Shower Tear-Out & Rebuild

[MesaTileworks]

Hi Tiger Mountain,
Thanks for the info. That’s pretty much what I figured in terms of the membrane/waterproofing. I didn’t know about Schluter offering a warranty in a Laticrete junction, that’s interesting.

Don’t suppose you have a link to something showing the details of the 2X6 situation you describe? (Diagram, photo, video, etc?) I don’t know that I’ve encountered that framing method and I’d like to check it out. Definitely want to make sure the knee-wall is as sturdy as possible. It will be tied into the framing for the bench (meaning it’s connected to the opposite wall), so hopefully that will provide some extra rigidity.

[BIGPHIL]

Matt,

I believe the blocking at the bottom of the wall, like in this picture, is what's James was referring to (not my work...just found a pic on the interwebs).

[MesaTileworks]

Interesting. So in the photo, what is the purpose of the 2X6 blocks? Are they a nailer for the bottom of the CBU? Do they provide a surface to prevent the pan mud from spilling over into the wall cavity? I can see how they might provide additional dimensional stability for a pony wall.

In an application like what’s pictured here, would you usually instal the mud pan first or the CBU?

[BIGPHIL]

The blocking serves several purposes. It'll add form support for the mud beds and pan liner (if doing a traditional mud bed install) as well as add support backing for the CBU.

Originally Posted by mesatileworks

Are they a nailer for the bottom of the CBU?

NO fasteners should penetrate any part of the framing that is below 3" above the top of the curb in that type of an install.

Originally Posted by mesatileworks

In an application like what’s pictured here, would you usually instal the mud pan first or the CBU?

Embedding a real cement board, like Durock, in the final mud bed is just fine. Fiber cement boards like Hardie Backer shouldn't be embedded.

[MesaTileworks]

Gotcha. That makes sense, thanks!

[Davy]

It's also a good idea to notch the studs about 1/8 or so deep behind the pan liner. This will recess the liner back a little and keep the folds from bulging the cement board out at the bottom of the walls.

The blocking is usually set back flush with the notches.

[MesaTileworks]

Going with a Kerdi pan, so no pan liner, but is there anything similar I should do to accommodate the build-up thickness of corners plus Kerdi band?

[MesaTileworks]

Having removed the weird layer of 1/8” ply from the subfloor and dry-fit the Schluter pan, it’s become apparent that the floor is out-of level to the extent that there won’t be sufficient slope (I’ve got about 1/8” of fall per foot towards the drain on the downhill side, instead of the 1/4” that I understand code requires).

I’m researching ways to level the area. It’s a 4’x4’ square that is about 1/4” lower along one side. Also slightly concave in the middle. Would a self-leveler or some kind of feathering and patching mortar be a better product for this kind of application?

[cx]

Just one of the reasons I don't favor those foam shower trays, Matt.

Easiest and best fix would be to abandon the foam tray, lay down some poly sheeting or roofing felt, staple down some expanded metal lath, and build a properly sloped floor using deck mud. It'll allow you to have a level perimeter, a proper slope to drain, a perfect match for the drain location, and a more solid floor regardless the lack of level in the subfloor structure.

You can, of course, use a leveling product to prepare the floor for that foam tray if you want.

My opinion; worth price charged.

[Tool Guy - Kg]

Another vote to alter your plans to a mud pan. Most everyone is nervous the first time they try, but it really is just like working with damp beach sand. Between setting a level perimeter and a few different lengths of screed sticks to reach the drain, it’s not too bad.

[MesaTileworks]

The homeowner prefers the idea of sticking with the Schluter pan and anyhow I’m not sure that we could return it at this point. Our local tile shop is recommending a layer of Laticrete NXT Level. Anyone use this before? Apparently you prime the subfloor and then mix up this stuff pretty loose and pour it and work it flat.

[cx]

Originally Posted by Matt

The homeowner prefers the idea of sticking with the Schluter pan...

What would be their reasoning for that, Matt?

There is no advantage at all to the use of those foam trays except to the installer when the shower footprint is designed for the foam tray to perfectly fit the footprint and the drain location on a perfectly flat floor. No advantage at all for a paying customer.

The mud bed provides a much more solid floor that always fits the footprint and drain location perfectly, requires no leveling of the subfloor, has a level perimeter, and has the code required slope. The materials are dirt cheap and I'll wager even paying a skilled operator to install the mud bed would still beat the price of the foam tray.

Better for the customer all around and, I submit, better for the installer in most residential applications.

My opinion; worth price charged.

[MesaTileworks]

Originally Posted by BIGPHIL

NO fasteners should penetrate any part of the framing that is below 3" above the top of the curb in that type of an install.

Embedding a real cement board, like Durock, in the final mud bed is just fine. Fiber cement boards like Hardie Backer shouldn't be embedded.

The 3” rule for fasteners is to prevent the pan liner from being punctured, yes?

I think I’ve read elsewhere on this site about the possibility of using a traditional mud pan with a Kerdi drain, and waterproof the pan with Kerdi mat? In this instance, the Kerdi would waterproof the seam where the mud bed meets the Durock, and the 3” rule would no longer apply?

[cx]

Matt, the rule for installing traditional liners requires the liner to rise a minimum of 6" up the wall or 3" above the curb, whichever it higher. The fastener placement is a bit arguable, but usually accepted in the top of the liner, but no lower than 2" above the curb. And one set of rules allows them as low as 1" above the curb. The important consideration is that water can fill the shower receptor to overflowing without ever reaching the level of the mechanical fasteners.

And you're correct that with a direct bonded waterproofing membrane receptor the point is moot because all the wallboard fasteners are completely covered by the waterproofing membrane.

My opinion; worth price charged.

[MesaTileworks]

Related: do folks generally screw Durock to the top plate, or just a vertical row of screws along each stud?