I recently installed a tub/shower wall surround kit. I don't remember the exact model, but it was 5 piece kit from the big orange home improvement store. Three wall sections and two corner sections. The corner sections overlap the wall sections. During installation I made sure to follow the instructions and used the shower wall adhesive kit it recommended.

I used the recommended amount of adhesive and used a trowel to spread the adhesive and then used the notched side of the trowel. I made sure to apply lots of pressure on the wall panels so it would stick properly. I waited a day and then caulked all of the seems.

It has been 3 weeks since the shower surround was installed and last night the shower was used for the first time. While the shower was running I noticed the shower walls bubbling out in some areas. This only happened on the front and back wall panels. The side wall and corners peices do not show any air pockets/bubbles. It's almost like the adhesive stopped working when the walls heated up while the shower was running. It seems the heat from the shower caused the bubbling and since the bathroom has cooled down the bubbles/air pockets are no longer visible.

Any ideas on why the shower walls would do this? Any ideas on how to fix this?

 

What is the base material that you glued the shower kit to?

 

Sheetrock. The moisture resistant kind.