Prep the Subfloor for Shower Pan Installation
Once your subfloor is stiff and solid, you're ready to start going up with the shower pan installation.
First, you cut a piece of 15# roofing felt to cover the bottom of the shower. The felt can be sized to just fit the bottom of the shower. This is called slip sheet and it isolates the bottom layer of the pan from the subfloor.
One reason for the layer is to prevent the subfloor from pulling moisture from the pan masonry before it dries properly.
You'll cut a hole in the felt for the drain assembly to slip through too.
Now to make sure the first masonry layer stays put, you'll put down a layer of expanded metal galvanized lath. The lath gives the bottom shower pan layer something to get a grip on...
Staple or tack the felt and the metal lath in place.
Now an easy way to get the first layer of masonry at the right angle...
Nail furring strips at the right height along the walls where you'll slope the mud. Use those for guides while building the first layer. After you have the floor slope right, just pull out the guide strips and fill in the empty spaces.
What about installing over concrete subfloor?
You can use the same process. Another option is to omit the felt and the wire. Simply apply a coat of thinset mortar to the concrete subfloor right before poring in the deck mud. That's all that's necessary to get the right fit between the subfloor and the shower floor.
Now about that curb...
Click here for the scoop on building the tile shower pan curb.