Curved Wall Shower

[travellingman]

First, happy new year and a big thanks to all of you out there. Thanks to your top notch advice, I've just successfully laid down the preslope deck mud for my basement reno's shower. The project is on the 5 year plan and the end is in sight! My research here has also illuminated a possible boo boo - I seek your collective wisdom.

The shower is 42"x50" with one curved corner that has a 21" inside radius. Some time ago I installed Durock on the flat wall surfaces and two layers of 1/4" plywood on the curved wall surface - all down to about 18" from subfloor level. This week I installed an older style 2 part clamping drain (i.e. not a Kerdi drain), a fracture mat, a bit of lath, mixed up some deck mud and did the preslope.

The plan here on out was to install a CPE liner, add the top of the drain, bring the wall sheathing down to within 1/4" inch from the liner, tape the walls with fiberglass tape and thinset (even the plywood), waterproof the walls with a liquid membrane product (BlueSeal), and install the top layer of deck mud.

Now I'm thinking I should've come here two years ago before I started on the walls. Correct me if I'm wrong, but I realize now that plywood right to the bottom seems to open the potential for moisture wicking, expanding wood, and general mayhem - even with the waterproofing. If I had come here much earlier, I'd have learned about PermaBase Flex and used it for the corner to begin with.

I suppose I could rip out the plywood and completely redo the corner with the PermaBase Flex, buuuut....do you think that it would be OK for me to finish the bottom of the corner with the PermaBase Flex while leaving the plywood alone? I can't see a downside to doing this - with 18 inches of flexible concrete board at the bottom it appears there is no exposure to moisture for the plywood (unless the liquid waterproof membrane fails).

Cheers!
Kent

[Deckert]

I can't say with certainty your plan will work or fail. All I can tell you is what I would do. I would remove the plywood, mud that radius corner, and use a surface applied liquid with divot method for the drain.

I don't know what BlueSeal is so can't tell you if that is good for this application. Also, you mentioned a "fracture mat"....whats the story on that, who makes it, etc?

[Brian in San Diego]

Kent,

I'm with Brannigan on this. You don't want 1/4" plywood as your only surface for waterproofing and applying tile. There's no reason why you couldn't put the flexible Permabase over the plywood (unless I'm missing something). Maybe a couple of pitchers would help.

I agree with Brannigan regarding the divot drain. I am having trouble getting my head around how you attach a liner to a curved wall but maybe it's done all the time. I would think the divot method with a liquid membrane would do the trick. If you haven't already done so you may want to take a look at the "unconventional" shower thread in the Pro's Hangout. I say "unconventional" because it may not be something we would recommend to DIYers. But all DIYers are not created equal and if you understand the theory and follow the methodology then it may be something to consider in your case.

I'm making the assumption that you planned on waterproofing the surface of the shower and there isn't any waterproofing behind the durock and plywood, right?

Kent, could you go to the User CP tab in the dark blue toolbar above and add your name to your signature line?

Brian

[travellingman]

Thanks for the pointer to the divot method. I hadn't heard of it, but I'll begin my research on it immediately to see if it might be something I'm up for.

Thanks also for the idea of just putting the PermaBase Flex on top of the plywood and adjacent Durock (after furring out the studs on the currently exposed bottom 18"). That is certainly doable and has the benefit of leaving a nice space for the liner folds on the curve.

The "fracture mat" is just a piece of thick poly underneath the preslope, the Harry Dunbar article in the Liberry calls it a slipsheet. Somewhere I heard it called a "fracture mat" and I kinda liked that term

The BlueSeal stuff is a surface applied liquid, very similar to RedGuard. I could also go with RedGuard as I happened to find a store that carries it the other day. There is no waterproofing of any kind behind the wall sheathing ... the idea is to apply the BlueSeal on the walls as per manufacturer's instructions, then thinset the tiles on the BlueSeal.

Just to clarify, the 1/4" plywood is doubled up to a total of 1/2" with a bazillion screws holding it on the studs (which are 6" apart). I'm pretty sure it is solid enough to carry the tile. The thinset will not be applied directly to the plywood, it'll be applied to the BlueSeal.

My camera died on me so I'll have to try to borrow something to get a pic.

[Brian in San Diego]

Kent,

I have heard of Blue Seal but have never heard it used in a shower application. From their website there is no mention that it can be used to waterproof a shower nor tile over it. I would stick with the ones approved for shower applications over approved substrates. The choice around here seems to by Laticrete's new offering, HydroBan. Many posts about it over in the pro's hangout.

Brian

[travellingman]

Brian, I've scoured the BlueSeal literature and web site too. They don't talk a lot about it, but there are a few clues:

"Not for use as a wearing surface. Membrane must be covered with tile or other protective surface."

"Install the tile over the membrane ..."

"Q: Could Blue Seal™ Flooring Membrane, be applied on the interior walls?
A: Blue Seal™ Flooring Membrane, can be applied to interior wall, shower walls and shower pans as a liner. Blue Seal™ Flooring Membrane should not be used on interior perimeter walls."

I'll contact the BlueSeal manufacturer to make sure the above wasn't some marketing intern getting out of hand with the literature . I'll report back what I find.

I've been scouring the pro's section learning about divots and hydroban etc etc. Had no idea there were so many different products out there. I'll see if I can find suppliers in these parts.

[custombuilt]

Use kerdi or hydroban....these are proven products. Forget the blueseal.

[travellingman]

I thought I might be past the point of no return wrt to Kerdi since I didn't use a Kerdi drain. Can Kerdi be used on walls only, with a traditional PVC liner type pan down below?

[Deckert]

I'd either use the whole Kerdi system or skip the Kerdi altogether. The curved wall makes this a natural for a liquid in my opinion.