Shower Tear-Out & Rebuild

[MesaTileworks]

Hi All,
I’m starting a new project with some tricky details that are a little outside my prior experience so starting a new thread here in hopes I can get some advice. This community has been so helpful, and I’m very grateful to the folks who share their time and expertise here!

Some friends have hired me to tear out and redo their shower. The original install must have been dodgy, because there were multiple problems, including cracked grout, loose tiles, lack of proper drainage in the pan, niche, and bench, and so on.

I’ve almost finished the demo and am getting ready to rebuild the bench and curb, install a new niche, and repair or replace the knee-wall (maybe half-wall or pony wall is the proper term?) in preparation for putting up CBU, waterproofing, and tile. My friends would like essentially the same size and layout as the original—see pics below; before and after demo.

A few questions as I do framing for the bench, half-wall, and curb:

1) Should the bench be reinforced by putting a layer of 1/2” plywood between the framing and the CBU? Or is CBU sufficient? (I’m planning on using Durock and waterproofing with Aquadefense).

2) Same question for the half-wall, which has to support the weight of the glass that will be installed and be stable and rigid enough for tile. (See photo of original framing for this area—I’m wondering if I should install some cross braces to prevent moment, or whether the fact that the branch will tie the half-wall to the side wall is sufficient reinforcement?)

3) I’ve not decided yet whether to use a Schluter curb or build one with 2X4s and CBU. I read a recommendation somewhere to avoid using pressure-treated lumber for a shower curb because the wood is basically wet from the manufacturing process, and more liable to warp or twist as is ages and dries out. Does this jive with anyone’s experience? Is it better to use standard untreated wood for a shower curb? Is 2X4 covered in Durock, waterproofed with a membrane an acceptable way to build a curb?

I’m sure more questions will come up but that’s what I’ve got for now. Thanks in advance for any insights.

-matt


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[Davy]

Looks like the old shower has a Schluter drain, do you plan to keep it and go back with Kerdi? If so, go ahead and use Kerdi on the walls too.

I think it's best to stiffen the pony wall by anchoring the end 2x4 into the floor framing (the 2x4 that's white in your picture). I would double up that 2x4 as well.

[jadnashua]

Don't know what the budget is, and you may or may not be getting paid much in labor, if at all for a friend, but I'd consider going back and using Kerdi. You could use Kerdiboard for the walls, and to actually build the curb, pony wall and niche and eliminate most of the wood in the shower. Schluter does sell prefab curbs, niches, and benches, but, you can build them, cover with a suitable material, then cover with Kerdi.

I'm not a fan of trying to use a painted, liquid applied waterproofing.

Any shower, done according to one of the TCNA guidelines and manufacturer's instructions would not have failed the way you described. Not terribly hard, but very detail oriented. IT takes some understanding and skill, but it's not rocket science. A little artistic talent can help it look nice, but that's not required to have a functional shower.

[MesaTileworks]

Originally Posted by jadnashua

...cover with a suitable material, then cover with Kerdi.

I'm not a fan of trying to use a painted, liquid applied waterproofing.

.

[MesaTileworks]

@jadnadhua, when you say “cover with a suitable material,” what would you put between the framing and the Kerdi board? I had thought of putting plywood over the bench framing, then Durock, then waterproofing membrane.

Curious too about anyone’s thoughts of doing a Kerdi pan with Durock walls, putting a liquid membrane on the walls, and the sealing the bottom plane intersection and the pan with Kerdi. I realize this mixed materials approach might not be standard. Just wondering if this is a thing anyone does? Any success/horror stories?

Apart from saving my friends some money (the Schluter materials tend to be pricey), I like the rigidity and strength of Durock, but I’m still in the planning phase so could go different directions.

[MesaTileworks]

On another note: on removing the old pan, I’ve noticed that underneath it is some 1/8” plywood on top of the subfloor. I’m thinking I should either remove it or place additional screws in it, as it seems to be inadequately screwed down.

