How water gets in
Grout is porous and cement-based. It is not a waterproof layer on its own. In a properly built tile shower, a membrane or backer system behind the tile does the real waterproofing. In many production homes from the 1980s and 1990s, tub surrounds and showers were built with tile over water-resistant drywall or a basic backer, and the grout and caulk joints carry more of the load than they should.
Once grout cracks, especially at inside corners, around the valve trim and where the tub meets the tile, water seeps in during every shower. The back of the backer board and the studs stay damp. Because the far side of that wall is often a closet with clothes pressed against it, there is little air movement to help it dry.
Fiberglass and acrylic surrounds have their own weak points: the caulk at the tub lip, the seams between panels, and the seal around the faucet and showerhead escutcheons.
Clues on both sides of the wall
- Grout that is cracked, missing, or darker in one area that never dries
- Tiles that sound hollow or move when pressed
- Caulk that has pulled away at the tub or shower pan
- A loose valve handle or trim plate
- Peeling paint or soft drywall in the closet behind the shower
- Musty odor on clothes stored on that wall
- Staining on the ceiling below an upstairs shower
Regrouting versus opening the wall
| Regrouting and recaulking may be enough when | Opening the wall is usually needed when |
|---|---|
| Tiles are firmly bonded and do not flex | Tiles are loose or the backer feels soft |
| The adjoining wall shows no staining or softness | Growth or staining appears on the adjoining wall |
| Moisture readings on the far side are normal | Moisture readings stay high days after showering stops |
| The problem is a small crack caught early | There is a musty odor inside the wall cavity |
What a typical repair sequence looks like
Stop using the shower
Use another bathroom until the extent is known, so the cavity can begin to dry.
Open from the less finished side
Where possible, contractors open the closet side first, which is cheaper to rebuild than tile.
Remove and clean under containment
Moldy drywall and insulation are removed, and framing is cleaned and dried to normal moisture levels.
Rebuild the shower properly
If tile has failed, ask that the new shower include a continuous waterproof membrane behind the tile.
Common questions
Will grout sealer stop leaks?
Sealer slows staining and water absorption at the surface, but it will not bridge a crack or replace a missing waterproof layer behind the tile.
General information for Highlands Ranch, not a quote or professional advice. In an emergency, call 911.