Decoustics Coffer Ceiling typically used in waffle slab construction to create a ceiling with depth and architectural interest. Sunken panels are attached using mounting J-clips and a minimum space of 2-1/4″ (57 mm) is required behind the panel to ac...See Morecommodate hardware and installation. The back of the panels are typically positioned 2-1/4″ (57 mm) down from the top of the recess in the waffle (coffer). A floating panel effect is achieved via a minimum 1″ (25 mm) wide reveal which is required around each panel to facilitate installation. See Less