A Revit system family, created by footprint, extrusion, or face, that forms a building's uppermost weatherproofing layer and can carry a pitch. The most common method - Roof by Footprint - sketches a boundary and applies a slope to selected edges, while Roof by Extrusion sweeps a profile along a path for more complex forms. Like walls and floors, a roof's layers (structure, insulation, waterproofing) live in its type, and it can host dormers, skylights, and other roof-based families.