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My cousin says I should leave 1/4" space between all edges of drywall so that mud can be pressed into it. Everything I've read online say to butt them tight. When is leaving a gap a good idea?

  • If there is ever a case to not butt them tight, it "could" be on a metal stud, on a poorly insulated wall? Or it you want room, in case you are sloppy with cuts? Can't really think of a reason to WANT to leave a gap. Even mud will crack with shifting. – noybman Feb 9 '18 at 4:53
  • Thanks, what are you thinking of regarding metal vs wood studs ? – Jerry Feb 9 '18 at 6:14
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    I'm just trying to cover an extreme where in a wall condition that you expect severe expansion and contraction that maybe you'd want gaps, but as I cautioned, and now others have answered, ultimately this doesn't buy you anything because mud when dry will crack. Thus... it just doesn't make sense – noybman Feb 9 '18 at 15:33
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    Smart to look be thinking of edge cases (pun not intended :) – Jerry Feb 9 '18 at 15:46
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    I've seen manufacturer specifications that require it to be closely fit (can't remember exact term) for use in firewalls, and I think sound as well. This doesn't matter as much in residential, though. Again, never seen an intentional gap. – Someone Somewhere Feb 10 '18 at 14:26
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It really doesn't matter, I would run them tight, it uses less mud. If a gap occurs, don't sweat it. It is better to run drywall tight into the corners, it makes taping easier than having a gap. I have never seen a drywall crew intentionally set gaps.

  • I guess if one aims to run tight joints, then gaps here and there look like 'failures'. But if one intentionally leaves gaps everywhere, then there are no apparent fouls. – Jerry Feb 9 '18 at 15:22
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    In setting drywall, the only failure would be leaving a gap that is too big, a gap that the tape could not cover. I have covered 1/2" gaps in drywall with no issue, it is not easy compared to tight gaps, but can be done. The biggest failure that could occur is not fastening the drywall well enough to the studs, the second failure would not having the framing sound enough or dry enough to fasten the drywall too. Both conditions will lead to cracks in the drywall finish, primarily in the corners – Jack Feb 9 '18 at 16:29
  • I would not leave gaps also although you are talking only a small amount it's that much less support from the stud, you want them as tight as possible a slightly bowed stud and then there is less to screw into.+ – Ed Beal Jan 2 at 22:28
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I think you run a pretty fair chance of pushing enough mud right out the back of a 1/4" gap that gobs of it will fall off inside the wall and be wasted.

You can (and should) squeeze drywall mud into pretty small cracks. Leaving a big gap just isn't a concern. Put a nice coat of mud under the joint tape, squeeze it into the joint, then put another coat over the top of the tape and feather it out. The mud will adhere to the drywall, fill the joint holding the sheets together, and the tape will be embedded inside the coat of mud strengthening the whole joint.

Drywall mud shrinks as it dries. The bigger the gap, the more times you'll have to go over the same seam with extra coats of mud to pull it out level with the wall. Otherwise, you would have a very visible groove running down the length of your wall.

Also consider that it's the paper on the front and back that holds a sheet of drywall together. The mud adheres well to the paper, to the drywall tape, and to any exposed gypsum on the cut edges of the panels when it is skimmed on.

But if you leave too large of a gap, you end up with bigger globs of mud, which you can knock loose in one chunk. You could actually bump that gap with something, like a furniture corner, and knock a line of joint compound loose from the edges of the sheetrock panels so that there's a flexible 1/4 strip of dried mud floating in that 1/4" crack, only being held in place by the tape on the front. I'm absolutely certain I've seen exactly that, at least once.

Set the sheets tight together. Like the other answerer, Jack, I've never seen drywall in any residential or commercial installation intentionally set with large gaps.

