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

Exeter is the base, which changes the arithmetic on a small job more than people expect. A single chimney stack in Heavitree or St Thomas is worth flying on its own, where the same job an hour and a half away would sensibly wait to be paired with something else. If the question is small and you are in the city, ask.

It also means the desk check on an Exeter address is quick, because the ground is familiar. What is behind a terrace on a particular street, whether there is anywhere sensible to launch from, and which side of a building the wind comes round are all things worked out on foot rather than from an aerial photograph.

In most of Devon the hard part of a survey is getting to the building. In central Exeter the building is easy and the surrounding population is the problem. Georgian and Victorian terraces through the older quarters sit shoulder to shoulder with pavements, gardens and parking on every side, so almost every take off point has somebody near it who has nothing to do with the job.

That is the constraint the permissions actually bite on. Planning a flight in a packed street is a matter of where the aircraft can be launched, how high it climbs before it moves laterally, and which neighbouring garden it is not going to be over. Some addresses need the survey flown early on a Sunday. A few cannot be flown at all within the rules held here, and that gets said before a date is agreed rather than on the doorstep.

Airspace is the other city question. Exeter is not a free-for-all overhead and the check happens at quote stage rather than on the morning. Where a restriction affects what can be done, it changes the plan or it changes the answer.

Four coverings dominate and each fails differently. Natural slate on the older central stock, where the nails go long before the slate does. Clay double roman on the interwar and Victorian fringes, which sheds a tile when the batten behind it softens. Concrete interlocking tile on the post-war ring, heavy and durable but unforgiving at ridge and verge when the mortar bedding lets go. And felt and single ply flat roofs on extensions, garages, commercial blocks and the purpose built student accommodation near the university, which are the ones that quietly hold water until somebody looks down at them.

That last category is the one a drone changes most. A flat roof on a three storey block is invisible from every window and every pavement, and the first anybody knows about a pond around a blocked outlet is a stain on a ceiling two floors down.

The city's rainfall is above the England average and the valley holds damp air, so north facing slopes here dry slowly and organic growth is persistent. Moss in a valley gutter is not a cosmetic finding in Exeter. It is a blockage waiting for a wet fortnight.

The Cathedral, the Quayside, the University and Marsh Barton are the four bits of Exeter most people picture, and between them they cover the range of survey work the city produces. Historic fabric with complex lead and stone detail. Waterside buildings taking damp off the Exe. Institutional accommodation with flat roofs and plant. And a trading estate full of large span roofs where the rooflights and the parapet gutters are the whole job.

The ground itself matters too. The city sits on a low ridge above the tidal head of the Exe, falling away east towards the Clyst valley and rising west towards Haldon, so two properties a mile apart can be in quite different wind. A survey on the western slopes catches more weather than the same building down by the water.