Dead load is the gravitational force exerted by the self-weight of a roof structure and everything permanently attached to it. In solar PV pre-construction assessments, the PV array dead load is added to the existing roof dead load to determine whether total combined loading remains within the structure's design capacity.
UK structural engineers assess dead loads under Eurocode 1 (EN 1991-1-1) and the UK National Annex. For commercial roofs, the existing dead load is calculated from construction drawings or measured on-site, then combined with the proposed PV array weight per square metre to verify structural utilisation across all relevant Eurocode load combinations.