Shower Remodel with Prefab shower pan

[Kim]

Hi there,
My name is Kim and I have been reading this forum and have found some great info. Thanks!! However, I still have a couple of questions about my shower remodel job. We are using a prefab Marbelite shower pan to make the base as waterproof and as easy as possible. I hate water leaks!!

I have a 36x60 prefab marbelite shower pan with a 12" deep seat built at one end. The walls and seat are framed and the shower pan is installed on a 1/2" plywood subfloor that is glued to the OSB house subfloor.

My question is what is the correct order of the base materials on the walls to install porcelain tile around a prefab marbelite shower pan??

This is the order of materials that we understand...
1. Wall Stud
2. 4 mill plastic
3. Cement board (We have 1/2" durock but is there something better?) with fiberglass tape joints sealed with latex modified thinset.
4. Paint on waterproof sealer (any suggestions?)
4. Porcelain tile with latex modified thinset adhesive (is premixed adhesive ok or is the powder better to use?)

The marbelite pan installation instructions show the backerboard butting up to the top of the lip of the pan. Then the wall material (in this case porcelain tile) extending past the backerboard (where it meets the pan lip) and covering the rise of the lip (about 1.5"). The small gap between the wall material and the shower pan is sealed with caulk. Does this sound reasonable?

We are using 20"x20" porcelain tile on the walls, do I need any special expansion joints? If so, how would I do it?

We started out using a 40mill red membrane beneath the shower pan but it didn't fit right and it couldn't be installed properly under the pan. Marbelite also says it is not necessary with the prefab pan. What do you think?? It would be a HUGE hassle to go back now and put it in. Not sure my hubby would even do it...

I'm sorry about all the questions but we are so close to the point of no return I want to make sure we are doing it right!

Thanks again!!
Kim

[Jason_Butler]

Hi Kim,

If you are using a prefabbed pan like the photo below, there is no need to put any type of membrane between the base and the floor.

As for you sequence of materials, sounds like you have it covered. If you use the poly / felt paper between the stud and the CBU, there is no need for any liquid waterpoofer. I say stick with the felt / poly

Durock is fine.. I prefer Hardibacker since it cuts easier/cleaner

No problem with expansion joints on the 20's. You will need a big saw though for such a large tile.

DO NOT USE ANYTHING PREMIXED !!!!! NEVER in a wet area. I don't care what the tub says on the back. Stick with a good latex modified thinset for the entire job - even the joint taping. I like Custom's Versabond. Home Depot carries it. Mix it only with water.

Jason

[John Bridge]

Hi Kim, Welcome.

I would have put Jason's admonishment about "pre-mixed thin set" at the top of the list. They ought to be jailed for calling it that. It's nothing but glue and it re-emulsifies when it gets wet.

You will have to waterproof the seat area -- the entire seat and all the adjacent wall areas. Usually, the waterproofing it taken up the walls at least six to eight inches from the seat top and front.

It's very important that you set your shower base absolutely level all the way around. Do they say anything about using cement mortar under the unit to support it?

[Kim]

Wow, 2 replies when I got to the computer this am - AND on a holiday weekend!! I am impressed.

Your replies were just what we wanted/needed to hear.

Jason, when you say poly do you mean plastic?

Yes, the shower pan is the kind you showed Jason. It is level left to right and front to back. The instructions say that if it is NOT level, then level it with cement and shims is needed. Otherwise no cement is needed. I picked it because I thought it would be more leak resistant and easier to install. Do many people use them?

The premix stuff that was bought will go right back to the store ) I knew we were in for several trips to HD today. I had read not to use the premix before on other posts but needed to hear it again.

To waterproof the seat, can we use the 40mil red membrane we tried on the floor (and we scrapped) and use it for waterproofing the seat (underneath the CBU?) or is liquid waterproofing only over the top of the cbu OK?

I will take a picture later today after I clean out the memory on my camera.

Kim

[John Bridge]

Kim,

Don't use the red 40 mil vinyl (Pasco) over the seat. It's only for ceramic tile shower floors. For the seat use Red Guard from Custom Building Products. It is sold at Home Depot in one-gallon containers. You should use the fiberglass cloth reinforcing that comes with the Red Guard in the junctures of the seat and the walls. The waterproofing needs to go up the walls about 6 inches or so. Red Guard goes ON TOP of the cement backer board. Thin set sticks to it, so the tile goes right over it.

So on the seat from the bottom up you will have your wood, then the cement backer board (bedded in thin set mortar and screwed or nailed to the wood). Then the Red Guard spread over the whole seat and onto the walls all the way down to your shower base onto the lip. Then the tile over that installed with thin set.