# Cement board meets drywall?



## AtlanticWBConst.

CowboyAndy said:


> Do I need to mud/morter the seams of cement board to cement board?


Yes. You should use fibergalss mesh tape and thinset.



CowboyAndy said:


> what about the seams where the cement board meets the drywall?


Those seams may be treated as standard drywall seams. You can coat over the cement board portion of the seam, just as you would normal sheetrock.



CowboyAndy said:


> Tape? what material do I use?


 You can use standard paper tape and joint compound.


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## CowboyAndy

Thanks man, appriciate it.


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## CowboyAndy

One thing I forgot to ask, do I need to use different screws for the cement board?


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## angus242

If you are installing tile over the cement board, the CBU should be installed with alkali-resistant screws and then an alkali-resistant mesh tape be used over the seams. A coat of thinset would be used over the tape. 
If you go to a big box store, the screws and tape are usually in the tiling section. Typical screws are called Hardi Screws and the tape should be near by.
You may want to venture over to the tiling section of this forum to get some really good advise on water proofing! When a surround is water proofed, no chance of leaks and therefore, no mold!

Good luck!


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## trav2001

I have a friend getting ready to do this same project. I'm going to go over there today to take a look at what he's got going. I think he too wants to use cement board around the tub and then tile it. But I think he is okay to use the greenboard for that plus tile later. I'll be helping him with the project, so we'll see how it goes


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## oh'mike

Green board is not to be used in a wet area----No longer allowed by code in most places--to many failures.


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## epson

Using green board drywall in a wet location is a recipe for disaster. At the very least, severe mold growth will occur, if not outright failure of the product and green board drywall's paper covering is water resistant, it is not waterproof. Not only that, but the brittle gypsum core is not suitable for wet applications. A cement based product like Wonderboard or Hardibacker is suitable for tile covered wet applications like showers and tub surrounds.


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## trav2001

Wonderboard was the final descision. Will be starting that in a day or two


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