For a recent Crownhill loft conversion the feasibility came in at £62k all in, including a small front dormer, a new bathroom and the necessary stair re-routing on the floor below. Final account landed within £4k of that — which is about as well as a take-off-led feasibility can hope to perform.

The line items that needed extra care: the stair location (which determined whether the floor-below bedroom shrank to inconvenient), the existing roof structure (trussed, requiring more steelwork than a cut roof), and the energy-performance compliance route given the substantial loss of existing roof.

Loft conversions vary widely in price; numbers from one neighbour’s project rarely transfer to another’s. Always price the building you have.