Grout instead of thinset

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Jason1969

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I put up cement board in the shower and accidentally used grout for the seams instead of thinset... is this ok? I figure I'm going to be waterproofing it with RedGuard and putting thinset over it when I install the tile any way... If it's not, then how would I get it off?
 
I dunno. But your waterproofing is coming into play way to late. Don’t trust a sealer to water proof tile. Waterproof wall then begin your setup. Baker board is not waterproof. Sealer wears off after so many times of cleaning. Then in 10 years your walls fall on you while your taking a shower. And apparently there are some tile guys here so maybe your in the right place and me answering helps spread the thread
 
I'm talking about the seams of the cement board... I'm supposed to tape them, use thinset to fill in the seams and then waterproof... I accidentally used grout instead and I need to know if this is ok before I waterproof it. I haven't even started to tile yet....
 
Thinset is actually an adhesive, whereas grout is not. I would guess your seams will fail over time. If you cover up the wall with a good membrane system (I use Kerdi) you will make it moisture-proof, but the mechanical integrity of the underlying wall structure won't be what it should be. All in all, treat the wall as though you had never seamed them.

If you installed the cement board with screws (you DID use screws, I hope), just take out the screws, give the board a little shake, and the seams will fall apart. Brush off the grout with a wire brush (or probably even a stiff scrub brush), screw the board back up, and do the seams again the right way.
 
I'd leave the grout. Just tape the seams and use thinset over the seams. Then Redgard, then tile. How is your pan constructed?
 
I think it would be fine. Making good seams is more important for floors than walls. No one will be walking on your walls. Or maybe I shouldn't make assumptions, I'm not sure what's going on over there!

But think about it this way. Kerdi, for example, is designed to go directly over drywall. They recommend not doing any seams at all on the drywall. So I'm sure your walls would be OK. In fact I would not have done the seams to begin with on shower walls. You simply don't need any extra strength if there is not going to be any force pressing on it. It does not need to be structurally sound like a floor does. It just needs to hold up the tile.
 
Maybe we are talking about tile around a tub and not a shower stall?
I would second the idea of just taping over with thinset then waterproofing.
Once you bond the tile to the wall with thinset, the tile and backer board become one solid structure. As long as the tiles span across the areas with grout, everything will be locked together. If you are using a mosaic tile I might have a concern but otherwise should be ok.
 
Well, you need a Kerdi pan (they call it a tray), unless you want to mud one yourself.
 
Well, you need a Kerdi pan (they call it a tray), unless you want to mud one yourself.
Not so. I've contoured both raw concrete and wood, and put either the Kerdi membrane or Kerdi Ditra over that. Starting on another wood floor next week for a barrier-free shower. Having said that, using Schluter's tray is a lot easier, but you're quite limited in what you can do.
 
I'm sorry I should have been more specific... it is around a tub... I did start taking the grout off with a wire brush like originally suggested... it's not that hard, just messy and time consuming is all... I'm not using a mosaic tile either.
This is the first time I've ever done anything like this so I'm making some rookie mistakes along the way but I'm learning a lot as I go and having fun doing it as it's in my own house. When I did the new plumbing for the new fixtures I told people I don't think I've ever been more scared of anything in my life than I was to turn my water back on... Lol... but all is good.
I didn't think the grout would come off that easy actually once it dried so honestly I don't mind a little extra work to make sure it's done right.
I truly appreciate all of you taking the time to help me... Seriously, it means a lot to me.

Sincerely,
Jason
 
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I'm sorry I should have been more specific... it is around a tub...
Tub or shower, it's a tiled wall that's going to get water on it, so it has to be done right. The seal between wall and tub will be the tricky part; I can't offer any help with that.
 
Make sure your sub wall is not going all the way down to the tub lip. Water will wick up and ruin your job. After all, the tile will go down to the tub, but will not wick up.
 
The seam in the board doesn't matter. What matters is the waterproofing, including the cement board. If using Kerdi, leave the Kerdi a little long and attach it to the tub lip with KerdiFix or similar elastomeric sealant. The finished tile will cover this small area and the finished result is completely waterproof.
 
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Not so. I've contoured both raw concrete and wood, and put either the Kerdi membrane or Kerdi Ditra over that. Starting on another wood floor next week for a barrier-free shower. Having said that, using Schluter's tray is a lot easier, but you're quite limited in what you can do.

Concrete is not a great choice for a shower pan, but could loosely be included by what I called "mudding". A mortar base is standard and Kerdi is fine over that. Wood however is not an appropriate substrate for Kerdi. There is no such thing as Kerdi Ditra, so I assume you meant Schluter Ditra. Ditra is approved over wood of course - it's an uncoupling membrane so that is the point of it. Kerdi is not an uncoupling membrane and should be used over dimensionally stable stubstrates such as drywall or cement board. So just because you've done it, doesn't mean it's warranted or appropriate :)
 
Make sure your sub wall is not going all the way down to the tub lip. Water will wick up and ruin your job. After all, the tile will go down to the tub, but will not wick up.
I made sure to leave a gap... My understanding it gets caulked after all the tile and grout is done...
 

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