This shower was very poorly installed, the floor and the curb are uneven and don't slope toward the drain properly so water pools causing this failure after only two years.
To get the shower back in service as quickly as possible and with limited budget available, we removed and reset the loose tiles, re-grouted the floor and the curb, repaired some caulking, and gave everything a good deep clean.
The underlying problem will be addressed at a future date, but this shower will be usable for a while at least until it can be replaced.
