I have some tongue-and-groove boards that my sister wants to use for her kitchen/living room ceiling. The boards are 3" wide, 3/4" thick. Her current ceiling is sheetrock with that 'popcorn' paint on it. It has cracks in it. She's tried to repair them but they keep coming back. Does anyone know if you can simply install these boards over the sheetrock or does the sheetrock need to come down first?? Thanks.