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I am redoing a bathroom, converting a tub to a shower and I plan to install green-board above. The existing 1/2" drywall has some issues (flaking paint, nail pops). I'll be replacing the walls and the obvious choice would be to tear the ceiling out and replace it too.

But because there is loose cellulose insulation above the ceiling, I'm considering just applying a second layer of drywall (using long screws) on top of the current ceiling.

I'll be adding a vent fan, and I'm prepared to cut through two layers for that. I'm also changing overhead lighting so I'll probably use box extenders.

I've seen double drywall done for fire protection, so I know it's possible. Is it a bad idea in this situation? What problems might I encounter?

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  • What is structural framing spanning over your bathroom and at what spacing and what is the span? (i.e.: 2x4’s at 16” on center spanning 8’?)
    – Lee Sam
    Apr 1, 2021 at 23:45
  • 2x8 on 16" centers. I'll check the span. I see where you're going on the load calculation, thanks.
    – jbbenni
    Apr 2, 2021 at 12:31

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I don’t see any problem, with multiple changes I believe it is a better way to go. Even using an electric blower to move cellulose when I pulled it down there was still a mess. The others we did were overlays.

In a bathroom is 1 place I suggest using hot mud or setting compound for those new to Sheetrock. Hot mud is affected less by moisture than standard mud. Get the 1 hour stuff not the 15 minute and when it starts to set, toss anything that's left in the pan and mix a new batch.

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    There's nothing wrong with 2 layers of sheetrock. In fact, a friend of mine is doing a new house build in Oregon, there is a shop/garage in the first floor and living space on the 2nd floor (sloped lot, daylight basement). The AHJ is REQUIRING 2 layers of sheet rock on the ceiling of the shop/garage for fire protection.
    – George Anderson
    Apr 1, 2021 at 22:57
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    There's something wrong with it if the ceiling is up to the task. The fact that your friend's garage is doesn't mean all are. Over a large area that's thousands of lbs. of unexpected weight. Here, it's fine, but it's not an automatic yes.
    – isherwood
    Apr 1, 2021 at 23:04
  • @isherwood Gotcha! Thanks. But in his case, the TGIs where spec'd and engineered for 2 layers of sheet rock. Yeah, that's a ton of weight and expense that will probably never be used. Local codes are of course what need to be followed. I was just contributing the fact that there's nothing wrong with 2 layers of sheet rock and was even required in some places. Nothing more than that. Thanks again for your comment.
    – George Anderson
    Apr 2, 2021 at 1:14
  • Yes, it's smart to review the engineering because of the added weight. Will do. I was not familiar with hot mud, and will check it out. Thanks!
    – jbbenni
    Apr 2, 2021 at 12:32
  • Hot mud or setting mud relays on a chemical reaction to harden where basic mud it’s just the water drying out. Normally I suggest new to Sheetrock DIY’s not to use it (except bathrooms). My dad proved this to me by taking a chunk of hot mud and regular mud and putting them in water. The regular mud dissolved and there was milky looking water. The hot mud was still a chunk. This showed me that hot mud was moisture resistant. I don’t recommend it for large areas as most DiYers try to work it two long and make a big mess.
    – Ed Beal
    Apr 2, 2021 at 14:13
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i see no problems other than the new fan may have some tabs that fold out to install it above the drywall and with 2 layers, they may not work right. add some blocking and prepare to drill your own install holes in the metal housing of the fan........Maybe :)

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