How to determine if a shower pan was intalled [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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05-21-2006, 08:21 PM
While remodelling our shower I removed all the tile and drywall to which it was attached. The floor tile appears to have been installed directly on the concrete subfloor. How can I determine if this is the case or if a shower pan was installed and covered with mortar?

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05-21-2006, 08:26 PM
Welcome jw. :) A properly installed pan will turn up the walls at least 6 inches, really needs to be 8-12 inches. It will also lap over the curb. Have you found anything in these areas?

05-21-2006, 08:28 PM
Depending on location and age, the shower pan should contain a liner made of synthetic rubber, copper, or lead. The pan material should come up the walls to a height of several inches above the curb.

Do you see the pan material at the bottom of the walls?

Oops, I forgot. In California, shower pans are often hot-mopped with layer of roofing felt and tar, just like flat roofs.

05-23-2006, 06:26 PM
Thanks. The house was built in the mid 1980s. There is not really a curb on the shower; it has a sunken floor approximately 3 inches below the level of the bathroom floor. I have removed all the tile on the floor and the tile and drywall on the walls of the shower and there was no sign of a liner of any type. Which makes me wonder if it was ever installed. Assuming one was not installed, how would I go about putting one in. If I lay one on the current concrete floor, then fill with 1.5 inches of mud, that only leaves me with a 1.5 inch curb which the thickness of the tile would reduce even further. What is the recommeded curb height for showers?

05-23-2006, 08:02 PM
I think since you are on a concrete slab already, you can skip the mud layer on top of the liner. That is for wooden people.

I could be wrong. Keep posted to see if anyone contradicts me. If they do, they are probably right. I don't build showers for a living.

Hope this helps, Cain.

05-23-2006, 08:04 PM
First of all, check out the shower construction thread in the liberry, lots of good info there.

Some guys don't think a shower needs a pan if it's sunken. Around here most of us think it's a good idea to have a liner since concrete isn't waterproof and it's a matter of time till the slab gets saturated around the shower, especially if the weepholes in the drain are clogged.

Sounds like you could add one 2x4 for the curb. This will give you a small curb and give you something to attach the liner to. It will build up to 2-2 1/4 inches when the tile and mud are applied on the curb. I like the inside curb height from the finished shower floor to be 3 1/2 to 5 inches, wouldn't go less than 3 inches. :)

I think David means the preslope under the liner. You can skip it if the concrete already has a 1/4 inch fall per ft.

05-23-2006, 08:22 PM
if you dont use a liner, at the very least use redguard or hydro guard.

05-24-2006, 09:28 AM

When I answered your question, I expected you would put a liner in. Do that. Kerdi is thin. Paint-on liners are thin too. These are like what Zaritile mentioned above. They are considered liners too. Other liners are thicker, made of CPE or PVC ("rubber").

What I really said was only this: Don't put the 1.5" of mud you were referring to, if you do go ahead and build your own shower pan. You don't need more concrete as one might if one had a wooden subfloor. That would be useful as a floor stiffener, but your concrete floor is as stiff as it will ever be. By removing that 1.5" thick layer, you will get all the curb height you want.

It is possible to skip the Deck Mud layer when on a concrete slab. You can make a shower drain slope starting with zero extra height. So instead of trying to reduce the Deck Mud height, you can eliminate it altogether! That is not in the Liberry. As far as I know. And I don't read it every day. And neither do all the experts who refer to it.

I find the information available here in JBF is good for wooden structures. There is very little consistent or coherent information about how to proceed if you already have a concrete slab floor, either in the Library or in the Advice Forums. Perhaps I'll just have to write the missing information up and submit it. Even tho I have no epxerience. :D

05-27-2006, 10:23 AM
If I use kerdi, can I just replace my current drain with a kerdi drain and attach the kerdi membrane directly to the concrete floor? Also, if I am using backerboard on the walls, do I need to cover the entire walls with kerdi?

