The Shower That Looks Fine: How Water Gets Behind Tile and What It Does to the Wall Underneath

The most expensive bathroom repairs we do start with a shower that looked perfectly good. The tile was intact, the grout was clean, and the wall behind it had been wet for two years. Here are the signs, the usual causes, and why this one is almost never covered by insurance.

How it happens

Tile and grout are not waterproof. They are water-resistant, and they depend on a waterproof layer behind them. In houses and condos around Boston built or remodeled before the mid-2000s, that layer is often a sheet of drywall or greenboard with nothing over it. Water works through hairline grout cracks and the joint where the tub meets the tile, soaks into the board, and stays there. Because tile does not show water stains, nothing looks wrong until the board has turned to mush and the tile starts to move.

The signs

• Tiles that sound hollow when you tap them, or that flex when you press on them
• Grout that keeps cracking in the same place no matter how often it is redone
• A soft spot or bubbling paint on the other side of the shower wall, often in a closet or hallway
• A musty smell in the bathroom that cleaning does not fix
• Caulk at the tub line that is black underneath when you pull it up

What we find when it comes apart

Wet, crumbling backer board. Framing that is stained and often soft at the bottom plate. On a second-floor bathroom, a subfloor that is dark around the tub. Mold on the back side of the board more often than not, because it has been dark and wet for a long time. On a recent job in Quincy the owner had regrouted twice; the stud behind the valve had been wet long enough to rot through.

Why insurance usually says no

Homeowner policies cover sudden water, like a burst supply line. Slow seepage over months or years is excluded on almost every Massachusetts policy. A failed shower pan or grout is treated as maintenance. The exception is when a pipe inside the wall actually breaks, which is why we open the wall carefully and photograph the source before anything is thrown away.

The repair

Tile and board come off down to the framing, wet framing is dried or replaced, mold is treated, and the wall is rebuilt with cement board and a real waterproofing membrane before new tile goes on. It is a bathroom remodel, and the good news is that done this way it does not happen again.