Drone survey in Exeter

Exeter is unusual in how many different kinds of building sit within a few streets of each other. The older central quarters carry Georgian and Victorian terraces with natural slate, party walls and hidden valleys. The outer ring is post-war semis and estates under concrete interlocking tile. Around the university there are large blocks of purpose-built student accommodation with flat roofs and plant on top of them, and out towards Pinhoe the newest housing is barely finished.

Each of those has a different failure pattern, and a first survey is worth more when it starts from the right one. On a Victorian terrace the questions are usually about the valley between two pitches, the state of the party parapet and whether the front slates are original. On a 1970s estate house they are about ridge mortar, verge pointing and a flat roof over a back extension that nobody has looked at since it was built.

The city sits on a low ridge above the tidal head of the Exe, with the ground dropping east into the Clyst valley and climbing west towards Haldon. Rainfall here is above the England average, and the valley holds damp air rather than letting it move through. The practical result is that north-facing slopes dry slowly and organic growth is persistent.

Moss is not automatically a problem, and a survey that treats every patch of it as a defect is not helping anybody. What matters is where it is holding water: in the laps of a slate roof it lifts the tail and lets water track backwards, and in a gutter or a valley it turns into a dam. A set of photographs from above shows the difference between a green roof and a blocked one, which is the thing you cannot judge from the pavement.

Most Exeter addresses are straightforward to fly. The complications are ordinary urban ones: finding a few square metres of clear ground to take off from on a street with no front gardens, working over a terrace where the neighbours are three metres away, and picking a time of day when a school run is not passing the gate.

The one specifically local factor is Exeter Airport, which sits east of the city near Clyst Honiton. Addresses close to it need the airspace question settled before a date is offered rather than on the morning. That is a planning matter and it is not usually an obstacle, but it is the reason an EX5 job near the runway takes longer to book than an EX4 job in St Thomas.

Exeter has a large rented and managed sector, so a good share of the enquiries come from landlords and managing agents who need to know the condition of something they do not live in. A dated photographic record of a roof is worth having on a file for exactly that reason, and it settles arguments about when a defect appeared.

The other big use is the stalled sale. The city moves a lot of property, and a buyer's survey flagging a roof is one of the commonest reasons a sale sits still. Photographs of the actual roof, taken this week, generally move it one way or the other inside a fortnight.