Planning a loft conversion: the first questions

Most loft conversations start with a picture of a bedroom. The useful start is duller: can you stand up, and can a stair land without wrecking the floor below?

Head height

Measure from the top of the ceiling joists to the underside of the ridge. Building control wants a sensible amount of standing room over the stair and in the main part of the room. If the ridge is low, a dormer or a mansard is doing structural work, not just adding a window.

The stair

The stair needs a going and a head clearance that pass the rules, and it needs somewhere to start. A landing that is already tight will feel worse once a new flight arrives. We look at that on the first visit, before anyone draws a dormer.

The roof shape

• A simple rear dormer suits many terraces.
• A hip-to-gable is for houses with a sloping side roof.
• A mansard changes the whole roof and usually needs planning permission.

None of this is a quote. It is the short list we use so you do not pay for a design the house cannot hold.