Commercial solar: roof and building due diligence

Confirm control of the roof

A commercial roof can involve a freeholder, tenant, managing agent, lender, insurer and maintenance contractor. Establish who authorises works and whether lease, licence, roof warranty or lender consent restricts access or alterations. Align the project term with the lease and redevelopment plans.

Document covering, age, repairs, warranties, asbestos information and access. An aerial image does not prove structural capacity or waterproofing.

Clarify who can grant access for surveys and maintenance, who carries liability during construction, and whether the roof warranty requires an approved system or specialist detail. If a tenant occupies only part of a larger building, map the electrical and physical boundaries before inviting proposals.

A roof replacement can be a major future cost. Ask bidders to explain how panels would be removed and reinstalled, whether the roof life supports the proposed contract term, and who pays if an unexpected defect is found. These questions belong in the commercial decision record, not only in a later construction meeting.

Survey structure and operations

A competent professional should assess existing loads, additional dead load, wind uplift, fixing strategy and roof condition. Consider fire strategy, emergency access, cables, plant clearances and maintenance. Construction may require shutdowns, barriers or out-of-hours working.

Map loading bays, cranes, skylights, vents and access restrictions. Put these constraints in every tender so bids are comparable.

Review fire risk information, emergency response arrangements and the building’s existing electrical protection with the relevant professionals. Solar equipment can affect isolation and maintenance procedures, so the finished system needs clear labels, drawings and an agreed handover.

Consider weather exposure, drainage, roof traffic and cleaning access. A layout that fits on a plan may be unsuitable if it blocks gutters, creates maintenance hazards or prevents a contractor from reaching plant. Ask for the proposed maintenance method and frequency rather than treating maintenance as an afterthought.

Build the decision pack

Provide interval data, meters, operating hours, planned expansion, lease information and surveys. Ask each bidder to state assumptions, export limits, outages, programme, warranties, insurance and reinstatement. Do not publish a project as a case study until the owner has approved facts, figures and images.

Give bidders the same roof plans and consumption data, then ask them to identify information still missing. Compare their exclusions as carefully as their prices. A proposal that is transparent about uncertainty is easier to govern than one that presents a precise return before surveys are complete.

For a portfolio, consider whether one roof should be trialled before a larger rollout. Set decision gates for survey, landlord approval, DNO response, final design and contract signature. Keep the business case separate from any public marketing story until the customer has approved publication.

Appoint one owner for the technical record and one for the commercial approvals. Confirm how changes are logged, who accepts the final design and where completion documents are stored. This reduces the risk that a project is handed over with important assumptions known only to the original salesperson.

Common questions

Can a tenant install solar?

Potentially, subject to landlord, lease, lender, insurer, planning, structural and grid requirements.

Is a drone survey enough?

It can support early planning but not structural, waterproofing and safety diligence.

What helps a quote?

Plans, covering and warranty details, surveys, repairs, access, asbestos information and lease requirements.

Sources and further reading

• HSE: work at height
• GOV.UK planning permission
• MCS standards