If your commercial roof is getting old and you are thinking about solar, the order you do things in matters. Fit panels to a roof that will need replacing in a few years and you will pay to take them off and put them back again. This guide explains when re-roofing first makes sense, how a combined roof and solar project works, and what the combined warranty covers.
Why roof condition matters before solar
A commercial solar array is designed to generate for 25 years and more. The roof underneath it needs to last at least as long. If it does not, you face a second project later: scaffolding, removing the array, repairing or replacing the roof, then reinstalling the panels. That cost and downtime comes straight out of the savings the system was meant to deliver.
Putting new panels on a tired roof is a false economy. A quick roof survey tells you whether you need a repair, a refurbishment or a full re-roof, and what it will cost.
Signs your roof may need work first
- Water ingress or leaks affecting the space below.
- Ageing felt, brittle rooflights or worn roof sheets.
- A fragile roof that installers cannot safely work across.
- Asbestos cement or older cement-fibre sheeting. Our guide to options for asbestos cement roofs covers this in detail.
Not every older roof needs replacing. When a roof is tired but sound, roof maintenance and liquid systems can refurbish it without a full strip-off. Part of the survey is working out which route makes sense alongside solar.
The combined approach
A roof replacement is the ideal moment to add solar. Because our roofing and energy teams sit in the same group, we can deliver both in one coordinated programme.
One programme, one mobilisation
Our roofing and energy teams plan the work together, sharing access and scaffolding instead of mobilising twice. The new roof is engineered to carry the panels from the outset, rather than having an array retrofitted to whatever is there.
No grey area at the interface
Two contractors means two warranties, with a grey area where they meet. If a leak appears around a panel fixing, is it a roofing problem or a solar problem? Industrial solar can compromise a roof warranty, which is why that question matters. With one group responsible for both, there is no dispute over who is responsible for the roof and panel interface.
One point of contact
If anything ever needs attention, there is one team to call for the whole life of the roof and the array.
The combined 30-year warranty
When Cornerstone fits your new roof and installs your solar, both are covered by a single combined 30-year warranty from Cornerstone. The condition is important: the combined warranty applies when Cornerstone fits the roof and installs the solar system. Ask us for the full terms. Our article on the combined roof and solar 30-year warranty explains it further.
What it looks like on real projects
Booker Watford
Booker's existing roof was due for replacement, which made it the ideal moment to integrate solar. A new weather-resistant roof engineered to carry the panels went on with a 334 kWp array as one job, through a partnership between Cornerstone (solar) and NWIR (roofing). Both roof and system carry a 20-year warranty, and the project achieved a 3.1-year payback. Read the Booker Watford roof and solar case study or our Booker Watford project spotlight.
Lovania Nurseries
Lovania wanted solar, but traditional installers could not work across its ageing, fragile cement-fibre packing-house roof, with machinery running directly below. Our solar and roofing divisions sized a 50 kW array and its financial return, then devised an out-of-hours roof replacement schedule to create a secure base for the panels, with no disruption to the nursery's operations. See the Lovania Nurseries case study.
Does re-roofing hurt the payback?
A new roof adds cost, but the comparison that matters is against doing the roof later with panels already in place. We can also fold the roof and the solar into a single finance package (CAPEX, lease-to-own or a green loan) that is offset from day one by your energy savings. Typical payback on our commercial solar schemes is around two to four years, and our guide to commercial solar payback explains what moves that figure.
The new roof brings its own benefits too. A re-clad or over-clad roof can be insulated for a warmer, drier, more efficient building, and rooflights can be renewed. Our roof cladding team installs twin-skin, composite and single-skin systems.
More from the project
Talk to us
If your roof is due for attention and you are considering solar, we can survey both together and give you one plan. Tell us about your site or call us on 0800 011 9758.
Power your business with solar.
Our renewables team designs, installs and maintains commercial solar, storage and EV charging across the North West and the UK.