What does an inspector look for at a shower or tub surround's corners and joints?

Corners and joints are where a wet-area assembly either keeps water out or lets it into the wall, so that is what the inspector examines. Sealant at the tub-to-surround joint and at inside corners is the front line; where it has failed, water passes behind the surround and reaches the substrate. The substrate is the real subject — behind tile there should be a water-resistant board or a membrane, and where ordinary drywall was used it softens, the tile loses its bond and the framing beyond it gets wet. That is why the inspector presses on the surround looking for movement or sponginess and looks for loose or hollow-sounding tile, since those indicate the backing has already gone. Appearance items such as tile pattern, brand matching and perfect squareness tell you nothing about whether the assembly is keeping water out of the wall.

The joints and corners are where water gets behind the surround, and the substrate behind them is what fails when it does. The inspector checks that joints are sealed and that the surround feels sound rather than soft or loose.

Wet-area walls require a water-resistant substrate and sealed joints at changes of plane and at fixture junctions. Failed sealant admits water behind the surround, softening the substrate and wetting concealed framing, which typically shows as loose or hollow tile and movement in the surround.

Press the Corners. Sealant is what you see; the backing is what matters. Soft or hollow means the water already got in.

Check the room below or the adjacent wall for staining. Concealed leakage from a surround often shows up somewhere other than the bathroom itself.

• •Assessing appearance rather than water resistance
• •Checking sealant without probing for a soft substrate
• •Failing to look for evidence of leakage in adjacent spaces