My house was built in 1977. We finished the basement in 2000.

I have a problem with my basement shower. It has tile walls over backer board and a fiberglass base (32"x48"). The walls of the basement were constructed properly so that heaving or settling of the floor woult not affect the walls. In the bathroom though the base and walls of the shower are directly linked. So when the floor heaved the corners of the shower base split. Unfortunately a crack in the basement floor runs directly under the shower. Now I'm trying to figure out how to redo the shower so this doesn't happen again.

The only idea I've come up with is to buy a one or two-piece fiberglass enclosure (probably two-piece as I don't think I can get a one-piece into the basement). When I attach it to the studs, instead of nailing or screwing through the flange, I thought I'd cut vertical slots in the flange. Then use screws and washers to hold it in place. Instead of covering the flange and screws with drywall, I would surround it with wood trim with the backside relieved and leave a gap between the trim and the edge of the shower. This would allow the entire shower to move up and down as the floor moved. However it also means I can only attach the sides of the enclosure to the walls as there probably isn't enough room in the flange to cut vertical slots along the top of the shower. With the floor still likely to move a little, I'm also not sure how to keep the base stable.

Has anyone tackled a similar problem? Is my idea stupid? Look forward to hearing there's a better way. Thanks!