shower floor repair

[pinkertonpv]

The Master bath shower in a 20 yr old house I recently purchased had a major water leak. The shower is 4 ft by 8 ft and is lined with cultured onyx.

The floor had several cracks that had been caulked to stop the leak. After checking the floor from the crawl space and seeing the rotted wood, I removed the floor with hammer and chisel/crowbar. Underneath the floor was about 2 1/2 inch thick circles of what appeared to be Quickrete.

After removing this I was down to the rotted sub-floor. There was no pan liner, membrane or any thing else between the concrete and sub-floor. I removed and replaced all the rotted wood.

Replacing the shower floor with a one piece onyx pan is way too expensive so I will build a prepan, membrane, pan and then tile the floor.

I will have to cut the bottom 6-12 inches of onyx all the way around the shower on the walls to be able to install the membrane on the wall studs. I hope this will stop any leaks if I do it properly. I will leave the remaining onyx wall sheets in place. Then I will install the pan, cement board over the membrane on the wall where I removed the onyx, waterproof it, and install the tile on the cement bd. A problem is the joint between the tile and onyx.

My question is about the joint where the tile and onyx will meet at the 12 inch line above the floor. I want to insure this is waterproof. My plan is to install ceramic tile trim at this joint around the entire shower. I hope to make it decorative like the contrast between different color tiles in a bathroom border.

Also, should I install the tile floor before I put cement bd on the walls?

Any comments are welcome.

[pushkins]

This is probably around an 8 out of 10 in the DIY difficulty scale, however if you have good DIY skills, take your time and follow a few simple but very important rules it is doable.

The rubber membrane NEVER goes directly on the sub floor, you need to build the first layer of sloped mortar bed first then install a liner.
What you should do is the following:

On the repaired sub floor lay a layer of roofing felt cut to fit around the new drain, add 2x4 blocks on their side between every stud cavity screwed in place flush with the interior of the studs, then you will mix a batch of "bedding mortar" (you can buy it ready to mix at any big box store in the tile department) it should be so that it comes level with the lower flange on the drain that is screwed to the sub floor, with a slope of around 1/4" / foot so it will slope upwards to the wall surround, chalk lining the walls all the way around is a good idea to make sure you get consistent levels, this slope is the basis of correct drainage of the shower stall so take your time. Mix the mortar so it's dry, you do not want wet mortar when you install it your going to pack it down hard with a float.
The drain should be an adjustable type with the center drain section threaded so it can be adjusted up or down, allow this to dry overnight. Next you will install the rubber membrane add a bead of silicone on the drain flange, install the liner cutting little slits to allow the bolts to poke through, bed the liner into the silicone, install the liner cap section of the drain and tighten the bolts. Smooth out the liner into the corners, fold over the corners to allow the liner to be nice and snug in the corners. You want the liner to come up the wall at least 4", 6" is much better, If you need to join the liner make sure you use liner contact adhesive.
You'll notice that now you have a sloped rubber surface from the wall all the way to the drain, at this stage add your backer board to the walls screwing it over the top of the liner DO NOT use screws or nails in the lower 4" of the liner, the backer board should stop about 1/2" up off the liner.
Now your going to put some small pebbles all around the drain, you won't need many usually just a hand full and only 1/2" thick. Now your going to add the second layer of mortar bedding, lower the top of the drain to allow at least 1" of new mortar at the drain, from this height again mark the walls (it will be on the backer board) all the way around the stall so that there is at least 1/4"/ foot fall towards the drain. Mix and install the mortar starting at the drain making sure that the pebbles remain around the drain (they are for drainage allowing moisture to weep from the mortar bed and into the drain weep holes) the mortar should cover the pebbles and be lower than the drain top by the thickness of any finish tile your installing. Again your going to use a dry mix and pack it down with a float, it is very important that the mortar bed is compacted down. Allow it to dry.
Now you should see a completed mud bedding with the wall backer board embedded in the floor, the top of the drain should stick out of the floor bed by the thickness of any finish tile your going to use.

The common thought is that the mortar is the water proof, it is not, the mortar will get wet (and be wet for the rest of the showers life) it's the rubber liner installed over the first layer of sloped bedding that keeps everything dry, the moisture goes through the top bedding layer hits the liner and drains towards the weep holes in the drain.

Always tile the floor first then the wall, that way the water runs off the wall and onto a tile not a grout joint.
Ideally you want the wall joint to have a tile over the joint (not stopping and starting at the joint) this helps with cracks and with moisture mitigation. So it would be advisable to try to remove part of the tile leaving a wall section intack so when you re tile the tiles will overlap the new joint.