Shower from the 60's

[HooKooDoo Ku]

What Kind of Cement
Regardless of the curb for the moment...

Assume I'm going to move forward with only replacing the shower pan...

When it comes time to match the thickness of the current shower wall, what sort of cement should I be using to build up a 1"+ base layer that the tile will be applied to?


Notes
I'm used to working with thin-set, but as that name implies, that's only designed for thin layers, not building up a 1" layer.

From what I recall from memory reading thru this forum of the years (mainly 10 years ago when I was finishing in a basement bathroom) about the only thing that was ever talked about when it came to walls in a shower was:
1. CBU with plastic behind it, or a waterproof coating on top
2. Drywall covered with Schluter's waterproof system

I don't recall much talk of any sort of 1"+ layer of cement on top of a wire mesh.

But then again I still need to DEMO one more row of Tile inside the shower to get completely above the old shower pan and see how that section of the wall was constructed.

[cx]

Joseph, cement, usually Portland cement, is a component, the binder, in mixes for various mortars and concrete.

For walls, the mortar is usually sand, cement, and lime. Not uncommon for it to be 1" or more thick. For floors, including shower floors, the mix is usually just sand and cement. In days of old, prior to thinset mortars, such wall mortar, or "fat-mud" over roofing felt and expanded metal lath or "chicken wire" was the way shower walls were done.

When you ask "what kind of cement," I'd say it's usually a Portland cement of Type I or II, frequently bagged as just that, "Type I/II." But I think you're actually wanting to know about what kind of mortar mix to use for your various applications. If you'll look in our Liberry under the Shower Construction thread, you'll find posts showing the various mixes and how to make them from bagged materials available at your local home center.

As to your plan to make your new shower receptor without a pre-slope, I look at the heading of your first post on this thread and ask, "Why would he want to do that again?"

I'm having some difficulty matching your descriptions with your photos, but if you're saying you don't have sufficient vertical space for a pre-slope, waterproof liner, and top mortar bed, I think you need to think about changing to a bonding-flange drain and a direct bonded waterproof membrane type of receptor construction. I don't see a reason to try to cobble together a traditional receptor if it's going to mean doing so without the required pre-slope.

I'm keeping in mind that trying to replace only the receptor of a failed shower is usually considered to be a temporary patch until the whole shower can be replaced, but you'd still want to make a proper receptor of some sort, yes?

My opinion; worth price charged.

[HooKooDoo Ku]

Originally Posted by CX

For walls, the mortar is usually sand, cement, and lime. Not uncommon for it to be 1" or more thick. For floors, including shower floors, the mix is usually just sand and cement. In days of old, prior to thinset mortars, such wall mortar, or "fat-mud" over roofing felt and expanded metal lath or "chicken wire" was the way shower walls were done.

That's pretty much the exact construction of this shower.
Except the "chicken wire" looks to be galvanized steel stucco netting with mesh holes much smaller than the 1" mesh holes you see in classic chicken wire fencing.

Originally Posted by CX

When you ask "what kind of cement,"

Sounds like my answer is "fat-mud".
I'll find and read over those Liberry articles you referenced.

Originally Posted by CX

if you're saying you don't have sufficient vertical space for a pre-slope, waterproof liner, and top mortar bed, I think you need to think about changing to a bonding-flange drain and a direct bonded waterproof membrane type of receptor construction.

Yeah, the construction only has about 6" from the top of the floor joist to the top of the original curb.

So I guess you're basically talking about using the Kerdi system.
Specifically just laydown a preslope and then use a Kerdi drain and kerdi membrane on the preslope.

I'd still need the fat-mud on top of the membrane to build up the thickness for the new tile to line-up with the new tile.

The down side is going to be the cost. $100 for the drain and $120 for the membrane. But the plus side is that it sounds like kerdi is easier to install than making all those folds in a PVC liner.

I'll do some more research and do some more thinking/planning this week. I don't expect to actually do anymore work until this weekend.

[cx]

Originally Posted by Joseph

So I guess you're basically talking about using the Kerdi system.
Specifically just laydown a preslope and then use a Kerdi drain and kerdi membrane on the preslope.

No, Kerdi is just one example of the type of receptor construction I'm suggesting. There are many others.

Originally Posted by Joseph

I'd still need the fat-mud on top of the membrane to build up the thickness for the new tile to line-up with the new tile.

One does not use a top mortar bed with the direct bonded waterproofing systems. Direct bonded means you bond your tile directly to the membrane. If you want the additional height, you can either go back to a clamping drain and traditional construct, or make your sloped bed high enough before installing the waterproof membrane. There is no pre-slope with that type of waterproofing system.

