Planning route is the fourth of four engineering flags in every Stage1Energy feasibility dossier. For UK commercial rooftop PV, the default assumption is permitted development — but “default” is not “guaranteed.” Screening the planning route at feasibility stage is how you avoid discovering an Article 4 direction or a lease restriction after the financial case is approved.
What permitted development means for commercial solar
Permitted development (PD) allows certain building works and changes of use without a full planning application. For solar PV on non-domestic buildings in England, Class J of Schedule 2, Part 14 of the GPDO 2015 is the relevant provision.
In broad terms, Class J permits the installation of solar PV on the roof of a non-domestic building subject to conditions including:
- Panels must not project more than 200 mm above the plane of the roof surface (when measured perpendicular to the surface).
- Panels must not be installed on a wall facing a highway in certain circumstances.
- The building must not be within a scheduled monument curtilage.
- Additional restrictions apply in conservation areas, on listed buildings, and where an Article 4 direction has removed PD rights.
Wales, Scotland, and Northern Ireland have their own permitted development schedules. The principles are similar — rooftop solar is generally favoured — but the detail differs. A feasibility screen states which jurisdiction applies and flags where local verification is prudent.
Our methodology describes how we screen the planning route. Class J permitted development detail appears in the example report, which shows a medium planning flag where verification with the local planning authority is the named next step.
When PD applies — and when it does not
Straightforward cases — modern warehouse on an industrial estate, no heritage constraints, panels flush or within 200 mm of a flat roof surface, no Article 4 direction — typically screen as low planning risk under PD. The next step is often “verify planning route with local planning authority” as standard due diligence, not “submit full planning application.”
Cases needing closer attention include:
- Listed buildings and conservation areas — PD rights may be restricted or require prior approval.
- Retail on high streets — wall-facing panels and highway visibility can trigger conditions.
- Article 4 directions — some local authorities have removed PD rights for commercial solar in specific areas.
- Lease and landlord consent — not a planning question, but often the practical blocker. The feasibility flag addresses planning route; lease review remains the landlord’s responsibility.
Screening uses building location, type, and declared constraints. Where data is incomplete, the dossier states its assumptions rather than silently assuming PD applies.
PD screening vs a planning application
A feasibility dossier does not submit planning applications and does not produce design and access statements. It answers a narrower question: does the proposed array appear to fall within permitted development, or is a formal application likely?
That distinction matters for programme and cost. A PD route might need only a Lawful Development Certificate (LDC) for lender or landlord comfort — a lighter process than a full application. A site requiring planning permission adds eight to thirteen weeks (or more) to the programme, plus application fees and consultant costs.
For commercial solar feasibility, the planning flag sits alongside wind, structural, and DNO screening. A roof that passes financial screening but flags elevated planning risk is not disqualified — it is a roof where programme and cost assumptions need adjustment before board approval.
How planning interacts with other engineering flags
Planning conditions can constrain where panels sit on the roof — which affects layout, yield, and wind zone placement. Setback from roof edges may be required by PD conditions or by good mounting practice. A smaller usable area reduces capacity, which may drop an array below G99 thresholds — or simply weaken the business case.
Conversely, a roof with generous PD headroom but elevated structural or grid risk may still be a no-go. The four flags are reported together so the verdict reflects the whole engineering picture, not the most optimistic single check.
Practical steps after screening
Where the planning flag returns low with PD appearing applicable:
- Confirm no Article 4 direction or heritage constraint with the local planning authority or your planning consultant.
- Check the lease for landlord consent requirements — independent of planning.
- Consider an LDC if the lender or asset manager requires formal confirmation.
Where the flag returns medium or elevated:
- Engage a planning consultant or speak to the local planning authority before committing to layout.
- Adjust programme assumptions to allow for a full application if needed.
- Revisit the financial case if planning delay affects IRR or payback.
The free screening does not include engineering flags. The full site assessment adds all four — including planning — with sourced workings reviewed before release.
Limits of planning screening
Be explicit:
- A feasibility dossier is not a planning opinion or certificate of lawfulness.
- It does not search local authority planning portals for prior decisions or Article 4 directions unless declared.
- It does not replace engagement with the local planning authority where the site is sensitive.
It does tell you whether planning is likely to be a formality or a programme risk — which is exactly what estates teams and advisers need before spending on surveys, DNO applications, or installer quotes.
For most UK commercial rooftops, permitted development is the expected route. Screening confirms whether your roof is “most” or an exception.