FAQ: Integrating Solar Panels on Overclad, Refurbished or Repaired Roofs

Solar viability is primarily driven by energy consumption, rather than the roof condition or size.

As a general guide, solar becomes commercially attractive where a building operator/tenant is spending £60,000 or more per year on electricity. Higher on‑site consumption allows more, or all, of the generated power to be used directly as grid export is not preferable. This also ensures the fastest ROI or if a power purchase agreement is a possibility, the best possible KWh rates.

In addition, a site will typically need a minimum of 1,000 sqm of usable, unshaded roof space with appropriate structural capacity.

For these reasons, roof condition assessments along with potential solar suitability, should always be combined with our energy analysis, which means the provision of the half hourly data for (if possible) two years.

Yes. Overclad roofs, whether metal, asbestos, fibre‑cement or composite, can accommodate solar if the structure allows.

Under UK Building Regulations, adding solar panels is classed as “Installation of a Controlled Service or Fitting” and often a “Material Alteration” due to added load. Structural suitability must therefore be confirmed.
Solar panels typically add around 20 kg/m², which can represent up to a 15% increase in roof loading, triggering Part A compliance requirements.
MCRMA guidance stresses that ageing roofs should be surveyed by specialists to assess fragility, load capacity, wind loads and compatibility of mounting systems before any PV retrofit is approved. [labc.co.uk] [mcrma.co.uk]

Usually, yes. The Planning Portal confirms that the existing roof’s ability to carry the solar load must be checked, and strengthening work may be required.
Compliance with structural safety, electrical safety and ventilation requirements is also mandated under Building Regulations.
We can handle this for you as we’re an accredited member of the government-approved roofing competency scheme NFRC CPS [https://nfrccps.com/]

Usually, yes. The Planning Portal confirms that the existing roof’s ability to carry the solar load must be checked, and strengthening work may be required.
Compliance with structural safety, electrical safety and ventilation requirements is also mandated under Building Regulations.
We can handle this for you as we’re an accredited member of the government-approved roofing competency scheme NFRC CPS [https://nfrccps.com/]

Yes. Overcladding presents an ideal opportunity to add solar because:

• The building is already undergoing structural improvement.
• Insulation upgrades can be incorporated beneath the new external layer.
• The overclad layer can be designed to support and weatherproof solar components from the outset, improving long‑term performance and aesthetics.
• Lower access costs though scaffold/craneage already being on site for the overclad works, will reduce the cost of supplementary hire for PV installation.

With appropriate system design, yes, it can be possible. Overclad solar systems allow PV to be applied to otherwise fragile roofs, including asbestos sheet roofs, by creating a new load bearing structure above the original surface. This new structure can isolate the risk as well as provide a new surface to support a PV system, thus transforming the roof to both a non-fragile structure and one which generates energy.

When installed correctly using certified mounting systems, retrofitted PV should not compromise waterproofing. When it comes to older buildings, Historic England guidance emphasises that mounting details must avoid disrupting tiles, slates, or roof membranes to prevent moisture ingress. In addition, roof manufacturers (under our instruction) will perform a project specific wind load calculation for the project to provide us with the correct and specific fixing pattern for your project, location and system. [historicen…and.org.uk]

Yes. Modern commercial systems often use B Roof (t4) fire‑rated (the highest possible fire safety classification for roofing systems under the European standard BS EN 13501-5) to accommodate solar panels to meet stringent safety and insurance requirements.

For systems including battery storage, Zurich Insurance guidance highlights the need for fire‑rated compartments and safe management of lithium‑ion battery risks (e.g., thermal runaway). [https://www.zurich.co.uk/]

Yes, if the roof is structurally sound. If only small repairs are needed and the roof retains adequate loading capacity, solar can be added as long as structural integrity and waterproofing are validated and of course if we, as professionals, feel that the roof will last another 25 years or the anticipated life of the panel. Not all installations need to be to new roofs for that reason, but equally, a new solar PV system should not be installed on a failing roof.

Very little. Overcladding allows installation without removing the original roof, drastically reducing disruption to operations. Solar systems are designed to be installed efficiently while the building remains in use. Bear in mind scaffold will most likely be required.