it is very common now a days to see most contractors using cement board on the walls in tub/shower areas. It has largely replaced moisture resistant sheetrock which has been used for years epecially before cement board was available. Moisture resistant sheetrock is still used everyday and is an excellent product for all the walls and ceiling of your bathroom, just not in the tub/shower area. When sheetrock is used in the shower area it will most likely fail within 3-8 years due to the fact that it is moisture resistant and not water proof.
Today moisture resistant sheetrock has been replaced in the shower area with cement board. Cement board is a water proof product and will not deteriorate when in direct contact with water. Cement board is made using actual cement with a fiberglass mesh exterior.
Cement board uses:
- Bathroom walls and floors.
- Kitchen countertops
- Soffits in bathrooms
- Exterior uses before stucco or cultured stone is installed.
- Kitchen floors.
The conclusion is that cement board is the only product you should be using when there is any chance of contact with water. Many times its what you don't see behind the walls that has the biggest impact for longevity of your project.