When roof refurbishment and solar PV sit within separate budgets or workstreams, the solar project can move ahead on the assumption that an existing roof is suitable. Confirming structural capacity is essential, but it does not answer every question. A roof may have sufficient capacity to carry an array, but its waterproofing, insulation, fixings, or detailing may not remain serviceable for the expected life of the panels.
If the roof then requires refurbishment, the panels may need to be removed, stored, and reinstalled. The estate faces additional cost, further disruption, and a period without generation. These consequences do not make solar unviable. They show why roof condition and solar potential need to be assessed together, before either scheme is specified.
Start with evidence, not a predetermined scope
A detailed roof condition survey should establish the roof construction, identify defects, and, where appropriate, map moisture distribution and the areas that can reasonably be retained. The findings can then inform the solar design, refurbishment scope, and project sequence. This gives estates teams one evidence base for the business case rather than separate reports that answer different questions.
The value of evidence-led planning is particularly clear on hospital roofs, where plant and service penetrations can constrain refurbishment. As previously reported in HEJ, a detailed survey and moisture scan at Cavell Hospital allowed targeted works to proceed while the hospital remained fully operational, reducing projected plant-related costs from approximately £1m to under £100,000.
Match the life of the roof to the life of the array
The same principle applies directly to solar. At Carr Junior School in York, a roof condition survey and solar yield analysis were commissioned during the early stages of planning. The survey identified cut-edge corrosion, corroded seal washers, and areas where the protective coating on the steel roof panels had failed. Garland UK advised that the roof would likely fail before the end of the proposed solar system’s service life.
The roof was therefore overclad and upgraded before the 28.7 kWp solar array was installed. The completed system is expected to generate 26,287 kWh a year. Although this is an education project, the technical lesson transfers to healthcare buildings; confirming that a roof can bear solar panels is not the same as confirming that it can protect the building for the life of the solar investment.
The same coordinated approach was used at Hambridge Industrial Estate, where an ageing, leaking asbestos cement roof was overclad before a 149.52 kWp solar system was installed. The array is forecast to generate 145,500 kWh a year, while the roof and solar system sit under a single 20 year guarantee.
Define responsibility at the interfaces
Where roofing and solar are designed and delivered as one coordinated programme, the interfaces between the waterproofing, mounting system and penetrations can be addressed within the specification. Depending on the contractual and guarantee arrangements, this can also provide one route for resolving defects instead of leaving the estate to establish whether responsibility sits with the roofing contractor or solar installer.
For financial appraisal, BS ISO 15686-5:2017 provides requirements and guidance for comparing life-cycle costs over an agreed analysis period. It covers relevant costs and cash flows from acquisition through operation to disposal, within an agreed scope. For a roof and solar project, this means comparing combined and separate delivery, including the potential future costs of removing, storing and reinstalling panels.
The practical starting point is simple. If solar PV appears on the estate plan, establish the condition and remaining service life of the proposed host roof before finalising the business case. Where refurbishment may also be required, commission the roof condition survey and solar yield analysis together. Let the evidence determine the scope and sequence.
Garland UK undertakes both assessments, giving healthcare estates teams a single technical evidence base for roof and solar investment decisions.