Flat roofs present different structural and installation considerations for solar PV compared to pitched roofs. Arrays are typically installed on tilted frames to achieve optimal orientation, which introduces additional wind load complexity due to pressure differentials across the panel faces. Structural engineers assess the combined dead load of the mounting frame, panels, and any ballast against the flat roof structure.
Waterproofing integrity is a primary concern for flat roof solar installations. Any racking penetrations through the membrane require specialist sealing, or a non-penetrating ballasted system is used. Ballasted systems require confirmation that the roof structure can carry the additional ballast weight, which at 20 to 30 kg/m² for concrete blocks represents a substantial added dead load on older structures.