Eurocode 0 (EN 1990) specifies the load combination expressions used for both ULS and SLS design. For rooftop solar PV assessments, the governing combination typically includes the PV array dead load as a permanent action combined with either wind or snow as the leading variable action, with the other as an accompanying variable action multiplied by its combination factor.
Structural engineers check all relevant load combinations for each structural element assessed. The combination that produces the highest utilisation ratio governs the design. Solar Surveys structural reports set out the critical load combinations applied for each element check, enabling independent verification of the structural assessment methodology.