I have read lots of posts re tile preparation for a shower. Am I right in thinking:
Use conerete backer board on studs (inside wall) Tape joints with fibreglass tape made for concrete board & mud with modified acrylic thinset.
Cover all with kerdi & all will be well?
Thanks for any info.

Are you saying you installed a cement board and a Kerdi membrane? Bit of an over kill so yes all will be well. You could have done cement OR Kerdi over drywall and it would have been OK.

As they say... do it right the first time and you will only do it once

1)Preformed pan or 2)Kerdi drain/membrane tiled pan, or 3) site built pan with a pvc liner??

If 1 or 2, regular sheetrock is all you need, no cement board needed. Actually, SR is better in that proud screw heads in cement board can result in bump/bubbles under the kerdi. Larger panels for SR also means less seams and butting tapered edge to tapered edge of the sheetrock eliminates bumps where panels join. For those seams, I'll use backer tape and if I have some in the truck, rapid setting mortar in one coat to fill the recess of the tapers. You won't need to tape/thinset the inside corners with Kerdi, kerdi band is used in the inside corners and takes care of that with minimal material buildup. With both, you will need to make sure you make several slits through the facing on your insulation if it's an exterior wall or use unfaced insulation. Kerdi is the vapor barrier for those walls. If it's a preformed pan, you will need to seal the kerdi membrane to the pan with Kerdifix sealant. Yes, you want to use the $20/tube kerdi sealant for this. Also, if it's acrylic or fiberglass with glossy finish, place some masking tape just in front of where the kerdi will be bonded to the pan and scuff it with some 80 grit to roughen the gloss coat and give the sealant better grip to the pan.

If 3, skip the liner and buy additional kerdi and the kerdi drain. With the pvc liner type pan, you still have the bottom of the board sittinng in the setting bed of the pan and some wicking into the board will occur and be between the wall cavity and the Kerdi. Could take quite a while to dry out. You will need to use cement board in that case.

I didn't yet but all the info was what I needed.
Thank you all very much.

If you mean you have not done the work yet then pick one or the other approach and do not do over kill.

Also, don't forget to install moisture barrier over bare studs...

Also, don't forget to install moisture barrier over bare studs....


Under most common shower construction techniques with cement boards, yes, but with kerdi, the surface membrane is both water and vapor proof, which is why I included the step of either nullifying the facing on insulation or using unfaced.

With Kerdi or Nobleseal TS, since the membrane is both water and vapor proof, it leaves no question as to whether a moisture barrier is needed.

With trowel on liquid membranes, some need a vapor barrier behind them and some don't, depends upon the application and the perm rating of the membrane so when unfamiliar, check with the manufacturer. It's usually included in technical bulletins, but not listed at all on the bucket.

Which liquid membrane, trowel on, are you comfortable with Bljack?

Though laticrete's hydroban is my preferred, I use Redgard more frequently. Both are very good products and both are approved for use as a shower pan liner, replacing the need for the pvc liner and allowing the continuous application over the pan and then up the walls.