Shower Drain/Mortar Bed

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Shower Drain/Mortar Bed

Post by jvelaz1971 » Wed Apr 10, 2019 7:36 am

Hi Shannon,
Hope all is well. I am converting my corner Jacuzzi into a 3x5 shower. I will be tapping into the existing drain and water lines. So this will not be an issue for me. My sub floor will be plywood. To what height should I place my drain? Also, do you have a video that shows the very next step, which is to mix the mortar that goes over the sub-floor and put it down with a slope of ¼ for every foot? I really can use this type of video from beginning to end. Also, do you have a video for installing the liner and the mortar over that? Unless the video for the first step is exactly as the second step. I just don’t know where and how to begin the first step after installing the drain. Any help will be greatly appreciated.

Thank you

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Re: Shower Drain/Mortar Bed

Post by Shannon » Wed Apr 10, 2019 7:42 am

I have never done a mortar bed shower base. I have always either used a fibreglass or acrylic pan or used Schluter shower pan systems. In your case with the drain likely being in a bit of an odd area neither of those would likely work.
I believe Spruce and maybe Dan have experience with what you are using so lets see what they say.
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A. Spruce
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Re: Shower Drain/Mortar Bed

Post by A. Spruce » Wed Apr 10, 2019 9:18 am

I have never personally done a mortar bed installation, I've always left this to my sub-contractors. What I can tell you is this:

1 - Subfloor and framing must be suitable for the load of the mortar and tile to keep it from flexing which results in cracking.
2 - The drain pipe is installed wherever you wish to locate it, usually the center of the pan, but it can go anywhere. There is a separate collar that is installed over the pipe and screwed to the floor, this sets your pan thickness and pipe height. A rubber donut is pushed in to make a seal between the two.
3 - In my day we used a process called "hot mopping", where layers of molten tar and roofing paper are applied to the floor and up the wall 8", and over the curb. This is what creates the waterproof pan.
4 - The mortar bed is installed and sloped accordingly. The way I've seen this done is the mortar is mixed to a wet sand consistency, a flat/level layer is installed and lightly packed. Shims are cut and that extend from the walls to the drain, it is these shims that guide you to your 1/4" per foot slope towards the drain. Once the mortar is installed and packed, the shims are pulled and their cavities filled.
5 - The walls can be done several different ways, tile backer board or with mortar base, the methods for installing these are unique to the method chosen.
6 - The floor is tiled first, then the walls. Make sure you lay out your tiles properly, you do not want scabs along edges, you want your edge tiles to match in dimension.

I would recommend checking out the John Bridge Tile Forum for specifics on all the processes.
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Re: Shower Drain/Mortar Bed

Post by DanM » Sat Apr 13, 2019 5:19 pm

Hopefully it's ok to post links to other youtube channels. For how to videos with regards to tiling Sal Diblasi's has everything. There's multiple videos just on doing the mortar bed stages (videos about different combinations of products, different types of sub-floor, or just different types of techniques). ... MuuV8-C0pQ

A few things you'll need:

-A bit of tar paper and metal lath (enough to put a layer on your sub-floor)
-Staples that can handle contact with cement (I used stainless steel fence staples, like you'd use to attach barbed wire to a farm fence)
-A 3-piece drain (there's a bottom piece that ties into your plumbing, a collar that screws into the base, and a threaded top piece that screws into the collar).

Here's a basic rundown of the steps, but I recommend watching the videos on that channel. There's lots of commentary about each step (and why this or that is important to do).

1-Put 2x8 blocking in between every stud around the shower (this gives solid support for the liner, edges of the mortar beds, etc). Build a shower curb. 3 or 4 2x4's stacked on top of each other works great. 3 will give you a final height of around 6 inches ( 4 1/2" for the wood, 1/2" for cement board, and 1" for a one-piece marble shower curb). If you don't mind stepping over (or visually prefer) a 7 1/2" step add a 4th 2x4.

2- Set the bottom piece of the 3 piece drain so the underside of the top disc is 1 1/4" above your subfloor. Mortar beds need to be at least 1 1/4" thick or they'll be too weak and brittle.

3- Lay down a layer of tar paper on the sub-floor, then lay down the wire lath on top of it. Staple the wire lath to the sub-floor. The tar paper is just there to keep the plywood from drinking all the water out of your mortar (which will be a dry mix), this just helps the mortar cure properly.

4- Mark a line around the perimeter of your shower 2" up from your sub-floor. That'll give you your 1/4" per foot slope towards the drain (which is of course 1 1/4" off the sub-floor).

5- Starting doing your pre-slope mortar bed. I won't go into detail on this, it's far easier to watch one of the videos and see how it's done.

6- Install your liner and bolt the drain collar into the drain base. Screw the upper drain into the collar so it sits [1 1/4" + the thickness of your tiles] above the drain collar.

7-Put a bunch of pea gravel around the drain (the videos will show you how much to do).

8- Prep for the upper mortar bed. The whole thing needs to be 1 1/4" thick so mark a line around the perimeter of the shower 1 1/4" up from the liner. Then do the mortar bed the same way as before, and try to gauge it to also be 1 1/4" thick near the drain.

9- Now do your cement board (or DensShield, or whatever product you want) on the walls, etc. Waterproof it, and you're ready to start tiling.

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Re: Shower Drain/Mortar Bed

Post by jvelaz1971 » Thu Apr 18, 2019 11:43 am

wow, all this information is great. Thank you so much. I feel much better about this project now. I will follow the steps to exactly as outlined.
Thank you all again!

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