How I Discovered the Problem
I was replacing the bathroom faucet when I noticed the soft spot. Pushed my thumb against the wall about six inches above the tile edge. It gave way more than drywall should. That sick feeling hit my stomach.
Grabbed a utility knife and cut a small inspection hole in the painted section above the tile. The paper backing was gone. Just crumbly gypsum behind it. I could smell the mustiness before I even got my flashlight in there.
The Extent of the Damage
I made the hole bigger. Then bigger again. The rot extended about 18 inches above the tile line and ran nearly the full width of the shower wall. Black mold spots dotted the back side. The wooden studs were stained but still solid, thank god. My neighbor Frank had dealt with rotted studs in his bathroom and that turned into a $4,000 contractor job.
Why This Happens
Water finds a way. In my case, the caulk joint between the tile and the tub had cracked years ago. Every shower sent a little moisture down that crack. It wicked up behind the tile through the grout lines and soaked into the regular drywall that some genius had installed in a wet area.
The previous owners had tiled over standard drywall instead of cement board. That's fine for a kitchen backsplash. Not fine for a shower surround. Regular drywall absorbs moisture. Cement board doesn't.
The Repair Process
No way around it. The tile had to come off. You can't repair drywall behind tile without removing the tile first, and you can't reuse tile that's been pried off. So I was also looking at new tile. The $200 repair became an $800 project real fast.
Removing the Tile
I started at the top row and worked down with a pry bar and hammer. The tiles popped off easily because the drywall behind them had no strength left. Some came off with chunks of gypsum still stuck to the back. Took about two hours to clear the shower walls. Wore safety glasses and a respirator. Flying tile shards are no joke.
Cutting Out the Damaged Drywall
Used my oscillating tool to cut clean lines around the damaged section. Extended my cuts to the nearest studs on each side so I'd have something to nail the new material to. Pulled out the rotted drywall in soggy chunks. Let the studs dry for two days with a fan blowing on them.
Installing Cement Board
No more regular drywall in wet areas. I used 1/2 inch cement board for the replacement. Scored it with a utility knife, snapped it on the line, and cut the back paper. Screwed it into the studs with cement board screws every 8 inches. Taped the seams with alkali-resistant mesh tape and thinset.
What I Spent
Here's the damage to my wallet:
- Cement board (two sheets): $28
- Cement board screws: $9
- Mesh tape and thinset: $22
- New subway tile: $180
- Grout and thinset for tile: $45
- Caulk: $8
- New shower valve (decided to upgrade while I was at it): $85
Total: About $380, plus two weekends of work. Still cheaper than Frank's contractor bill, and now I know the job's done right.
Lessons Learned
Check your caulk lines twice a year. Takes five minutes. When grout or caulk cracks, water gets in. By the time you see signs on the outside, the damage behind is already significant.
Also, if you're tiling a shower area, use cement board or Kerdi membrane. Regular drywall does not belong in wet environments, no matter what the previous owner decided. I found out later this was common in houses built in the early 2000s when builders were cutting corners during the housing boom.
Maria still brings up the grout thing. I don't argue anymore.