· by Michael Blair, Nashville's Drywall Repair
Different boards suit different exposures, and the common error is treating moisture-resistant drywall as a waterproof product. It is not, and in a shower it fails.
The options
Standard board for ordinary rooms. Moisture-resistant board, often green, for bathrooms outside the wet area. Cement board or a foam backer inside showers and tub surrounds.
Paperless glass-mat board resists mold better than paper-faced moisture-resistant board and is worth considering in Middle Tennessee bathrooms and basements.
Green board is not waterproof
It resists moisture in the air, not water running down it. Behind tile in a shower it fails, which is why cement board or a foam backer with a proper waterproof membrane is the correct assembly.
This is one of the most common causes of failed showers in older bathrooms.
- Standard board: ordinary rooms
- Moisture-resistant: bathroom walls outside the wet area
- Cement board or foam backer: inside showers and surrounds
- Paperless glass-mat: better mold resistance in humid areas
- Waterproof membrane over the backer, always
Basements
A finished Middle Tennessee basement should assume some moisture. Paperless board, a gap at the floor, and no organic material against the concrete all help.
Address exterior drainage before finishing a basement, because a finished wall makes any future water problem far more expensive.
Ceilings
Ceilings want either five-eighths board or half-inch board rated for ceilings on wider joist spacing, since half-inch standard board sags over time — particularly in humidity.
Sagging ceilings in older Nashville houses are frequently this rather than a structural issue.