Yes, even though our Box-Beam Systems provide complete coverage of the ceiling surface you must install a layer of drywall for 2 main reasons:
1. Your local fire code will more than likely require a layer of drywall on the ceiling as a fire barrier between floors along with a scratch coat of tape and joint compound.
2. It will provide a clean continuous surface on which to mark center of the ceiling and to snap guide lines to aid in the installation process.