Tile Surround for 1950's Crane Ceramic Tub - Edge Detail Best Practices?

[Steve_S]

Remodeling a bathroom and want to do a tile surround with the existing tub, which is a ceramic Crane tub installed in 1952. In addition to the ceramic aspect being somewhat unique, it is an undersized tub (26x53" or so) in a small bathroom... and there's not really space to change to a modern standard size tub anyway. (I *think* the tub is probably an Oxford model but not 100% sure--bathroom had a wall mount Oxford sink and Drexel toilet.)

My current inclination is to do a Kerdi membrane over drywall for the waterproofing of the surround, however am unclear on how best to transition the drywall/membrane/tile to the tub to most effectively seal everything.

The tub has a small (~3/8" H 3/8" W) lip on the three sides that would receive tile surround. Hopefully a couple pictures showing the setup will properly attach and show up with the post (FYI the insulation looks sloppy because it's not permanently installed yet--there's some weird framing from when this bathroom was added I still need to work out, but it's been crazy cold here the past couple days so just shoved insulation into cavities without trimming batts).

I'm also including a diagram of how I think maybe this should work... but would like advice if this is correct and what products are best/proper to seal the kerdi/drywall/tub interface (pink area - Kerdi fix?) and also between the bottom edge of the tile and the tub deck (green area - grout matching caulk? Silicone?).

I've looked through the Kerdi documentation some, but it seemed like instructions generally assumed you were working with a taller lip on a fiberglass tub... I want to make sure I'm doing this in a way that lasts and hopefully doesn't have moisture ingress problems in 5-10-30 years, so looking for advice from pros or anyone who has encountered a similar situation. I'm pretty handy, and have done some tile work, but am definitely not an expert... and I strongly suspect the devil is in the details when it comes to keeping water out.

If there is another method/system that is easier to make work than Kerdi in this scenario, I'm also open to alternative options--I haven't hung drywall or bought the Kerdi stuff yet.

[cx]

Welcome back, Steve.

Originally Posted by Steve

...but it's been crazy cold here the past couple days...

That sort of statement is a lot more meaningful if you have a geographic location in your User Profile and it's often helpful in responding to some types of questions.

I think the sheet-type bonded waterproof membrane (Kerdi, etc.) is one of the best ways to deal with that kind of tub application.

I would want as much of the membrane as possible bonded to as much of the tub as possible and Kerdi Fix or an equivalent is one of the best products to do that.

In the areas where you actually have the insufficient lip, I'd try to run the membrane down onto the tub as far as you possibly can without it showing under the tile edge. And I'd want to stop my wallboard at least an eighth-inch above the lip, giving me enough space for a tiny bit of a wedgie in the membrane to allow for movement. Bond the membrane to the wallboard with thinset mortar.

In the areas where you don't even have the hint of a tiling flange, I'd again try to get my membrane onto the tub as far as possible without it being visible under the tile lip. I'd likely make it a little long and expect to trim the edge with a razor blade after the tile was set.

I'd want that membrane to extend an absolute minimum of 2, preferably at least 3 inches beyond the front of the tub to waterproof the "tub leg" of tile down to the floor. I'd want to bond the membrane to the tub in that area as well.

Or you could do something else, of course.

The green in your drawing should be a flexible sealant, preferably color and texture matched to your grout. 100 percent silicone is the type most usually recommended for use in wet areas. I don't like making a complete seal in that area, but that's what the industry standards require.

My opinion; worth price charged.

[Snets]

Steve, check out THIS VIDEO from Schluter that addresses how to waterproof the wall/tub transition.

You pretty much have it right except it would be difficult to combine the Kerdi Fix and Kerdi membrane in that application, in my opinion. You will see in the video how they use Kerdi band over Fix and thinset to make the seal.

I will tell you from someone who has built two showers, one with membrane over drywall, and one with Kerdi Board, I would NEVER use membrane over drywall again. The board is WAY less work.

Schluter sells a kit with everything you will need to do a tub enclosure all in one box. I'm installing one in a couple of weeks at a friend's new tub. (shop around, prices vary a lot, I saved well over $100 below the HD price!)

That's cool combining that vintage, unique tub in a modern, waterproof installation!

[Steve_S]

Thanks!

Apologies for not including location in my profile... got it added--I'm in Iowa.

I think I prefer the idea of the membrane over the board for a few reasons:
1) With the membrane/band you can overlap everything in a way that makes sure water migrates out (like flashing a window bottom first, then sides, then top)
2) I don't know anywhere around that I can get get Kerdi board... HD/Lowe's show some stuff on their site, but don't seem to stock kerdi board at all in this region. Rolls of membrane are a bunch more practical to get shipped than board.
3) I'm not crazy about the idea of foam from a strength standpoint... especially since a lot of things in this house (built ~1913) are not standard 16" spacing required for the 1/2" Kerdi board... so somewhat likely I'd need to either add studs (which probably don't match dimensions of current lumber), or use thicker kerdi board rated to bridge wider spacing that would make the tile stick out from the drywall.

CX, is the attached close to what you're describing as far as 1/8" gap between drywall and lip on tub, sealant, tucking membrane?

I watched Schluter's video on installing the tubkit membrane product earlier last week before I tore things out, so at that time I didn't know if there was even a lip there at all. My diagram just shows a layer of orange for the kerdi, but I think following their instructions I'd actually end up using the band to bridge the gap and seal to the tub deck, then put big section of membrane over top of the band using thinset only--correct?

[cx]

3. You need the same stud spacing for your drywall or CBU on your shower walls as for the half-inch foam board, Steve.

Yes, that drawing is what I had in mind, but without the complete filling at the green part. You want a simple sealant joint between bottom of tile and tub.

There is no need to apply the Kerdi and KerdiBand in a shingle-like orientation. So long as you make a minimum of two inches of overlap, you can install the layers in any order. I would want to band the tub first, anyway, from a functional standpoint, but it doesn't matter at all.

My opinion; worth price charged.