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Taran7 06-14-2011 01:45 PM

repair durock imperfections before tiling
Hello -

I am installing Durock right now. I've tried a dozen times and still have some pretty minor bowing (inward) on a board or two. I'm wondering if I can live with that and float/correct it with some mortar or thinset prior to tiling, like I might do with sheetrock and mud?
I'm fresh out of shims. In fact if I see another shim I might jam it down my throat and be done with it.
It is a hotmop pan, doesn't yet have the cement float. (I know to not nail into the pan). I do have non-faced insulation up and am not using a vapor barrier, instead will at least double coat with RedGuard.
I'll be using 3 X 6 subway tile -- maybe that will be a bit more forgiving?
It's a 1940 house, the studs etc, are not square by a long shot.

thanks for any help! Taran

Bud Cline 06-14-2011 03:49 PM

Overall and at the deepest deep is this bowing?

It can be filled with thinset if it isn't too deep. Keep in mind thinset will sag if applied too thick. More than one pass may be required after the first pass has dried overnight.:)

Taran7 06-14-2011 04:03 PM

Thanks for the reply!

Maybe 10 inches or so, with a depth of no more than 1/8 inch...

and if that will work, is thinset the right thing to use to fill?

thanks again, Taran

Bud Cline 06-14-2011 04:19 PM


and if that will work, is thinset the right thing to use to fill?
What did I just say?:wallbash:

YES...use thinset and a straightedge bigger than the dip. That one is an easy fix.:)

Taran7 06-14-2011 04:23 PM

Terrific, thank you, good news.

Oh, and I forgot to ask --

Is thinset the right thing to use for this?


seriously, thanks -- Taran

Bud Cline 06-14-2011 04:37 PM

Glad to help. If I did.
Use thinset for the tile also.
You did know that...right?:)

Taran7 06-14-2011 04:53 PM


but since I have you here -- I am planning on mudding the corners and seams prior to putting the layer of cement on my pre-sloped hot mop pan, and prior to building the curb.

Is that correct? thanks again, Taran

Bud Cline 06-14-2011 04:58 PM


I am planning on mudding the corners and seams prior
Don't do that. When you begin your tile application that is the time to tape the seams then the mud used to apply the tiles is the mud that will cover the tape at the same time.

Otherwise you will have (hard) humps in the substrate and you don't want that. Especially with subway tiles. They will show up every imperfection in the substrate if it isn't totally flat/plane.:)

Taran7 06-14-2011 06:52 PM

Hmmm... okay - but since the shower is over 8' tall, and I'm tiling it up to the ceiling, won't I have that problem anyway, by virtue of the fact that I'm almost certain it will take a lot of time for me to work my way up?

Just so you know, I'm good at stuff, but it's my first tile attempt and I'm going to want to take my time doing it. So if, like drywall, I tape the corners all the way up in one swoop, I don't think I can get all the way up two walls with the tile before it dries...

And, I will need to let that bowing-fill dry too, right?

Also, don't I have to be taped and mudded before it gets the RedGuard anyway?

How do I get around all that? THANK YOU, Taran

Bud Cline 06-14-2011 07:40 PM

Okay, I forgot about the Redgard thing.

Here's an optional method and this is what I do as much as I hate to share it here.

Buy a can of 3M Spray Adhesive for drywall. That's what the label says.
Spray your seams and corners lightly.
Let the adhesive dry.
Apply your mesh tape. It already has adhesive on one side so pay attention cause once it is stuck, it's stuck. Strike the tape down firmly with a putty knife.
Apply the Redgard generously over the tape. Fill all the pin holes.
Let it dry. More pin holes will develop so paint it again.

Now you can install the additional Redgard in the fields.

Install the tile.

Taran7 06-14-2011 08:24 PM

okay, that sounds good -- what about jamming some thinset in the 1/8 inch gap Durock told me to leave, then do your treatment?

(I take it your spray is to make triple sure the tape isn't going anywhere?)

also, shouldn't I fill that bow and let it dry before the redgaurd too?

thanks for your time, Taran

Bud Cline 06-14-2011 08:52 PM

Fill the bow and let it dry and get it behind you.

The spray adhesive is to insure the tape will stay put after it is applied. Cement board is dusty and the adhesive that comes on the tape is NEVER enough. Be sure not to let the corners become radii, tuck the tape tight into the corners as you apply it.

I wouldn't worry about the small gaps. The waterproofing will cover them if you pay attention and be generous. Redgard is costly but if you skimp you have defeated the purpose of using it.:)

The 1/8" board-gap recommendation is intended for boards being installed on a floor. A wall is a different story.:)

Taran7 06-14-2011 11:03 PM

Man, I wouldn't have busted a vein in my forehead forcing a sheet up so I could get that 1/8 inch today if I had known that.

I am going to slather on the Redguard, believe me.

Thanks for your time, it helps a lot. --taran

mikeylikesit580 06-27-2011 08:13 PM

Thank you guys! I really enjoy reading all your posts trying to figure out how to do this all right!

Dr duerite 06-28-2011 01:30 PM

durock problem
yea now I till you.
before installing the durock check with a long straight level,laser and sqaure to make sure your walls are straight, sqaure and true. If they are not Use new 2x4 and sister them to the existing wall studs to protrude out to the high point and make the walls sqaure and true. your job will look like a new build when you are finished, and there will be no shimming needed.
If you use too much premixed thinset on the walls,you can count on it not drying in your life time.
But if you mix a bag and trowel it on the wall to fill a void it will set up, use fibergass mesh on the surface to give the premix thin set something to adhear to.
Dr Durite

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