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I have a textured ceiling similar to this:

enter image description here

Some of the texture peaks at 1/8", but it mostly peaks at 1/16". I am going to be applying a second layer of drywall with Green Glue in between and I want to know if all this texture has to be sanded down or scraped off before the second layer goes on.

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If you are adding sheets of drywall (plasterboard) then you're adding a lot of weight to the ceiling. Are you sure that a) the glue will hold the board up and b) the existing bonding between ceiling and joists is strong enough? –  ChrisF Feb 10 '12 at 15:27
    
Why do you need to add the second layer drywall? –  RSMoser Feb 10 '12 at 15:34
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ChrisF, Green Glue is not an adhesive, but a soundproofing compound. The drywall will still be screwed up into the joists through the existing drywall. RSMoser, that should have answered you question, too. –  oscilatingcretin Feb 10 '12 at 15:41
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Ah - I should have checked :) The name confused me. Make sure you use long enough drywall screws. We had a ceiling come down because the previous owners didn't. –  ChrisF Feb 10 '12 at 15:54
    
Yep, I'll be using 3" #8 coarse threads. That way, half the screw will go through the two layers of drywall and the other half will be going into the joist. This will be a good thing because my ceiling is already starting sag as it pulls loose from the nails, so this will help secure everything. –  oscilatingcretin Feb 10 '12 at 16:03

4 Answers 4

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The point of Green Glue is to create a flexible layer of never fully firm glue between layers of drywall, right? To absorb sound?

In which case, I think you'll need to first level the ceiling, then apply green glue, then apply your final layer.

Otherwise, if you green glue over top of the texture, you'll have high points in the texture that touch the new layer of drywall. That will transfer sound quite effectively - which you don't want.

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Good call on the texture peaks penetrating the Green Glue and coming in direct contact with the new drywall layer! The whole point of Green Glue is to separate two rigid layers, so it makes sense to smooth out the texture or even scrape it off altogether. The ceiling is definitely not level, though. How would one go about leveling a ceiling? –  oscilatingcretin Feb 11 '12 at 16:05
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It might be easier to apply a layer of mud over the entire ceiling to even it out versus sanding the texture off. –  Steven Feb 11 '12 at 16:29
    
You can level the textured ceiling with 2 to 3 skim coats of mud. First application, run the widest blade you can in a uniform direction - you'll get ridges in the mud like waves in the ocean. 2nd pass, run the perpendicular direction to fill in the ridges. In your case, that should do well enough to then apply the green glue. –  The Evil Greebo Feb 13 '12 at 1:46
    
As an update to this, what I ended up doing was spraying the ceiling with water and scraping off the texture after it got soggy. I didn't care much about getting every little bit, making it super even, or if I gouged the drywall since I am just putting on a second layer anyway. –  oscilatingcretin Oct 30 '12 at 19:53

Like Karl, I just riped the drywall out completely rather than trying to fix it in my own home. But if you go the pole sander route, then I'd measure out where the non-beveled joints are going to go (the 4' side of a 4x8 sheet) and just sand those areas, maybe 6" to either side of the joint. The drywall will bend in slightly at the joint and you fill the whole space with joint compound.

Also take a flashlight at a hard angle to see if you can find where the current joints are. Where you find the preexisting 4' ridges, sand them down. When you layout the new layer of drywall, stager the joints so you don't have two non-beveled joints on top of each other.

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It's not something you need to remove. However, how thick is the drywall that you're putting up? If it's 1/2 or 5/8", ok, but I'd be worried about how much weight you're adding. If you're putting up 3/8 or if you managed to find some 1/4", you're going to show every bump and ridge beneath it. You probably want to use half inch, and you might think about firring it out.

You still need to be aware of the slant of the ceiling to make sure that you don't bump outwards since that's hard to hide with compound. If you have to do anything, bow out in the middle of the board and then have your joints bow in.

I attempted to remove the same texture from drywall in my house, and it was a beast. i was using a belt sander with a 50 grit belt and it still wouldn't smooth down. I ended up tearing out the drywall and starting over.

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It's 5/8" type-x. It's about 75 lbs per 5x8 sheet, but I am going to be fastening each sheet with ample 2 1/2" screws, so it won't be coming down any time soon. –  oscilatingcretin Feb 10 '12 at 22:26
    
OK. The 5/8 will help smooth the bumps out. You still need to be aware of the slant of the ceiling to make sure that you don't bump OUTWARDS since that's hard to hide with compound. If you have to do anything bow out in the middle of the board and then have your joints bow in. –  Karl Katzke Feb 10 '12 at 22:37
    
+1 @oscilatingcretin for the 2 1/2" screws. Whenever we put up a second layer on the ceiling (fire code for the top level of our multi-units) we use long screws and make sure we hit the joists. All the load should be transfered to the joist and none of the layer of drywall above. –  BMitch Feb 11 '12 at 2:12

I would remove it, then your drywall sandwich has no gaps between it and will allow for better attachment. But its not popcorn so it may not be as simple as a scrape with a trowel.

If it is really a bear to take off, you could try a test piece without removing it and see how it looks and attaches. If the next ceiling is smooth, I would be somewhat concerned of noticeable peaks and valleys, but the only way to tell would be a test piece install.

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Yeah, I was sorta leaning this way too. 1/8 isn't a lot, and the texture will probably be flattened when the new wallboard is screwed up, but then again it wouldn't be very hard to run a pole sander over the ceiling and knock it down a bit. –  Steve Jackson Feb 10 '12 at 16:58
    
Ah, a pole sander. I didn't even know it existed. This would probably be easier than scraping it all off. –  oscilatingcretin Feb 10 '12 at 17:16
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@oscilatingcretin: You may want to look into a vacuum pole sander‌​. It will save you from a huge mess everywhere, especially when you mud the new ceiling. I wish I had bought one the last time I worked on my ceiling - I discovered they exist in Home Depot after I had just finished the last coat of mud. :/ Be advised, I haven't used a vacuum one, but I have used a regular pole sander. I'm also not hawking the specific one I linked to - just providing an example. –  Doresoom Feb 10 '12 at 17:32
    
Even more then better attachment, I'd hate to hit a stiff spot and have even out the drywall after hanging it up. –  Kris K. Feb 10 '12 at 19:16

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