Drone roof survey in Tavistock

Tavistock is architecturally distinctive because it was rebuilt in the nineteenth century on copper wealth, in green Hurdwick stone, to a deliberate plan. The result is a town centre of substantial Victorian buildings with steep slate roofs, tall stone chimney stacks and a lot of decorative detail up at roof level that nobody has looked at closely in a long time.

Tall stacks on tall buildings are the specific concern. A stone or brick stack standing well proud of the ridge takes serious wind loading, and the mortar in the joints and the flaunching around the pots is doing structural work. When flaunching cracks, water gets into the stack and starts taking it apart from the inside.

Delabole and Cornish slate is common here, which is durable but heavy, and a heavy covering makes any structural movement in the roof below more consequential.

Tavistock sits in the Tavy valley with Dartmoor on one side and the Tamar valley falling away west towards Cornwall, and the prevailing south-westerly brings rain straight up it. This is one of the wetter towns in the dataset and the roofs show it.

Persistent damp means the town's slate roofs carry substantial lichen and moss, particularly on north-facing slopes and in the valleys between the ranges of the larger buildings. On a heavy slate roof, a valley that is packed with growth is holding a lot of water in exactly the place you least want it.

The steep ground either side of the town adds turbulence to the wind, so the exposure on any given property depends heavily on where it sits in the valley rather than on how tall it is.

Outside the town, the villages that grew up around the mines are rows of small terraced cottages, often rendered or slate hung on the weather elevation because that is what the exposure demanded.

Slate hanging on a wall is worth surveying in its own right. It is a weatherproofing layer rather than a decorative one, and when slates start slipping off a hung elevation the wall behind begins taking driving rain directly. It is also almost impossible to inspect properly from the ground because you are looking at it edge on.

The whole area sits within the Cornwall and West Devon Mining World Heritage Site, which means a proportion of the building stock is listed or in a conservation area, and a survey that touches nothing at all avoids a conversation nobody wants to have twice.

The Pannier Market and the buildings around it sit at the centre of the same green stone town, and market buildings of that era typically carry wide span roofs over the trading floor with far less pitch than the housing around them. A shallow span roof over a public building is a different survey again: less about individual slates and more about the long runs of valley and box gutter that a market hall roof relies on to shed water quickly.