Our contractor says green board is required for his corian shower because it is coved and waterproof. Is he right? The City says cement board is a new requirement because mold can get in. However, they will accept the manufacturers recommendation. We want to follow the building code.
Fibre cement board should be used in showers, bathrooms, and other 'wet areas'
Absolutely, spend $30 more and use cement board. As a builder, I always line the studs with plastic, which overlaps the shower pan, then screw cement board over the plastic overlapping the shower pan (usually PVC product), then use red guard to seal seams and screw holes, then apply thinset mortar for tile, or mastic for corian, then seal all joints with grout sealer. It's your house and your money...stick to your instincts.
If the building code allows the manufacturer's recommendations for installation and the manufacturer recommends mold resistant green board, then green board would be acceptable under the code. Cement board would be required in any installation where there are no specifications from the manufacturer.
