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Drywall compound thickness

Monte_Main | Posted in General Questions on

While doing some final finishing on drywall, I realized that a pedestal sink will be mounted to the wall, and that part of the wall is not planer. That is, due to a stud that is warped inward, there would be a 3/16″ gap at one end of the sink. I considered just using caulk, but the curve will be visible directly above the sink and below the mirror.

To make that area look flat, I’ll need to fill up to 1/4″.

I considered taking down the drywall and starting over, but that will add 1-2 weeks.

Can I just lay down 3, 1/16″ layers? I’ve never had to fill more than 1/8″ of compound, so just want to know if that much thickness will still stay in place?

Should I attach something like a lath /mesh to support that much compound?

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Replies

  1. Ryan_SLC | | #1

    Removing all and replacing isn't the only thing. You also could cut it open and shim the 2x4, block around that 2x4, and reattach a new small piece. Old drywall goes on the blocking, new small patch goes directly on the shims. Flat.

    Not compound because it shrinks through evaporation. "Easy Sand" doesn't shrink (much) because it's chemical. Multiple layers of Easy sand, it won't crack..

    Another material that isn't drywall to fill in the space, but I assume it's very uneven. The filler (masic, paper, cardboard, plastic) doesn't have to be contiguous, the hot mud will be the smoother. Just something to build up but not directly smooth. Plywood does come in paper thin and up widths too.

    I'd probably just hot mud it, maybe two times. I think number one is the best answer though--cut out just a small area to shim out the area and replace with a new piece. Both would look the same, so cutting it out might just be academically best.

  2. andy_ | | #2

    Just float it. Any restructuring is likely to create more issues at this point and floating out a 1/4" is not that big of a deal.

    Use a "hot mud" instead of a drying compound for the thickness, but be careful not to over do it as chemical set compounds like EasySand are anything but easy to sand.

  3. Ryan_SLC | | #3

    Agreed. Watch the Vancouver Carpenter on how not to float a large area and you'll be totally fine.

    1. Monte_Main | | #6

      Thanks for the reminder about the Vancouver Carpenter. I couldn't find a video with that title, but I did find "MUD FRAMING!! How to FIX CROOKED WALLS!!!". Clearly 1/4" is no problem. In the video "Mud Framing!!", Ben builds up 1/2" in a single pass without a worry. Vancouver Carpenter uses a darby and a boat load of compound.

      I realize that I've been lucky in all my previous drywall work that the walls were generally flat and plumb. I easily achieved a flat surface by working up to a 12" knife.

      The old walls I'm dealing with here are a different matter. After the initial taping, I should have switched directly to filling in with a darby or similar and just loading up on compound.

  4. Expert Member
    BILL WICHERS | | #4

    My preference would be to shim out the bad stud. Sometimes thin strips of luan, or single plys peeled off of a piece of plywood, will work for this. If you can't do that, then hot mud (the powder stuff you mix with water before using) will work, but it will take some time to build up a thick layer and then spread it all out. I have ocassionally added some mesh tape into those larger areas to help with cracking too.

    Note that hot mud comes in different "speeds". Don't bother with the 5 minute stuff for anything but small patches. I usually use the 45 or 90 minute stuff. This lets you build up several layers in one day, since it sets chemically and not by drying.

    Bill

    1. Monte_Main | | #7

      Thanks for specifying which setting compound to use (45/60).

  5. Expert Member
    DCcontrarian | | #5

    Drywall is usually made flat, not plumb. Making it plumb can be tricky. What I've done is mark out on the wall the four corners of the thing you're going to hang and put a drywall screw in each corner mark. Turn the screws so that the thing sits plumb against all four, that defines your plane. Then fill with setting type compound flush with the heads, and then taper away to get the rest of the wall flat.

    You can take the screws out or leave them depending on how it's going to be finished.

    1. Monte_Main | | #8

      I was thinking this way since I'd seen the same technique when pouring self-leveler, but not sure it was a good idea for drywall. Thanks for the reinforcement / encouragement!

  6. Ryan_SLC | | #9

    Just drywalled a new beam and wall repair on both sides. I like Easy Sand. However, my 20 and 90 were almost no different in uselessness.

    I'd suppose there is absolutely no detriment to a higher level. It's more likely a concern for a professional trying to knock out an area in one day.

    1. Expert Member
      BILL WICHERS | | #11

      If you have any old mix in the bucket when you mix the stuff, it tends to make it set faster. ALWAYS clean the bucket WELL before mixing the next batch.

      The reason this stuff is popular commercially is that you can get two, and sometimes three, coats on in a day. With the premixed stuff, you're usually limited to one coat a day. I probably use mostly 45 and 90 minute stuff, sometimes 20 for smaller jobs. The idea is to try to get a balance of work time to batch-making so that you can get enough done before it sets too much that you need to mix another batch. The goal is usually to be able to get at least two coats done in a day. For larger jobs, I mostly use the 90 stuff (i.e. new drywall work). For patches I'll use 20. I'm not sure I've ever used the 5 minute stuff at all, but I can't see it being good for anything more than patching small holes, and even then, only when you only have a hole or two to patch.

      Bill

  7. Ryan_SLC | | #10

    This is the Vancouver Carpenter video I was thinking of. If that actually applies, who knows :D

    Haha, "uh oh, we're getting low on liquid wall!"

    https://www.youtube.com/watch?v=ExrlG2c2KtI

  8. walta100 | | #12

    3 coats of the 45 minute drywall compound with a fan blowing on it and the wall will be flat in 4 hours.
    https://www.homedepot.com/p/USG-Sheetrock-Brand-18-lb-Easy-Sand-45-Lightweight-Setting-Type-Joint-Compound-384210/100321610

    Walta

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