cement board to drywall joint

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Old 02-07-16, 05:36 PM
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cement board to drywall joint

Hi all,

I'm almost done putting up all the cement board in the bathroom I am remodeling.

I have cement board going up around 2ft over the bath tub edge and then I'm using drywall all the way up (12ft ceiling). I have it all set but I noticed that some people put 2x4s to support the horizontal edges of the durock and drywall in between the 2x4s. Is this absolutely necessary?

Thanks!
Tom
 
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Old 02-07-16, 06:29 PM
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If you plan on tile on the walls, you will need cbu all the way up as far as you run the tile. Sheetrock is not an approved substrate for tile. Maybe I misunderstood your post. Clarify if I did.
 
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Old 02-07-16, 07:41 PM
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Hi there,

I checked with multiple folks, mapei tech support, johnbridge forum and I have never ran into people having issues tiling over sheetrock. There is some prerequisites, flatness, surface prep for mechanical adhesion, primed to help moisture control etc. MAPEI said all their thinset will work, just to use their primer to make sure i maintain their warranty.

I am planning on tiling over the sheetrock btw. Thanks for your help.

Tom
 
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Old 02-08-16, 03:33 AM
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If this is a wet area, you WILL have problems with the tile and wall. With that said, and your insistence on tiling over sheetrock, I am not sure why you are asking us questions regarding it. You can install perlins across the horizontal edges of any wall covering and have super support, although it is not always required.
 
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Old 02-08-16, 03:42 AM
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If it's just a tub, the 2' height is fine but if there is a shower - no way would I tile over drywall!!
 
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Old 02-08-16, 10:07 AM
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There is no shower, just the tub. Chandler, thanks thats exactly what I was asking.
 
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Old 02-08-16, 12:39 PM
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In my house the back bathroom had a large shower stall. When the home inspector did his thing he stated that there was 30% moisture behind the tiles and that the whole shower should be demolished and rebuilt. He went on to state that he seriously doubted that any backer board had been used in its construction and that most likely it was just ordinary drywall behind the tile.

He was flat-out wrong. While the tiling was suspect, the contractor had used three different sizes and styles of tile, when I tore it out I found ZERO signs of any moisture behind the tiles. The base was a traditional mud bed, the liner was brought up at least a foot above the base and it was standard cement board (like Duroc) up five feet from the top of the floor. Above the cement board was green drywall to the ceiling. The shower head was mounted high, so high that the gooseneck came through the drywall above the cement board. Again, I stress that there was absolutely no sign of any moisture behind the tiles OR the drywall OR the cement board.

I am NOT trying to state that Chandler or Mark are wrong, I fully agree with both of them. Just that what APPEARS to be an inferior method of construction CAN work just fine for many, many years.
 
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Old 02-08-16, 02:04 PM
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Joel, in your instance you had CBU up to 5' in height. I was concerned with evilcat having a shower and only using CBU up two feet, which would present problems. Knowing it is only a tub, I see no problem in the plan of CBU up 2', then drywall the rest of the way. I didn't know that at first.
 
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Old 02-08-16, 09:21 PM
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Yep, the backer board came up to 5 feet but the shower arm was at 6 foot-six and through drywall. The tile, as I recall, went all the way to a dropped ceiling at about 7 foot-six. So still at least a foot and a half of tile on drywall that could get sprayed on a daily basis.
 
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Old 02-09-16, 04:11 AM
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Still, the majority of the water that might get thru the tile/grout is going to concentrate on the lower portion. Back when tile over green board in a shower was prevalent - the water damage was almost always limited to the bottom portion of the surround. When there is exposed drywall above the tile and often the shower arm is in that area, as long as the drywall is painted with latex enamel it's rare for moisture to deteriorate that drywall.
 
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