Solar Panels and Your Roof: What to Sort Out Before and After Installation

What Solar Installation Does to Your Roof

Standard solar PV mounting uses roof hooks that pass through tile holes and fix to the rafters below. Each hook requires lifting a tile, drilling through the batten, and fixing a stainless steel hook to the rafter. The tile is then refitted around the hook shank with a small gap. This gap is typically sealed with EPDM or similar flashing material — but the seal quality varies between installers, and the modification is permanent.

On a roof with nail sickness, the tile-lifting process for solar installation can dislodge tiles that were marginal. On a roof with perished felt, the batten drilling is occurring in a zone where the underlying structure is already compromised. Solar installers are generally not roofers — they assess whether there's enough space for the array and whether the structure will carry the load, but they don't typically assess underlying tile, felt, or batten condition.

What to Check Before Solar Panels Are Installed

Have a free roof survey before committing to solar installation. If the survey identifies nail sickness, perished felt, or inadequate batten depth, addressing these issues before solar installation is significantly cheaper than doing it after. Removing and reinstalling a solar array to address underlying roof problems costs £800–£2,000 on top of the repair work — this can be avoided entirely by sequencing correctly.

Specifically check: tile condition and nail sickness progression; felt condition (particularly at the eaves where it's most accessible); batten depth (the solar hooks need adequate timber to fix into — shallow battens may require replacement); and the condition of the ridge and flashings, which are accessible from the roof during installation and are worth addressing at the same time.

After Solar Installation: What to Watch For

After solar installation, any tile that was disturbed for hook fitting should be checked for correct reseating. If water gets under a tile that wasn't correctly refitted, it will track along the felt and appear as a damp patch internally — and it won't be obvious that the solar installation was the cause. We've attended a number of post-solar installation leak investigations in Aylesbury where improperly refitted tiles were the source.

The roof should be inspected from below (in the loft) during the first significant rainfall after installation. Any new staining or wet areas on the felt in line with the solar array indicate a hook seal or tile refit issue. This should be flagged to the solar installer under the installation warranty before involving a roofer.