What can't a drone roof inspection detect?

Battens, underlay, decking and structural timber are all hidden by the covering that is being photographed. A roof can look sound and have failed underlay or wet rafters beneath it, and the reverse is also true — a poor-looking covering may sit above dry, sound timber.

Establishing that requires roof space inspection or opening up.

Nail sickness is the standard example: corroded fixings on an otherwise reasonable slate roof, which produce slipping slates one at a time for years. Imagery may show the symptom — slates that have moved — but confirming the cause needs a component lifted by hand.

Whether insulation or decking beneath a flat roof covering is wet cannot be established from above. That needs a core sample or a moisture survey. This is the limitation most often glossed over, and it matters because it decides between a repair and a renewal.

Wind, rain and poor light restrict flights and image quality. Proximity to obstructions, dense tree cover and confined sites limit how close a drone can safely get. Some locations are restricted under CAA rules for the surroundings.

Where any part of a roof could not be covered, the report should say so plainly. A survey presented as complete when it is not is worse than no survey.

A report that lists what it could not establish is not incomplete — it is telling you where the next pound is best spent if the decision is significant enough to warrant it. Ignoring that list and proceeding on the visible findings alone is sometimes reasonable, but it should be a conscious choice rather than an oversight.

Where the decision involves a large sum, such as a full renewal, closing those gaps with roof space inspection or moisture testing first is usually cheaper than committing to the wrong scope.