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.