Originally Posted by Joseph

But the plus side is that it sounds like kerdi is easier to install than making all those folds in a PVC liner.

I would certainly not say that. The installations are different, but if I had to say one was easier, I would say the traditional liner. Both require attention to detail to work properly.

My opinion; worth price charged.

[HooKooDoo Ku]

Originally Posted by CX

One does not use a top mortar bed with the direct bonded waterproofing systems. Direct bonded means you bond your tile directly to the membrane. If you want the additional height...

Hmm... That makes things interesting...

"Height" isn't an issue... it's width (wall thickness).

Existing wall has about 1" of fat-mud between the waterproof layer and the tile. It would seem strange if the water proof layer of the shower pan was 1" in front of the old waterproof layer.

This would be the first thing I can think of to try to use surface membrane on the walls.

The idea would be for plywood to act as both a backer and something to thicken the wall. The membrane would go up the backer and then on top of the backer to get as close to the existing waterproof layer as possible. Or perhaps better would be some slope towards the exiting waterproof layer.

[HooKooDoo Ku]

I finally have a floor...

So I've decided to commit to the sin of only replacing the shower pan, but I'll build it with the proper preslope.

Good Plan for Building Shower Pan?
Layers:
1. 3/4" Plywood sub-floor
2. Sheet of plastic (to avoid soaking up moisture from mud bed
3. Galvanized steel stucco mesh
4. Mud bed (1-1/2" min with 1/4"/1" slope)
5. Kerdie waterproof system (drain and fabric)
6. Tile

Specific Questions
1. Is it better to have the stucco mesh suspended in the middle of the mud bed?... Say lay down a 1/2" layer of mud, then the mesh, then the rest of the mud?
2. Is there a "standard" way of leaving a hole in the mud bed so that it's just the right size for the Kerdie drain assembly to fit thru? I know I'll be able to jerryrig something, but I didn't know if there was some industry trick, of something you use for that that comes with a Kerdie Drain kit.
3. Any other suggestions for altering the above plans?

[cx]

Originally Posted by Joseph

So I've decided to commit to the sin of only replacing the shower pan, but I'll build it with the proper preslope.

Joseph, the type of shower receptor you're no proposing does not use a pre-slope. It has only a single sloped mortar floor.

1. OK, so long as your joist spacing is no more than 16" on center.

3. Stucco mesh, while an acceptable substitute for expanded metal lath in wall mud applications, is not an acceptable substitute for deck mud over expanded metal lath. Nor is it acceptable if you are attempting to make your shower floor a reinforced mortar bed. For that you require welded wire mesh in various sizes, the 2"X2" being the most common.

Originally Posted by Joseph

4. (1-1/2" min with 1/4"/1" slope)

Not sure if that's a typo, but the minimum required slope is 1/4-inch vertical to 12 inches horizontal. A 2 percent slope.

1. See #3 in your Plans list.

2. You install the drain at the same time as you're making the sloped mortar floor when using the Kerdi system. I really hope you'll take some time to view some of the Schluter videos showing the installation of their products. They have some very good ones on their website that should make you more comfortable with your installation.

3. I really don't see how you intent to even attempt to tie your old wall waterproofing with your new receptor. Putting that plywood in the gap you've made in the bottom of your walls looks to me as though any moisture that collects on the moisture barrier behind your mortar walls is gonna be directed down onto the end grain of your plywood. Granted, the mortar wall won't allow as much water through it as would a CBU wall, but there will still be some. I would much rather see you use something cementitious to fill that void you've made. Schluter would be happier too, as they do not recommend bonding Kerdi to any kind of wood.

My opinion; worth price charged.

[HooKooDoo Ku]

Thanks for the reply CX... here's a follow up to your replies.

Pre-Slope
Sorry... guess for this construction, I am using the wrong terminology.
I'm still thinking of it as a "pre-slope" under the water proof layer.
But yeah, I understand there's only one mortar bed, and that's why it will need to be thicker than the thinnest you can make a true pre-slope.
Given nothing was said to the contrary, I assume that means a 1-1/2" thick mortar bed is good enough over plywood.

Floor Joist
The floor joist spacing is about 13"... after adding some sister joist for various reasons.

Mesh
Based on Davy's picture (Post #7 on Page 1), I thought he was using Stucco Netting like this found at Lowe's.

