Protected Membrane Roof - Paver Ballast Typically requires crushed, graded stone placed over a stone filter sheet, rolled out over the insulation. In the field of the roof, a minimum of 10 lbs./s.f. ballast is required, with 20 lbs./s.f. needed at perimeters and at large penetrations. Listing Back To Top Design Visualizer Previous Next Design Visualizer 3D You need to be logged in to view & download files. Login/Register New to CADdetails? Register to enjoy full access to unlimited 3D models, CAD drawings and specifications. It's free! Downloads Product Info About Education BIM Revit Template Specs Specs Download All Add to Project+ Favorite User Feedback