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    He didn't say why, but I suspect he thinks that mud squeezes out on the backside (like you say), keying the mud in-place and keying edges together like in lath and plaster.The difference, though, is mud cracks so easily because it is not fiber reinforced. If there is no good reason for gaps, and plenty of good reasons for no gaps (as the case seems to be), asking him would only lead to a debate which he wouldn't win. – Jerry Feb 9 '18 at 15:16
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    "Drywall mud shrinks as it sets." not quite accurate. Regular drywall compound dries, not sets, and the water evaporating causes it to shrink. Setting compound sets, not dries, and does not shrink. This is an important distinction because both types are commonly used and require slightly different techniques (and sense of urgency). – user4302 Feb 10 '18 at 5:57
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    Fair enough, but nobody is really talking about using anything other than drywall mud, right? I’ll change the word set to dry in my answer, though. ;) – Craig Feb 10 '18 at 12:26
  • @Craig I'm not sure I understand your last comment. Setting type drywall compound is still "drywall mud" as much as premix drywall compound is. A lot of professionals prefer it for a first coat because it does not shrink as it dries or sets and you can get onto a second coat sooner. Typically, setting type compound is set before it dries and it doesn't shrink as its drying either, so your updated answer is still not quite accurate on this count. – statueuphemism Mar 11 '18 at 10:50
  • I think this is getting pretty pedantic. ;-). Professionals won't be looking to this answer for guidance, the vast majority of people who run to Home Depot to buy a bucket of mud will end up with the usual type, which shrinks, and even if they don't, they don't want to leave a big gap along the edges for all of the other reasons I mentioned. – Craig Mar 11 '18 at 18:04
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Though I have seen in commercial construction (where walls are often 50-500 feet long of continuous drywall) where there are deliberate expansion joints set. These help control cracking on long walls (similar to putting expansion cuts in concrete). Typically there is a small gap between drywall sections which allow a special expansion piece to be mudded into place (similar to typical inside/outside corners used at the edges of drywall). It is then finished like any other joint, except that the expansion gap isn't filled in which allows the joint to flex slightly without cracking the drywall.

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(source)

Other than this, drywall sections should probably always be butted against each other and the joint finished with tape and mud.

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To me it would matter if you are hanging sheets horizontally or vertically. If they are horizontal it would not matter as much but if vertical having a space provides less support and a bowed stud may almost no room for screws without breaking the edge. In both cases I usually butt them tight.

  • good point on joints over studs benefiting from no gaps. – Jerry Feb 9 '18 at 15:08
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    Probably worth being more specific - if your studs are 16" on-center and you leave gaps, you will eventually have floating edges by the time you get to the other end of the wall. The math just doesn't work out in your favor. – user4302 Feb 10 '18 at 5:59
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After seeing the reference in a previous comment about the "Do's and Don'ts Of Drywalling" recommending a 1/8" gap, I decided to take a look at the reference. The gap is recommended for the edge of inside corner pieces that you need to cut. This is because if you cut it a little too wide, you can mess up the edge forcing it into place. It does NOT recommend gaps between full sheets. In fact is gives a photo of butt joints with no gap. The reference does have good points. If you are a novice, it is worth reading. Also, like several other people have noted, if you add 1/8" to every sheet, you're going to run out of studs to nail/screw to after a while.

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I typically leave a gap about the thickness of the taping knife, so 1/16th or less.

I also use "hot mud", which is the dry powder mixed with water that sets via a chemical reaction similar to concrete. It's MUCH stronger, harder, and holds better. I also don't use paper tape - I prefer the mesh tape as the paper tape never seems to bond well at all, regardless of any gap or no gap between sheets.

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ive been doing this 34 years and never heard of leaving a gap between sheets. just doesnt make sense. sheets are 4 x 8 typically and framing is 16 on center. like someone else said your run would grow even on just a few sheets across. i do alot of commercial drywall and we usually stand the sheets up so 4 ft 1/8 would grow fast in a big room. honestly never had a problem make them nice and tight , its a better job imo

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According to The Do’s and Dont’s Of Drywalling. One of the biggest mistakes is not leaving a 1/8 in gap in your joints .

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    Welcome to Stack Exchange, could you expand your answer by providing the reason why not leaving a 1/8" air gap is a "don't"? – statueuphemism Mar 11 '18 at 10:56
  • Is “The Do’s and Dont’s of Drywalling” a book or something? – Craig Mar 27 '18 at 15:22
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Most houses are 70F year round so allowing for thermal expansion isn't really something you need to worry about. If the space is unheated (and -20F) for weeks at a time you might want to think about cracking coming from thermal expansion/contraction.

Similarly, the paper on the outside of the sheetrock and a coat of latex paint seems little it would inhibit moisture induced expansion (unlike a hardwood floor, where expansion can make a too tight floor push a wall out of plumb!)

There's no reason to engineer gaps between sheets. It just makes the taping slower .

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