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Question DetailsAsked on 6/8/2014

A sagging ceiling question

Hello experts,

I have a quick question. Please see attached pic. Today when I was
replacing a light bulb, I noticed the ceiling around two alarms is
actually sagging a little bit. This is the second floor. So I went up
to the attic and pulled out the insulation. The drywall is dry. The
sagging area seems to be along the seam of two pieces of drywall which
is perpendicular to the joist. It may be like that from the let go.
Just like to hear your opinion. There is no cracks in the sagging area.

Thanks so much.

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4 Answers

Voted Best Answer

This is real common - many drywall installers install the sheets in the direction that gives the least joints, which can mean an edge is largely unsupported for its full 8-12 foot length. By code, a long edge crosswise to supporting beams or joists is supposed to be supported by blocking, but no one does that. Sometimes this appears at end joints too, but not so common.

This is something you can fix yourself, or a handyman with some carpentry skills or a carpenter could do it. What I do is one of two things, depending on whether the ceiling has a special texture or covering to it or not and if flooring can bear some weight, with proper padding.

Simple solution is to use smoot plywood scraps, with old blanket or towel over the top to protect the drywall ceiling, and wedge 2x4's underneath (protecting your flooring) to press the drywall back in place - being careful the plywood piece spans the joint evenly so you do not move one sheet vertically relative to the other and crack the seam tape. Then when it is snugly up against the ceiling joists, I go into the attic and install nailed-in 2x4 or better yet 2x6 scraps flat face down between the joists as blocking, snug down against the drywall. If the joint is already damaged so the tape joint has to be redone you just put in regular drywall screws along the sheet edges from below, into the 2x6 blocking. If ceiling is undamaged like in your case, I put full-coverage Liquid Nails on the face of the pieces of blocking before putting the blocking piece in place, so it holds the top face of the drywall in place after drying - meaning the supports should stay in place for a day before removal.

If ceiling surface would be damaged by props (particularly with decorative metal or recessed wood panels on ceiling) then I use a piece of 1/2" or 3/4" thick plywood in each joist bay sized to fit freely between the joists - about square and with a bit of slack on each side, and screw it with large wood screws into the face of a piece of 2x6 blocking, which will be centered over the drywall sheets joint. I then glue the plywood down to the drywall with liquid nails and let harden - doing this in each joist bay where the drywall is or might start coming down. Then, next day, I install Simpson 90 degree heavy duty angles to the joist sides centered on the drywall joint, with a 1/2-3/4" gap under the angle piece (above the 2x6) at each end. Then, using screws through the angle piece into the 2x6, I carefully, working all around a bit at a time like tightening engine head bolts, tighten the screws so it gradually and evenly lifts the drywall up until it is snug under the joists and you cannot run a piece of paper between the joists and the drywall any more. Sort of like using a vacuum lifting tool to handle a piece of glass, but permanently affixed, and leaves no mark on the ceiling below if down right.

Two things can happen with this process that mar your ceiling - the joint tape can break or rip, causing a visible joint crack. Secondly, when pulling the drywall up tight, existing nails or screws can poke through the drywall, requiring that you reset them deeper and patch the popoouts, of course repainting in both cases as well.

In your case, considering where it hapened, it is possible someone leaned their hand on the drywall or kneeled on the insulation and popped the drywall down a bit - though it could mean the sheet has too few nails or screws holding it along that edge and it is starting to come down, too. Hard to guess which it is. This also sometimes happens because of frost buildup on or in the insulation during the winter, which evaporates in the spring, leaving no visible proof of it excecpt some matting of the insulation and maybe a touch of white mildew on top, but progressively pushes the drywall down, eventually pulling the screws or nails through the sheet.

If you have no visible damage not and don't want to risk popouts or seam tear by pulling it up, you could do the 2x6 and plywood thing (the second case above), but instead of pulling the drywall up tight to the joist bottoms, just tighten the screws enough to carry the load of the drywall in case it is trying to drop down, and leave the existing sag there as is.

Answered 5 years ago by LCD


Answered 5 years ago by shiyang100


Thanks LCD. I definitely will try your suggestions.

Answered 5 years ago by shiyang100


By the way, LCD, I just went up to the attic and noticed the installer did put a piece plywood along the seam of two sheetrocks. Do you think the sagging may mean something else? Thanks.

Answered 5 years ago by shiyang100


If the plywood is glued or screwed to the sheets then it should hold the joint even - i.e. prevent differential offset relative to each side, which might be why it is there. But unless it is fastened rigidly to the joists to hold the drywall up tight to the joists, then it would not prevent the sagging. This may be something that was done as a prior fix for separating joints, or to try to fix your problem but did not pull it up at all.

Check under the joists - if there is a gap between the joists and drywall all along that area comparable to your sag, then the drywall sagging is the issue. If tight to the joists, then check to see if you have cracked joists - might be damaged along the length of the joists that run through the sag area, though normally near the center if due to loading rather than wood defects. Or if joists are exposed, just eyeball along the top to see if dramatically sagging in that area.

Assuming the joists are good, then gluing the plywood to the drywall (if not already glued or screwed to it) and then putting in a "strongback" to pull it up snug to the joists may be all you need. Safer (less likely to crack) to do it by propping the drywall up from below with padded plywood scrap to spread the load, or having someone with strong back and arms hold it up using a stepladder while you screw into the plywood from above. Remember coming from above you only have the thickness of the plywood plus half or less of the drywall thickness for the screws for penetration length, so unless 3/4" plywood you may have to glue a 2x scrap to the plywood to give enough thickness for screws to get a good grip. Then use metal brackets off the joists to screw through and pull the plywood up, or you can use metal angle brackets nailed Teco nailed or screwed to the joists to form ledges gapped a bit above the plywood, and put a 2x scrap across them spanning between joists and screwed to them. Then run appropriate length screws down through drilled holes in that brace piece into the plywood or plywood/glued scrap to pull it up tight. The screws have to turn freely in the brackets or upper brace piece (predrill larger than thread) so they can spin in it freely as the screw bites into the glued on piece below, pulling it up.

As previously mentioned, if you pull it up tight it is quite likely existing nails or screws will "pop out" through the drywall and need recessing, then drywall patching with spackles or joint compound and repainting. Therefore, if you just want to stop more sag but can live with the existing, then the bracing and screwing in the attic should just be enough to get a good bite into the plywood with several screws to prevent further sagging, not actually pull it up tight to the underside of the joists.

Answered 5 years ago by LCD

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