Drone surveys in Cullompton, flown by the surveyor who writes them

Cullompton is about twenty five minutes from Exeter, straight up the M5 to junction 28. It is one of the easiest towns to reach in the coverage and a sensible one to pair with Tiverton or Honiton in a single morning.

The town has expanded a great deal, so a lot of the enquiries here are about late twentieth century estate housing and new build, sitting alongside a medieval and Georgian core along Fore Street with thatch in the older lanes.

The historic core is the interesting part. Buildings of this age on a tight street frontage have roofs that have been altered many times, valleys between neighbouring properties, and rear elevations that nobody has seen properly in years because the only access is through somebody's yard.

St Andrew's Church and The Walronds are the landmarks and they represent the two ends of the local historic stock: a substantial church roof with lead, parapets and complex drainage, and a fine merchant house of a kind that appears in the surrounding streets in humbler versions.

Thatch in the older lanes brings the same questions as at Crediton, and the flat valley floor position makes them slightly worse: the town holds damp and frost, so thatch and shaded slate both stay wet longer than the surrounding higher ground.

The volume of late twentieth century estate housing means a lot of concrete interlocking tile laid to a pattern, which surveys efficiently and comparatively. Where somebody manages several properties, flying them together answers questions a single inspection cannot.

The industrial estates carry profiled metal sheet, which is its own category. What matters on a profiled roof is the fixings, the laps, the ridge and eaves details, the rooflights and the gutters, and every one of those is a top surface feature. A visual inspection from inside the building tells you about daylight and about leaks that have already happened; a flight tells you about the ones that have not yet.

The motorway junction on the doorstep is why the estates exist and why the units are there. It also makes the town an easy one to serve at short notice.

A valley floor location holds damp and frost, and frost is the mechanism worth naming. Water in a mortar joint, in the surface of a stone tile, or in the top layer of a thatched ridge expands when it freezes, and repeated cycles break the material apart from the inside.

That is why deterioration on shaded, north facing slopes here outpaces the sunny side by more than a casual look would suggest, and it is why a survey is worth doing at the end of winter rather than in the middle of summer if a decision is going to be made from it.

The Blackdown Hills to the east and rolling Mid Devon farmland to the west give the town its weather. Neither produces the sort of exposure the coast does; the issue here is persistence rather than force.