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Drywall: 1/4" gap near the floor?

63K views 26 replies 12 participants last post by  Gary in WA 
#1 ·
Is there a specific reason I am supposed to leave a 1/4 " gap on the bottom when hanging drywall?
I haven't got an answer other than "that's what I was always told to do but I couldn't tell ya why". :eek:
That is why I am here because there's nothing about it in the DIY "bible" I bought and I haven't found any information online other than "oops" cover-ups.
Another question. Which should I do first: the drywall or the floor? I wouldn't think it would make a difference, but that's why I'm asking since I don't know for sure.
Thank you!!
 
#6 ·
It is a glueless interlocking hardwood floor that has a rubber backing, is "100% waterproof", "ideal for kitchens, bathrooms, and basements", "anti-bacterial", "sound absorbant", and ""requires no underlayment". At least that is what the box says but it is a "New" product that Menards carries so the clerk couldn't tell me much about it.
 
#10 · (Edited)
The actual reason for the 1/4" at the bottom (in truth it is 3/8" in a perfect world) is very simply to allow for typical variances in the measurements between the floor and the ceiling. Floors are never perfectly flat. This little bit of space allows you room to fit the sheet in.

But there is a problem with this that may catch you unawares.

Precut studs that most homeowners buy at Home Depot or Lowe's are sold cut to a length of 92 5/8". This is not long enough for single top plate walls.

Follow with me: Your drywall is 8'... 96". So your wall has to be taller than that. But, when you nail together a 92 5/8" stud and a top plate of 1 1/2" and a bottom plate of 1 1/2", what do you get? That's right, 95 5/8". Too short.

So you have to plan for a second top plate to go on the wall. And, actually this is proper. A doubled top plate now gives you a 97 1/8" tall wall.

You only have to put 96" of drywall on that 97 1/8" wall. This leaves an inch and an eighth left over. Have you screwed up?

Nope.

The reason is that your wall boards are supposed to be installed AFTER the ceiling boards have been hung. They actually support all the perimeter of the ceiling boards because you do NOT fasten the ceiling boards in the areas up close to the walls. You leave at least a foot of the edges of all your ceiling boards "floating" (unfastened), and slightly drooping.

There are a couple of big and important reasons for doing that..... but we are just discussing wall height right now.

So, you are going to support the previously installed 5/8" ceiling board with the wall boards. That further reduces your wall height to 96 1/2". Now you have a 1/2" gap.

But you are going to find that when you lift the top horizontal board (the only way to hang drywall correctly), not all of the ceiling boards will be right on the same plane. Some will be a little higher than others, some will be lower. It is this top horizontal board that levels out that variancy to help create a visually perfect and virtually straight ceiling-to-wall intersection up there. This is how you keep your edge up there from looking like it is undulating up and down like a roller coaster.

By the time that the top boards are hung on the wall, they will almost magically give you room for that necessary gap at the bottom..... which will be about a quarter of an inch.

And that gap is important for helping you hang the bottom board.

You can buy a TOE Jack like the one pictured below (about 16-17 bucks) to jamb under the bottom boards as they sit on the floor. This makes it SO easy to lift the bottom boards with your strong leg muscles so that you can easily get a tight fit between boards.

So, now you have it in a more complete version. Yes, you need that gap.
 

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#17 ·
Hi there,
New to this forum and excited to be here!
I can say from our ongoing project that you should definitely do the floors last! We laid a really expensive tile floor first thing after demo (my contractor Sister in law nearly had a heart attack, and now I know why). We have spent probably double time on every project looking after the floor- covering it up, sweeping, keeping tools from falling on it, and trying to keep it clean. Thank goodness we haven't grouted yet- the drywall has been a mess, and we still have primer and paint to go. It has been a lesson learned the hard way- next time, the floor will be the last project. Good luck!
 
#19 ·
Yeah, I'm a thinker. Lol! I had planned on leaving the gap, so my new question is how do I lay the different layers of flooring and make sure that gap is there? Just cut the drywall to 7'8" since the walls are 8', hang it snug against the ceiling, and lay the floor under it when the process is done?
I like to know full details about things because I live in the middle of nowhere and I can't get anyone who knows what they're doing to come help me. Which is why I'm so HAPPY to have found this website!! :)
 
#22 · (Edited)
You can hold the subflooring cuts as much as an inch back away from the drywall (assuming it ran all the way down), and you only need to hold the actual finished flooring a quarter of an inch or so back. The baseboard will easily cover that. Flooring isn't going to shrink, it only expands, so it will always be under the baseboard.
 
#27 ·
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