame.Witch is fine for a ceiling joist,to only handle ceiling load. Now you take the strong backs off weaken ceiling joist frame. Want to add plywood more weight.and you make them floor joist,if any load or a room is added due to span you may be under sized. If 2x10 and short span maybe fine .2x12 16 inches on center ,I would say your fine. After finding out you have a 20 foot span .2x12 24 on center changes things they are spanded out to the max.and strong backs added to help them . Adding plywood and taking out strong back not a good idea. Not a good spot to store stuff.

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    Fully agree at that span the strong back not only adds some strength but stabilizes everything and will prevent ceiling cracking and possibly collapse with them removed. I would consult an engineer or possibly add support from below but that was the reason for this to allow clear span. + – Ed Beal Jun 7 at 20:50
  • 10-4 on that. out of my league. – user101687 Jun 7 at 20:56
  • @EdBeal so are you saying that plywood can’t replace the function of a strong back? What about replacing one single 2x6 with multiple 2x4s that have plywood on top? Surely that would provide equivalent stabilization – Chris Mendez Jun 9 at 1:35
  • Not laying flat it can not, rim joists are made out of plywood but come in special lengths, laying the plywood flat just increases the load and provides no support other than from 1 joist to another the excessive weight could have it all coming down when some one walks across it without the strong back in place. – Ed Beal Jun 9 at 21:55
  • If you must walk down.Put two 2x12s on the flat,With 2x6 on the sides.Leaves strong backs and ,a walk way. Attic needs a beam.to much span for plywood. – user101687 Jun 9 at 22:17

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