Help, my husband has installed an acrylic shower base. He had to move the drain a couple of inches to meet the drain in the Shower base. We are having a discussion on the hole that is left in the cement floor. He thinks he does not have to fill in it, since the base fits directly on top of it. Is this true. I am concerned about gases coming into the house. Secondly, I have been reading about other installations and found out that the base should be installed with some sort of mud or thinset mortar. Is this true. What happens if it is not.
Please, help solve our marital dispute.

The hole should be filled with crment and if the manufacture suggests bedding the base so it doesn't flex or give when you step into it you may "puddle"crment or thin set ender the base as you set it. Make sure you bed around under the drain. If you don't have instructions to bed your base click on back and we'll walk you through the process. Good luck, Tom

Thank you, The instructions didn't say anything about "bedding" the base, but my husband was going to put an adhesive of some sort under it. Please explain "bedding".

You have,what we call, a manufactured shower base and enclosure as against a custom tile one. If the shower floor "gives" a bit when you step on it the drain seal might be ruptured allowing water to run down outside the drain onto the floor. You puddle mortar or cement under the base for support especially around the drain. If you can get to the underside of the base I would suggest bedding it so you don't end up with a ruptured drain seal.. Good luck, Tom