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I’m putting up 5/8” 4x8 sheets of drywall on my garage ceiling. I am finding the 24” center on rafters not all exactly 24”. So when I am butting up sheets some barely are able to get a screw into the 2x4 on the edge of the sheet. I find it hard to cut a 3/4” slice off the edge of the drywall. What is the best way to deal with this?

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  • 1
    Are they exactly 24" on the ends, but get a little wonky in the middle?
    – JPhi1618
    Apr 3 '20 at 16:05
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    If you don't have too many that are off, might you consider sistering on a few 2x4's as nailers? It might take a bit of planning to see if the joist spacing issues are cumulative or not. Apr 3 '20 at 16:19
  • That might be the case. But I'm on the second row off the wall so not sure if I can square them back up to exactly 24" now? A 2"x4" is really a 1-1/2"x3-1/2" So I only have 3/4" of each sheet to get a screw into the 2x4 on the edges.
    – Eriksat1
    Apr 3 '20 at 16:20
  • if the ends are 24" but not the middle you might consider adding support 2x4 between joists to enforce 24" (also depends on the warp)
    – depperm
    Apr 3 '20 at 16:21
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    Since 1/2 way done your only choice is sistering this is what George Anderson suggested (adding another board to the side you will want to use screws because nailing will tear up the Sheetrock that’s already up.
    – Ed Beal
    Apr 3 '20 at 19:14
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I would suggest that you install 1x4 furring strips (example not a recommendation) across the joists. Use the picture below as an example. enter image description here

Notes:

  1. 24" is too far apart to install 5/8" on a ceiling. It would sag over time especially in a garage where there are more humidity and heat changes. So even if they were dead on - still a bad install. No inspector near me would OK this (yes I know its a garage and might not be inspected).
  2. I use 1x4 furring strips on basements and garages for ceilings when I need to. I have used 1x3s and what I have found is when you screw into the edge of them you can split the strips or crack them. Furring strips are cheap wood - give yourself the extra inch. The cost comparison is pretty negligible - might cost $10 more for the garage.
  3. The wider furring strips allow for you to install hooks and things easier too once the drywall is up.
  4. If there is a room above the furring strips will help you hold the insulation. Make sure to make rigid boxes to separate lighting before drywalling - much easier to do this beforehand.
  5. If your walls (drywall) isn't up yet make sure your furring strips near the wall are about 6 inches out - you do not want to screw the edges down. This will allow for movement and the drywall on the walls should support this.
  6. These furring strips since it is 5/8" and a ceiling should either be 12" or 18" on center. 18" is probably adequate for a garage. You need at least three tie-in rows.
  7. If you have a nail gun this is about 30 mins of prep for a garage. You can use a chalk rope to snap your grid and you should only have 10 or so cuts. This 30 mins of prep will make installing the drywall on the ceiling be twice as quick.

Side Note: Concerning point #1 - I am not disagreeing about the ability to install the drywall on 24" on center. But I have done a lot of houses. Most are 24" on center, most/all old ones have cracked seams. Most have no strapping or blocking. So sure put the drywall up and watch all your seams crack over time. And when your seams crack there isn't a long-term fix - yes you can always remud the seam and it will crack again. The fact is you will hang stuff in garage, you will have insulation on top of the drywall, you will be hanging shelves, you will probably have a garage door opener. Yes the garage does not have to be the Taj Majal but doing a tiny bit of prep is the right way. You can certainly do a substandard install and say "it's the garage". The point of my answer is the furring strips are cheap and easy to install AND make the install much easier and last longer. I have done this to any garage or basement that I have redone - (basements are a great example - if I do a basement without furring strips you can for sure see the bumps on the joists after a bit no matter how good of a job you do. I am not saying anyone without inspecting it and staring at the ceiling would notice but hey I can see it. If you use furring strips almost impossible to notice.)

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    @isherwood - I added a not to the answer - not trying to be Mike Holmes here and overdo everything but this is common practice for me even on the cheapest flip.
    – DMoore
    Apr 4 '20 at 20:46
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Best way - 1x3 strapping at 90 degrees to the vaguely located rafters (bottom chords), precisely located.

Note that you can center the strapping at 24, 19.2, 16 or 12 inches, as desired, and that at any spacing it gives you 2.5" ("dressed" or planed 3") of target surface, not 1.5" as your dressed/planed 2" bottom chords do. If you were planning to insulate on top of the drywall, strapping on a spacing closer than 24 inches can increase the amount of insulation you can safely support, though that's unlikely to be a limiting factor in most garages.

Probably too late for that unless you want to take down what you have got up and do-over.

A "cut-out tool" ("Drywall router", to stay away from brand names while providing an alternate search term) with a fence that you may need to create rather than find in the stock kit could potentially cut back to the center of the rafter (bottom chord) more easily (if messily) than using a knife - but in that case, what happens when one is long, not short? Will you be throwing away nearly half a sheet?

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I assume that you're talking about ceiling joists (truss bottom chords) and not rafters. If they're rafters, obviously you can't move them.

  • Pull the ceiling joists into position. They're floppy. If the carpenters nailed down the "rat run" without doing layout, you might pull the nails in that, lay out the joists properly, and re-nail.
  • Add sistered backing where needed.
  • Shorten sheets to the previous joist as needed. It seems wasteful, and it is a bit, but maybe less so than using a bunch of lumber and time.
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  • Yes I meant the joists not rafters. I have to go do some more measurements and if it is really bad I like the idea of pulling nails on the "rat run" and re-nail with the proper lay out. I'm hoping it is just one warped joist. I don't think the builder ever though a ceiling would be put up.
    – Eriksat1
    Apr 3 '20 at 16:52

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