Help! Shower bench waterproofing and moisture sandwich?! [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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12-15-2016, 02:50 PM
We're putting in a traditional wood framed shower with a bench. We've gotten the preslope and PVC liner installed. the plan was to paint the cbu with redgard after installation (no plastic behind the cbu). Currently we are in information overload about how to waterproof the bench. We were planning on applying PVC liner to the bench, going up the walls a few inches, doing the apprpriate corner treatments etc, then put down cbu (not screwing the seat piece.. instead, thinsetting/mortaring it down, and locking it in with the surrounding walls) then painting it all with redgard after testing the seams.

So... Is that too much of a "moisture sandwich"? If so, what do we do instead? And are we then worried about the sandwich of a few layers at the bottom of the cbu where there is pan liner behind?

Thanks for your advice!!

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12-15-2016, 07:36 PM
If the seat is framed with lumber, go ahead and cover the whole thing with CBU, overlapping the pan liner that's on the floor and up the walls 10-12 inches. Once the CBU is fastened down to the walls and seat, tape the CBU joints and Redgard to whole thing. No need for the pan liner on the seat. Make sure you get the Redgard the proper thickness. Also make sure you have a pitch on the top of the seat.

Make sure you notch the studs for the liner and don't nail CBU on the top and inside of the curb. Check out the "Shower construction info" thread in the liberry.

12-15-2016, 09:28 PM
Thank you! Yes after much reading, that is what we are leaning towards. Your input is very much appreciated!

What about the plan to paint all the cbu with redgard (albeit not as thick as on the seat)..? Still appropriate to do this with the traditional pan liner, since we weren't going to put a moisture barrier up behind the cbu? Do we need to worry about not painting the cbu that is overlapping the liner for that 10 inches on the bottom?

12-15-2016, 09:33 PM
Welcome, Jen. :)

If you don't install a moisture barrier behind your CBU wallboard, you must apply a direct bonded waterproofing membrane on the inside. Must. Don't be concerned with the waterproofing membrane overlapping the shower's receptor liner that extends up the walls a minimum of 3 inches above the shower curb.

The waterproofing material (RedGard in your case) must be of the thickness specified by the manufacturer. Everywhere. And please be careful, it's a whole lot thicker than you might guess. Best to get a wet film thickness gauge from your local paint store if you can't get one where you purchase your waterproofing.

My opinion; worth price charged.

12-16-2016, 10:22 AM
Great, thanks so much. We will sleep better knowing we are doing it right... ! There are so many opinions out there it is nice to have confirmation on our approach and advice on how to improve it. Hadn't thought of a thickness gauge so I'll definitely try to get one.

Btw... This forum is awesome... Lots of good stuff...!

05-24-2017, 04:31 AM
Share some pictures of your work.

You can waterproof the wooden benches using the liquid like hydroban or be using the sheet or board like kerdi. You can make the shower bench using the bricks and frame the top with a cement board. You can also use plywood for framing. Remember to include a slope for the bench in order to drain off the water. If you are using plywood for framing, use galvanized screws to securely anchor the plywood to the bench. Install the pan liner to waterproof the wood. Remember to install the backboard to overlap the lower pieces of the bench. Cover the shower bench using the tile.
You can also get the shower seats online or from the market. It is now sold as one of the bath and shower accessories (

05-24-2017, 11:21 AM
Anna, the thread's five months old and I expect the shower is well on its way to completion by now.