How to seal below concrete board sealed with RedGard
 

Hi,

I am remodeling my bathroom. I will be installing ceramic tiles in the shower stall walls, and using an Onyx shower base. I have already installed concrete board (HardiBacker) onto the studs, and plan to waterproof it with RedGard.

My question is this: since there is a 1/4" gap between the bottom of the concrete board and the lip of the shower pan, what should be done to waterproof that gap? I understand that there will be mortar there in back of the overhanging tiles, but I am concerned about water getting through the tiles and mortar.

Any advice is appreciated!

Thanks,
Dan

Caulk.

That 1/4" gap is to keep the cement board from wicking up moisture. When you tile, spread your thin-set mortar all the way down, but set your tiles up a bit using spacers. When the mortar is cured, run a small bead of silicone to seal between the tub and the tiles.

DO NOT use thinset in that gap.

Caulk that gap with siliconized or latex caulk and then use Redgard over the caulk. Regard will not stick to 100% silicone caulk. You DO NOT want moisture collecting in that crevice and it can if you stuff it with thinset.

Then after the tile is installed caulk that gap also. I wouldn't ramp those tiles either. There is no need for that and that would look really stupid. No reason to have those two or three tiles tilted/ramped.

Hello Bud,

I know this thread is old but i hope you can reply to it.

Can I use an Acrylic latex caulk plus silicone in this same situation posted earlier or does it have to be straight latex?

Hope you can still reply to this thread