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Context

As I am installing new drywall, I have done some research about drywall screw patterns. Surprisingly, I found all sort of data about it. Recommendations for 4x8 sheets range from 24 screws to 40 screws. 16in on center for walls, 12in on center for ceiling. Some recommendation start on the very edge, some 8 in from the edge. I would like to understand the why behind these patterns.

Questions

  1. Why is it recommended to start screws 8in from the top edge of a horizontally laid drywall for walls? Does that apply to each sheet or just the top ceiling one? Why?
  2. Why is it recommended to start screws 7in or 8in from edge for ceiling sheets?
  3. Why others recommend to place screws less than 1/2 in from edge for tapered and butt joints both for walls and ceiling?
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  • what is the reason for horizontal monut ?
    – asinine
    Mar 3 at 5:02
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    @Ruskes there is an old post with about 15-20 answers on it. That post is a holy war of Horizontal v Vertical mounting. Go look it up at your own risk.
    – FreeMan
    Mar 3 at 16:09
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    Below the surface and w/o popping the paper. If it pops you must remove it and put one next to the hole you made. Five, on every stud it contacts, w/e that is. One at the top, one at the bottom, one in the middle, two in between. Butt joints: +1/2" away from the edge, angled ~25 degrees towards the stud (these will pop the paper a little, ideally just not all the way around). - If it pops the paper then it's not secure, which is fine really for one screw, except that the little pug of mud in the hole is sitting over an anvil and will eventually crack the paint.
    – Mazura
    Mar 4 at 2:01
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    Where's all this "eight inches" coming from? could be talking about the first screw you do while you're hanging it. Which is the first one from the top one, on like the second or third stud, after you've held it firmly against the wall with your fist and then made sure the bottom was in with your foot. Then the same thing on the second to last stud, again use your foot. Third screw is the first from the bottom screw while you're still there, then go do that to the first side. Now you draw lines with your square hung on the top and fill in the rest. Upper sheet sits on the one below.
    – Mazura
    Mar 4 at 2:23
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    Same thing for ceiling because once you get those four screws in you can let go (which you do not sink fully until the rest are in). If those four screws are 1/2" in each direction to the corner then you cannot let go or it will fall. For walls you're just trying to work your way out from the middle kinda, which is best practice. For ceiling you also need to not get crushed while hanging it.
    – Mazura
    Mar 4 at 2:26

2 Answers 2

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The extra space at the top of wall/edge of ceiling area is to reduce cracking due to building movement. Incidentally, the ceiling should be up first, going to the wall framing, and should end up resting on the wall sheet butted below it. The corner joint is held by the tape & mud and the extra distance to screws allows a little bit of flex before things start to rip/crack/tear as normal levels of framing movement occur.

This is established good practice for 30 years or more, but of course the building trades accept things so slowly that someone will be on momentarily to insist that they both must be screwed right to the edge, whatever research the Gypsum Panel Association completed decades ago be damned.

Ceilings have more screws because they are fighting gravity (and if there's insulation above, supporting more weight than just the panel). Walls simply need to be held in place, not held up. Screw schedules can also be reduced (or supplemented) by using adhesives.

1/2" from the edge is somewhat at risk of breaking out the edge of the panel, so you have to be careful; but if you are trying to make a butt-joint on 1.5" framing, 1/2" is pretty much what you need to both hit wood and hold the panel, though it's close on both counts. Where you have length rather than width of the framing to hit, coming back an inch or more from the edge is safer.

That is one reason I like putting 1x3 strapping on where practical - it's a much bigger target than a 1.5" edge. It also allows 12" support with 2 foot truss spacings for ceilings, and more structure to support modern levels of attic insulation, which can weigh quite a bit.

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Why is it recommended to start screws 8in from the top edge of a horizontally laid drywall for walls? Does that apply to each sheet or just the top ceiling one? Why?

On walls at least, the boards can rest on boards below in most cases. If you're doing top-down work, this advice doesn't apply. Ceilings either.

Why is it recommended to start screws 7in or 8in from edge for ceiling sheets?

Mostly support. You want to get the center of the board supported ASAP (so it doesn't fall), then work out from there.

Another reason is to provide a way to salvage the board if you have a mishap. If you start one close to the edge and drop the board (as an example), having one deeper in the board means the screw likely tears out cleanly, leaving you a small hole to patch after you re-mount it. Starting closer to the edge might tear a chunk out of the board and make it harder to salvage.

Why others recommend to place screws less than 1/2 in from edge for tapered and butt joints both for walls and ceiling?

One word: studs. It's probable (with 16-inch centered studs) you'll be butting ends up on a stud. In those cases, you'll be attaching the boards pretty close to the edge. Since you'll be taping and mudding, any mishaps here will be easier to hide.

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