What Happens When Water Gets Under a Tile Bathroom Floor?

Water usually sneaks in through damaged grout or a cracked tile. Grout is porous and can absorb moisture over time, especially if it was never sealed. A loose tile edge or a gap around the tub or toilet gives water a direct path to the layer below.

Steam from hot showers and splashes from the sink can also work their way into tiny openings. Once water is under the tile, it does not evaporate easily because the tile traps it. That trapped moisture starts to affect the materials underneath.

• Cracked or missing grout
• Loose or hollow-sounding tiles
• Gaps around the tub or toilet base
• Unsealed grout lines
• Steam and splashes over time

The subfloor under your tile is often plywood or cement board. If it is plywood, water can cause it to swell, warp, or rot. That weakens the base that the tile sits on, so the whole floor can become unstable.

Moisture can also spread to the wall framing or the floor joists below. If you have a second-floor bathroom, water can soak into the ceiling of the room below. You might see a stain or feel a soft spot in the floor before you notice the tile problem.

Local water damage pros will start by finding the source of the water and stopping it. They may need to remove the affected tile and grout to inspect the subfloor. If the subfloor is wet, they use drying equipment to pull the moisture out and prevent further damage.

The repair work usually involves replacing any rotted or swollen subfloor, then installing new tile and grout. The pros can also check for mold and treat it if needed. The exact steps depend on how far the water spread and what the subfloor is made of.