can a double drywall wall be replaced with cement board or backer board?
One layer can be replaced with a cement board and still be fire rated in most all areas. Using just one layer you can still be flush and use an SBN (surface bull nose) to trim it out. Any questions you can e mail me through my avatar and check my qualifications there. GL
Usually doubled up drywall is a firewall. I'd check with your local code enforcement people and see what they say.
