One of the options when installing a tile shower is to use a pre-made fiberglass shower pan (which is exactly what I ripped out of my original shower) but I didn't want that look, or to be constrained by the dimensions that are available. I wanted a 'custom' shower.
|Diagram courtesy of Oatey|
The next step is to pour the "preslope" or the mortar floor below the liner which MUST BE accurately sloped in order to drive water towards the drain. Although water will never come in contact with this layer (since the PVC liner will go over the top of it) it must be 1/4-1/2 inch higher for every foot between the edge of the shower and the drain.
I will make a confession. I really struggled with this step. I used mortar mix to pour the base layer and had trouble getting the slope correct the first time. I spent an entire day ripping out the cement from my first attempt and re-pouring the preslope. This set me back a full day.
What I learned from this fiasco was that I should have used "deck mud" (a 1:5 ratio of cement to sand) instead of the pre-bagged mortar mix (which has a much lower ratio, closer to 1:2.) I will eventually pour the final shower floor using the deck mud mixture, since it was 10 times easier to work mix. The sand slows the set up time as well as make the mixture more malleable. For more info about deck mud, see this great post.
After allowing the preslope to cure overnight, I was able to add the shower pan liner. This PVC membrane is available, by the linear foot, at most big box hardware stores. You want to leave AT LEAST 6 inches up the wall and NEVER EVER EVER put a hole in it. The liner is nailed at the top and outside of the wet areas only. It is not held in place at the bottom of the shower or around the curb by anything other than the cement that is going to be poured over it.
Once the liner is in place you must carefully cut out around the drain. I made sure to leave little notches which lined up with the weep holes and made sure the bolts holding the top of the drain in place were well sealed:
I also tested my preslope when draining the standing water. You want all the moisture to go to the drain. You don't want any standing areas of water where the preslope may dip or not be the proper slope. Happily all the water successfully drained from my pan so I was very happy.