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

Topsham is about ten minutes from the base, which makes it one of the few places where a very small job is straightforward to justify on its own. One chimney, one valley, one section of parapet: worth flying, worth quoting, no need to wait for something else in the area.

It is also a town where the survey is often wanted quickly, because a large share of the building stock is listed and a great deal of it is in the hands of owners who want to know what is happening up there before a builder starts guessing.

The historic core is a dense run of merchant houses and cottages, many of them listed, built right up to the water and right up to each other. Behind them are Victorian and Edwardian streets and then modern infill towards the Exeter road, but it is the old core that generates the survey work.

The problem is geometry. Buildings this tight have shared valleys, party wall abutments, hidden gutters behind Dutch influenced gables, and lead and zinc detailing that has been patched by several generations of different trades. None of it is visible from the street and most of it is not visible from a neighbour's window either. Scaffolding a listed frontage to find out whether a lead flat has failed is an expensive way to ask a question.

The Dutch influenced gables are a specific case worth naming. A gable of that shape has more edge, more upstand and more lead per square metre than a plain one, and every one of those junctions is a place water can be persuaded to go the wrong way. From the air they photograph beautifully and read clearly.

The estuary is damp and salt laden the whole year round, not just in storms, and the town takes the full run of wind up the water from the south. That combination drives rain hard against south west facing slopes and puts salt on every fixing.

In practice the fixings go before the coverings. Slate here is often perfectly serviceable while the nails holding it have rusted to nothing, which is why a slate that has slipped in Topsham is a signal to look at the whole slope rather than an isolated repair. Clay pantile behaves differently again: it is a big unit with a shallow lap, and hard driven rain from the south west finds its way under a pantile that a gentler climate would never trouble.

Lead and zinc detailing corrodes and creeps in these conditions, and both show well from above. Splits at the fold, lifted welts, and lead that has crept down a valley far enough to open a gap at the head are all photographable at a distance that makes them readable in a report.

Topsham has open water, salt marsh and mudflats on three sides, and a lot of birds. The wind coming up the estuary arrives in gusts rather than as a steady flow, and it changes character as it comes round buildings on the Strand. A flight here gets planned with more margin than the same job would need inland.

The Goat Walk, Bowling Green Marsh and the quay are all places where the ground next to a property is public and busy in good weather. Where an address backs onto one of those, the sensible answer is often an early start rather than a clever flight plan.