Commercial solar engineering screening flags

Commercial rooftop solar projects often look viable on headline yield and payback — until a structural engineer, DNO, or planning officer raises an issue that changes the economics or timeline. Screening those risks at feasibility stage, before you commission surveys and design, saves money and gives boards an honest picture.

Stage1Energy does not certify structures or submit grid applications. The dossier flags where professional verification is likely needed and names the next step. That is feasibility, not design — but it prevents surprises.

Panels on a flat or pitched commercial roof are subject to wind uplift as well as gravity load. BS EN 1991-1-4 provides the basis for calculating pressure on exposed roof zones. The feasibility dossier estimates wind speed for the site, calculates uplift per panel, and indicates whether a ballasted or penetrative mounting approach is likely.

If uplift exceeds typical ballast capacity or the roof covering cannot accept penetrations, the flag names structural follow-up. Deep dive: wind loading on commercial roofs.

Adding PV increases dead load on the roof structure. A desk-based screening compares array mass spread over the panel footprint against typical capacity assumptions for the roof type — not a substitute for a chartered structural engineer's calculation, but enough to catch obviously overloaded roofs early.

When the screening ratio is marginal, the dossier recommends formal structural assessment before procurement. Read: structural screening for commercial roof solar and feasibility vs structural survey.

Exporting solar to the grid requires a connection agreement from the local distribution network operator (DNO). Installations under 3.68 kW per phase may qualify for G98 notification; larger systems require G99 application with potential queue delays and reinforcement costs.

The feasibility dossier identifies the likely G98/G99 route based on proposed system size and flags when export capacity or queue risk could affect project economics. Guide: G98 vs G99 explained and DNO applications for commercial solar.

Many UK commercial rooftop installations fall under permitted development rights (Class J), but exceptions apply — conservation areas, listed buildings, Article 4 directions, and height limits can require full planning permission.

The dossier runs a permitted development screening check and states the likely planning route. If full planning is probable, the flag notes timeline and cost implications. Read: permitted development for commercial solar.

Each flag is stated plainly in the engineering section of the 29-page dossier — not buried in small print. A flagged item includes what was checked, what assumption was used, and what professional verification is recommended next.

See real examples in the example report (engineering flags section) and the full engineering flags guide. Our approach: methodology page.