How to Fix a Flexing Shower Base?

In severe cases—especially if the flexing has caused the shower pan itself to crack—the only solution is to remove the base to make the necessary repairs. This can involve better shimming for the support ribs beneath the pan or laying a mortar bed to support the pan over its entire surface.

What do you put under a shower base?

Mortar is recommended to use under all shower pans. Mortar reduces the risk of your pan slipping or cracking from an uneven surface.