The short answer
The right loft option depends on the roof shape, planning position, budget and structural design — common choices are a simple dormer, an L-shaped dormer, a mansard, or a hip-to-gable conversion. The Party Wall Act may apply too, especially where steel beams are cut into a party wall or the wall is raised.
Why it matters
Each option differs in cost, time and planning (all figures are broad guides):
- Simple rear dormer — about £30,000 to £40,000, 3 to 4 months, often permitted development; usually the most cost-effective, though less attractive externally.
- L-shaped dormer (common on Victorian outriggers) — about £50,000 to £80,000, 3 to 4 months, often permitted development; more floor area and flexibility.
- Mansard — about £35,000 to £75,000, 4 to 5 months, usually needs planning permission; more attractive with better head height, but more complex.
- Hip-to-gable — about £40,000 to £60,000, 4 to 5 months, may be permitted development (check); useful space, though appearance matters on a semi.
What to do now
- Speak to an architect or designer and obtain structural calculations.
- Check whether planning permission or permitted development applies, and whether you own the loft (important in flats).
- Serve any required party wall notices in good time — often two to three months before work starts so dissent can be dealt with without delay.
Common mistakes
- Choosing an option without checking planning or loft ownership.
- Leaving party wall notices too late and delaying the start.
- Assuming guide costs are fixed quotes rather than broad ranges.
When to call Coburns
If your loft scheme cuts into or raises a party wall, send us the plans and we will handle the notices in good time so they do not hold up the build.