05-27-2006, 11:36 AM
Hi jw, the floor needs to be in purty good shape before putting down the Kerdi since your finish floor will follow it. It should be level around the walls with 1/4 inch fall per ft toward the drain. The concrete normally isn't like this so we put down a mud bed of dry pack under the Kerdi first. Dry pack should be bonded to the slab with a slurry of thinset, it's easy to shape and get the correct pitch when using dry pack. The Kerdi is bonded directly to the dry pack and the tile directly to the Kerdi.

No need to backerboard the walls when using Kerdi, sheetrock is fine. ;)

John Bridge
05-27-2006, 02:15 PM

I'm going to argue with David, or at least question what he is saying, and I don't do that often. :) I don't understand what he means about skipping the deck mud altogether and yet create a slope for the liner. Unless the concrete itself is sloped, I have no idea what he's talking about. So we need to get that straightened out. ;)

I think the process might be a bit more complicated that you suppose. Go to the Shcluter web site and view the Kerdi shower video.

05-27-2006, 05:40 PM
Several times recently, in my last twenty posts, I have written about how I built a sloped concrete floor on top of an existing concrete slab, and how I did it without using Deck Mud.

That saved me from having a raised floor.

Since Deck Mud's minimum thickness is somewhere far greater than 1/4", I used another product. I called a cement manufacturer and they recommended a product to me. I asked them if they had any alternatives that cost more. They named another product, that was polymerized. Both were good suggestions. These are cement products that don't need more than "feather" thickness to start with, and can build up thickness to about 1/2". And you can do a second coat if you want to, to get more thickness than that.

The New Zealand member signed in here, Rob with username Oogabooga, just posted in another thread replying to me that he has started chiseling down into concrete slabs in order to then build a clean slope from a lower point so that the shower doesn't need a big bump for a sill, or no sill at all.

He also does not use Deck Mud on concrete. He also skips, eliminates, foregoes using Deck Mud.

I know people in Montreal who have worked with concrete all their lives, and so have their parents and grandparents. They are born in concrete families. To them, everything I have just said above is SO obvious that it doesn't need saying. And they also scrape out shower slopes in existing concrete slabs, and patch it up to make a perfect slope, when they work as renovators and remodelers.

The products to use in my town are known as Resurfacing Mix, Grout Mix and Patching Mix. Other names will apply elsewhere, I am sure.

Deck Mud is also called Sand Coat or Sand Mix.

On wooden joist structures the above methods do not work, as far as I know.

Last December I posted in my big long running thread ("Shared shower...) about needing to find another way to make a slope on top of concrete without using all that sand that would require me to start a lot higher in the center where the drain is and then just keep on getting higher and higher as I moved away from that raised drain.

No-one answered.

Prior to that, I PM'd a moderator who had been involved in creating the Liberry thread on How to build shower floors with slope,,, and he responded agreeing with me that there must be a way but he had never seen it yet or read it yet.

Hope this helps everyone get the context. Here we have a big gap which can be filled, in 2006. How to slope your shower floor on a concrete slab while keeping floor high to a minimum. I believe this is good news.

05-27-2006, 06:02 PM
In your first post, Cain, you said you had already a shower that worked. So, I guess, it already has a slope.

Perhaps you don't need to increase the slope at all, and it will be enough slope for the re-built shower.

If your concrete is all roughed up after you demolish the previous one, you can patch the surface of the concrete easily. The right product will not be any of the three normally referred to here (SLC, thinset, and Deck Mud). It'll be something like a Patching Mix or a Resurfacing....

Then, after your slope is up to your standards, you have to put a liner. That was the whole purpose of your initial query.

Kerdi is a liner. Kerdi will work. Very well. The guy who you can reach on the phone at Tile-Experts, Dave Taylor (often referred to here), is one more person who can also tell you about building or rebuilding sloped floors on concrete without adding any extra layer known as Deck Mud.

So, to answer your post above at noon today, yes you can use Kerdi. And it is always good to remind the reader in each post that you already have a slope. Otherwise you'll get the kind of response that the next person posting gave you.

Key words: "I'm on concrete" and "I have a slope already"