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

Totnes is about forty five minutes from Exeter, a hill town at the tidal limit of the Dart with a very steep main street running from the river up to the castle. Rolling South Hams farmland surrounds it.

The dense medieval and Elizabethan core is what generates most of the survey work: slate hung and jettied frontages, Georgian and Victorian streets behind, and modern estates on the outskirts at Bridgetown and Follaton.

Tightly packed historic roofs have many hidden valleys and party wall abutments that trap debris, and that is the defining survey issue in this town. A valley between two buildings of different heights, in different ownership, roofed at different dates, is where leaves, grit and moss collect and where nobody has any incentive or any means to look.

When one of those blocks, the water does not run off the front of the building where somebody would notice. It backs up under the slates and into the wall between two properties, and the first sign is damp on an internal wall that neither owner can explain.

From above, this is simple. The valley is either clear or it is not, and a photograph settles the argument between two owners far better than an opinion does. On a run of buildings, one flight can map every valley and every abutment along the row.

Slate hanging appears here as it does at Bideford and Dartmouth, protecting elevations that take driving rain. On a jettied or timber framed building it is doing an important job, because the wall behind it is not designed to be soaked.

Assessing a hung elevation from the street is difficult because of the angle and because much of it is above the shopfronts. From an aircraft at first floor height and a few metres out, every slate is legible, and so is every patch, every slipped unit and every place where the hanging has been cut about for a later pipe or cable.

Alongside the hanging there is natural slate and clay plain tile on the roofs, and concrete tile on the modern estates at the edges.

Inland and reasonably sheltered, but the valley is damp, so the pattern here is closer to Dartmouth than to the coast: organic growth rather than storm damage, and slow deterioration on shaded slopes rather than sudden failure.

Totnes Castle sits above the town and the Dartington Hall estate lies just outside it. Estate and institutional buildings of that kind bring large complex roofs with lead work and long gutter runs, where a systematic aerial record is the only practical way to get a whole picture in one go.