How long does a loft conversion take?

The honest answer is six to twelve weeks on site, depending on the type of conversion and whether a bathroom is going in. Before that, allow four to eight weeks for drawings, structural calculations and, where needed, planning.

A typical dormer conversion

1. Weeks 1 to 2: scaffold up, roof opened, steels in, dormer framed and made weathertight. This is the noisy part.
2. Weeks 3 to 4: floor joists, dormer cladding, windows and rooflights, staircase opening cut through.
3. Weeks 5 to 6: first-fix plumbing and electrics, insulation, plasterboard, staircase fitted.
4. Weeks 7 to 8: plastering, second-fix electrics, bathroom fit-out if there is one.
5. Weeks 9 to 10: decorating, flooring, fitted storage, snagging and building control sign-off.

What speeds it up

• Decisions made before the start: bathroom fittings, flooring and paint colours chosen
• One firm doing the carpentry, plastering, decorating and clearance so trades are not waiting on each other
• Dry weather in the first fortnight

What slows it down

• Changes once the structure is up
• Discovering the existing roof or chimney needs more work than expected
• Waiting for a supplier delivery nobody chased

A Velux-only conversion with no dormer and no bathroom can be done in six weeks. A large mansard with two bedrooms and a bathroom can run to fourteen. We give a written programme before starting and update it weekly.