Should You Have the Roof Checked Before Solar Panels?

Why the roof matters more than people expect

Solar panels are fixed to the roof structure with brackets that pass through the covering. Each fixing is a hole to seal, and each panel adds weight and catches the wind. If the tiles under them are cracked, the battens are rotten or the underlay has perished, the panels sit on a weak base and the water finds its way in around the brackets.

The cost of getting at the roof later is the bigger issue. To replace a tile or repair a flashing beneath an array, the panels must be disconnected and lifted off by an installer, and then put back and tested. That is a separate bill on top of the repair. It makes sense to deal with the roof first.

The age of the roof counts. If the covering is near the end of its life, it can make more sense to re-roof before the panels go on, or to look at integrated systems. Our page on re-roofing with in-roof solar explains that route.

Weight is part of this. A typical array adds a modest but continuous load on the rafters, and wind can push and pull on the panels with surprising force. Rafters that are old, thin or split need to be checked before anything is fixed to them. Brackets are only as strong as the timber they bite into.

What a roof check covers

We start with the outside. We look at the condition of every tile or slate, the ridge and hips, the verges and eaves, and the flashings round chimneys and dormers. We check the gutters and fascias, because a panel array alters the way rain runs off a roof.

Then we go into the loft. We look at the rafters and battens for rot, sag or damage, at the underlay for tears and at the insulation and ventilation. The structure has to carry extra load, so we note any sign of movement or undersized timbers. We do not give a structural engineer's design, but we flag anything that should be checked by one.

We photograph what we find and give you a plain written finding, which you can hand to the solar installer.

Orientation and shade are the installer's concern, not ours, but the roof check can still help. If we see that a slope is shaded by a chimney, a tree or a dormer, we mention it, since it affects where panels sit and which tiles need to be lifted.

The finding is written so that a non-roofer can follow it, and the photographs are labelled by slope.

What can go wrong if the check is skipped

Skipping it can mean panels fixed over slipped or broken tiles, bracket holes through weak battens and a leak that appears a year or two later. By then the cause is hidden under an array. The installer may point to the roof, the roofer may point to the installer, and you are in the middle.

A check also gives you the order of work. If repairs are needed, they are done first, then the panels follow. If the roof is sound, you proceed with confidence and a record of its condition at the date of installation. That record can matter later if there is a dispute.

Roof windows, vents and chimneys also need thought. Panels should clear them, and shading from a chimney can affect output. A roofer can tell you what is practical on the slope.

Think about access, too. Panels get cleaned, serviced and sometimes replaced. A roof with a steep pitch, fragile rooflights or no safe route to the ridge needs a plan for how people will get up there safely in years to come.

Repair, re-roof or leave it

There are three outcomes. The roof may be fine, in which case the panels can go on. It may need a modest repair, which we do before the installers arrive. Or it may be near the end of its life, in which case a re-roof first, or a combined re-roof and solar job, makes more sense than panels over a failing surface.

We say which applies, and we do not suggest work the roof does not need. Where repair works, we repair. A fixed written quote follows the free survey. Details of the service are under roof inspections in Basingstoke.

Ask the installer to put roof-side details in the quote: how many brackets, what sealing is used and who is responsible if a tile cracks during fitting.