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

Ivybridge is about fifty minutes from Exeter on the A38. It has a small historic core around the old bridge and mill, but it is overwhelmingly a late twentieth century commuter town: large estates of the 1970s through the 1990s, plus continuing new development.

That makes it unusual on this list. Most of the towns here generate survey work because their buildings are old. Ivybridge generates it because its buildings are young enough that the original specification is still the thing under test, and old enough that the first generation of coverings and details is now reaching the end of its service life.

The town sits on the Erme at the southern edge of Dartmoor, where the moor drops steeply to the South Hams, so the northern streets sit noticeably higher than the southern ones. The moor edge position means high rainfall and strong gusting winds funnelled down the Erme valley.

Put those two facts together and you get the defining survey issue here: mechanically fixed ridge and verge details matter more in this town than in sheltered ones. A dry ridge system that is correctly fixed will sit out a gale. A mortar bedded ridge on an exposed northern street in Ivybridge is on a shorter clock than the same detail would be in Ottery St Mary.

Concrete interlocking tile dominates the estates, with natural slate on the older stock, fibre cement slate in places, and flat roofs on garages and extensions. Fibre cement is worth flagging: it weathers to look like natural slate from a distance and behaves nothing like it, so identifying which is which is part of the job and needs a close frame.

An estate built over two or three years to one specification is the ideal candidate for aerial survey, and for the same reason as the railway terraces at Newton Abbot: what is true of one house is usually true of its neighbours.

For a landlord, a management company or a group of owners, flying several properties in one visit gives a comparative picture that a single inspection cannot. It shows whether a fault is a one off or a pattern, and it puts a number on how many roofs are in which condition.

Flat roofs on garages and extensions are the standing weak point in this stock. They were often the cheapest element of the original build, they are invisible from inside the house, and they are the first thing to fail.

The Erme valley funnels wind, and gusting is the characteristic rather than steady strength. For flying that means margin: an aircraft holding position beside a roof in gusty air is working, and the imagery shows it if the conditions are pushed too far.

The viaduct and the Two Moors Way mark the northern edge of the town, and beyond them is open moor. As at Okehampton, the local forecast is the one that counts and it can differ sharply from Exeter forty five minutes away.