The key to a successful installation lies in the use of a chlorinated polyethylene cpe or pvc membrane tough but flexible plastics that form the pan of the enclosure and make the floor waterproof.
Shower pan on a wood floor plywood thickness.
Where a rotten subfloor is left unattended the rot may extend to the floor.
After you have put down a double layer of plywood to provide the base for a custom walk in shower pan you need to cover the subfloor with a layer of tar paper in this case referred to as a vapor.
A mortared shower pan allows you to custom fit a shower enclosure.
A plywood subfloor under a shower also known as underlayment is vulnerable to moisture damage that can rot the wood.
A piece of plywood can be purchased in 1 2 or 3 4 thickness and most cement backer boards will be 1 4 1 2 or 5 8 thick.
I used an unbonded mortar bed so i have a tar.
Water that gets into the mortar bed won t be able to drain out.
Reinforce the shower pan.
No matter what the building inspector says it s not a good idea to install a pan liner and then a single sloped mortar bed over it.