Any thoughts on whether it needs to be removed or just secured? (I’d fill the gap shown here with mud of some sort before laying the new pan.)

[MesaTileworks]

Related to this last question: I am not sure about the joist size and spacing and without taking up the subfloor it’s difficult to say for sure. Would it be a better idea to screw down an additional layer of plywood before installing a Schluter shower pan or is a standard half-inch plywood sufficient?

[MesaTileworks]

Update: I decided to remove the 1/8” ply, as it seemed dodgy. Now my next question on that front is whether the existing 5/8” plywood subfloor (looks to be 16” OC but hard to tell for sure) is sufficient substrate for a Schluter pan, or whether I should put down an additional layer of plywood (I have some 3/4” on hand if that’s not ridiculous overkill).

Sorry for all the questions, but thanks for any advice!

[MesaTileworks]

Have determined that the subfloor is 3/4” ply over 2X12s, 16” OC. I’ve done a few searches but so far unable to verify if this is sufficient substrate for a Schluter pan. Anyone know for sure?

[cx]

Schluter knows for sure, Matt. Did you consult their website?

Personally, I'm quite sure they approve a nominal 3/4" plywood over 16" joist centers, but you really shouldn't take the word of someone you don't know who you found online when the information is readily available from the manufacturer. Of course their recommendation would be based upon new, undamaged material, properly installed.

Without knowing the length of your joists we can't help with the evaluation of the joist structure, which would be significant if you plan to tile the floor of that bathroom.

You were certainly correct in removing a 1/8th" plywood from the subfloor.

My opinion; worth price charged.

[MesaTileworks]

Thanks, CX. I’ve been combing through data sheets on Schluter’s website but with the number of products available, it’s proving difficult so far to find the particular info that relates to minimum requirements for their shower pans.

Any thoughts on whether 3/4” ply with 1/2” Durock is sufficient construction for a 48” wide shower bench? (assuming that the framing is done correctly of course.)

[cx]

Matt, I just downloaded the Schluter Kerdi Handbook for about the brazilionth time and I gotta say I did not find a subfloor specification for installation of their foam shower tray. Closest I could find was that it needed to be clean OSB, plywood, or concrete. Given that lack, one would be forced to rely upon residential building code as a minimum default and your plywood would exceed that requirement. I wish you'd contact the Mother Ship (800-472-4588) and ask them where to find that information. 'Specially since they make a point of telling you that their written instructions "shall have precedence over" any and all other industry standard guidelines. And please tell us what the response might be.

Durock manufacturer claims no structural properties for the material. For the front of the bench the framing would need to be that required for wall framing. For the top I would think the framing requirement and backing would be the same as for a floor application.

My opinion; worth price charged.

[MesaTileworks]

Alrighty, will do. Thank you, sir!


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[MesaTileworks]

Welp, the Schluter rep said they don’t have a specification for required subfloor for their shower pan and just to follow the local building codes. Given that they have such specific requirements for their other products and that local code requirements aren’t going to take into account the specific properties of a product like a Schluter shower pan, this is odd and kind of unhelpful but oh well... Guess I will be looking up that building code.

[Tiger Mountain Tile Inc]

Originally Posted by MesaTileworks

Curious too about anyone’s thoughts of doing a Kerdi pan with Durock walls, putting a liquid membrane on the walls, and the sealing the bottom plane intersection and the pan with Kerdi. I realize this mixed materials approach might not be standard. Just wondering if this is a thing anyone does?

So, Schluter obviously won't care for this approach but it can be done. In fact, if you used the Laticrete version of the products they would offer a warranty for it.

The pan is the big thing. It's always nice to have a sheet membrane on the shower pan.

Also, that half wall could be stiffened up quite a bit. You're supposed to have 2x6 blocking around the bottom perimeter of the shower. You could also add it to the top. Plus, an additional stud on the end would do you some good. If you screw all of those components in then you'll make that wall a lot more sturdy.