oops joint compound on Durarock

[bself]

Hello,

My wife and I are remodeling our bath/shower and have gotten as far as installing the Durarock for the tub surround.

Due to a misunderstanding (I accept full responsibility) my better half mudded the seems with joint compound instead of thinset. How screwed are we?

Can I remedy the situation with RedGard or Laticrete (no vapor barrier)? Or am I worse (or better) off than I imagine?

--ben

[Brian in San Diego]

Ben,

It's gotta come out my friend. Sorry. Maybe by moistening it and using a putty knife you can scrape it out. You need to use thinset and alkalai resistant mesh tape to bond those seams. I used the word "bond" for a reason. You are making a monlithic structure upon which you will set tile. It isn't to waterproof...that's done by the redguard or whatever waterproofing membrane you are going to use (laticrete hydroban is another).

Brian

[Mike2]

Ben, when you say "no vapor barrier" what do you mean? If building a Kerdi shower, then it can be placed over drywall joint compound.

So...tell us why no vapor barrier and what kind of shower you are building.

[bself]

>> when you say "no vapor barrier" what do you mean?

Hi Mike,

It is just a simple tub surround: nothing nearly so ambitious as a Kerdi shower. The tub, a good old cast iron one about to be reglazed, should provide all the holding power. A base of Durarock on the walls from tub height to the ceiling is intended to provide support for the thinset and ceramic tile, but shouldn’t require much in the way of superior water proofing technology.

By no vapor I meant that it seemed like the jury was out on whether a vapor barrier was required behind the Durarock .. so paint me delinquent .. we didn’t put one up. In the event that something like RedGard is used, this appears to be recommended anyway. Although I’ll admit I wasn’t planning on using it until this came up..

>> You need to use thinset and alkalai resistant mesh tape to bond those seams.

And Brian: I got the alkalai resistant mesh tape part right, but since there was some drywall patching also required, the above misunderstanding resulted in joint compound instead of thinset being used.

Speculating a less than simple extraction, how bad would skimming thinset over joint compound be?

--ben

[ddmoit]

Is there a shower in this tub surround? If there isn't, then you probably don't need a moisture barrier. If there is, then you should consider using RedGard or a similar product on the surface of your cement board.

[ChrisIL]

Speculating a less than simple extraction, how bad would skimming thinset over joint compound be?

I think your gonna create a speed bump that will make it even worse. I'd wet the joint compound good and get ahold of the tape and pull it out. Sand down any residual joint compound and do it again with thin set. Joint compound it pretty flimsy when wet, and the water won't hurt the cement board.

Then I'd also use a moisture barrier over top the whole mess before tiling like Dan is suggesting.

[Brian in San Diego]

Ben,

If you used joint compound out of a box, then it will reemulsify when wet. Take a damp sponge and wipe it over the dried compound and look at the sponge. If you wet the compound it will come off. Yes, it's a little extra work, but it isn't the end of the world. The main reason you don't want to go over it with thinset (other than the bump it might make) is that the strength you are looking for is still in the joint compound and it isn't that strong. Start sponging that compound and rinsing your sponge in a bucket. As it gets wetter it's gonna get softer. Work it out either with the sponge or a putty knife. I agree with Dan, no shower...no waterproofing necessary.

Brian

[ckl111]

+1

Unless you used Durabond, you can remove the drywall compound with a large wet sponge and a bucket of water. A lot less dust than sanding. Being a tub surround, there couldn't be that many seams. The water won't hurt the durock at all.

[bself]

Thanks all for the help..

Scraping off the joint compound was no biggie, most of it is done already.

I had a brief pause when looking at the container and it was some generic brand labeled as 'spackle paste' (from the local mom and pop hardware store) fearing it had some #@$#!'n additive. But it reactivated easily with water just like the good old-fashioned stuff.

One last question before I am done..

I now understand that the thinset is required more to bond the Durarock together and provide a uniform surface than to waterproof the seams. What about the edges where it meets the drywall: can I leave some of the joint compound in to smooth the edge transition. Will the Redgard and thinset have any issues with a small amount of well sanded feathering overlapping the CBU by an inch or so?

--ben

[Brad Denny]

Hello Ben,
No problem with a little drywall mud on the board as long as it's outside the wet area. Just to confirm, this is a shower and you are going to paint the entire tub surround you will be tiling over with Redguard, yes?

[bself]

>> No problem with a little drywall mud on the board as long as it's outside the wet area.

Cool, that will give the best look.

>> Just to confirm, this is a shower and you are going to paint the entire tub surround you will be tiling over with Redguard, yes?

Yep, shower is in tow and Redgard will be liberally applied to the CBU after taping and thinset (doing that now)..

Hopefully the next time I check in will be on the flip-side of the project and I'll have pictures.

thanks,

--ben

[in2tile]

Note of caution.
dont apply red guard to dry wall compound outside shower, if bullnose or trim tile is to adhere outside shower ''on compound '' use oil primer over compound to seal joint, RED GUARD will peel right off any joint compound.
zinnser/stainblock is one choice, good luck.