I'm having problems looking online to source a 2" x 2" mesh. Looking at what Home Depot and Lowe's has to offer, they basically only have 42" x 7' sheets with 6" spacing. That almost sounds too big to help much in a 33x33 floor. If I'm limited to 6x6 mesh (for the simplicity of sourcing) could I put a second layer of mesh over the first, offset by a half spacing making sort of a net 3" spacing?

Slope Typo
I was trying to say that I'd start with a minimum 1-1/2" mortar bed, and slope it 1/4" thicker per foot towards the walls.

Drain
Found the instructions how you start your mortar bed by installing the Kerdie drain in some mud and then build your mortar bed out from there.

Plywood along the Wall
The plywood along the wall is supposed to fill a couple of purposes...
1. Wall support: Two sole plates have major rotting leaving two studs unsupported (except from above by the wall attached to it). So I want to use the plywood to help tie the studs back to the floor.
2. Blocking: I'll need some blocking... I need something over the face of the rotted spots of the sole plate.
3. Spacer: I'll need something to help fill that 1" to 1-1/2" space from the studs to the back side of the existing tile.

Originally Posted by CX

I really don't see how you intent to even attempt to tie your old wall waterproofing with your new receptor.

1. I don't... I thought that was the general understanding of ever replacing just a shower pan.
2. This job only needs to last for a few years.

Originally Posted by CX

any moisture that collects on the moisture barrier behind your mortar walls is gonna be directed down onto the end grain of your plywood...
...I would much rather see you use something cementitious to fill that void you've made. Schluter would be happier too, as they do not recommend bonding Kerdi to any kind of wood.

Good points.
Perhaps there will be enough spacing that I can add a layer of 1/4" Hardiebacker.
To mitigate water getting absorbed by the end-grain of the wood, I could add a flap of Kerdie. Staple it to the back of the plywood before installation, and make sure it's wide enough create a 2" overlap into the shower pan.


Again, thanks CX for the great feedback.

[cx]

Originally Posted by Joseph

2. This job only needs to last for a few years.

Well, I think you're on the right track there, Joseph!

The "fix" could result in more damage to the framing over those few years, though. You should keep that in mind while saving up dinero for the shower replacement, eh?

You don't need to create a "reinforced mortar bed" for your shower floor application so long as the floor is under 65 square feet. You should, though, staple cleavage membrane and expanded metal lath to your subfloor before placing that sloped mortar bed.

My opinion; worth price charged.

[HooKooDoo Ku]

Originally Posted by CX

You don't need to create a "reinforced mortar bed" for your shower floor application so long as the floor is under 65 square feet. You should, though, staple cleavage membrane and expanded metal lath to your subfloor before placing that sloped mortar bed.

There's been a change in plans for the mortar bed.

I came across a good deal on a 38"x38" Schluter Kerdi-Shower tray and decided the extra cost was worth not having to deal with the mortar bed.

So the next question is what would be the recommended floor under this shower tray?

The new floor is so far made of two pieces of 3/4" plywood with the seam running perpendicular to the floor joist. The thinness of the tray allows room to add an additional layers to the floor, so I figured I would at least add a 1/2" layer of plywood with that seam running parallel to the joists.

[cx]

Joseph, I can't tell by your description in what orientation you have your current subfloor. But ALL layers of structural subflooring must be oriented with the strength axis perpendicular to the joists.

My opinion; worth price charged.

[HooKooDoo Ku]

I didn't specifically think about the strength axis... but it sounds like I got lucky.

I started with a 24"x72" piece of scrap plywood. I created the floor by cutting a 24"x31" panel and a 7"x31" panel, laying the long dimensions perpendicular to the joist.

According to an article I found with a google search written by the 'Structural Building Components Association', the strength axis of plywood is generally along the long dimension (of the original sheet).

So it would seem that I've got the 1st layer laid correctly.

But I now get what you (CX) are saying... If I add a second layer, I still need to run the plywood in the same direction... I just need to make sure the joints don't overlap.

[cx]

Especially with those narrow pieces of subflooring, which, I presume, had not T&G edges and those edges were not blocked from below. That, if correct, would make not a very good subfloor, even for a shower.

My opinion; worth price charged.

[HooKooDoo Ku]

Edges are not T&G.

But I do have blocking such that the entire perimeter provides a supporting surface.

I've not installed it yet, but considered adding blocking under any joint.



I guess an alternate plan would be to get a sheet of OSB T&G for the base layer.

[HooKooDoo Ku]

There has been a Change of Plans

After adding the sister joists, there just wasn't any room to work from below, and it was proving impossible to carefully demo one more bottom row of tile from below.

Demo alone is likely going to be two more weekends.