Service
Loft Conversions
A loft conversion turns the unused roof space of your home into a usable bedroom, office or bathroom. AVA Home Design designs dormer, L-shaped dormer and mansard conversions across London and the Home Counties, from feasibility and planning through to technical drawings and the build.
A loft conversion is usually the most cost-effective way to add a bedroom to a London or Home Counties house. Many fall within permitted development, which means no full planning application is needed.
We design loft conversions that pass building regulations on staircase headroom, fire escape and insulation, and that look right from the street.
Types
- Dormer
- A flat-roofed box dormer at the rear, maximising standing-height floor area. The default solution for terraces and semis.
- L-shaped dormer
- A dormer that wraps over the rear and the side return, usually with enough floor area for a bedroom plus en-suite.
- Mansard
- A full reshaping of the roof into a near-vertical rear face. Gives the most floor area but always needs full planning permission.
- Hip-to-gable
- Combined with a dormer to convert the hipped end of a semi or end-terrace into a usable room. Usually permitted development.
Frequently asked questions
- Do I need planning permission for a loft conversion?
- Most dormer, hip-to-gable and L-shaped dormer conversions are permitted development on houses (not flats), provided the volume of the loft addition stays within 40 cubic metres for terraces and 50 for semis and detached, the addition does not extend beyond the existing roof slope at the front, and the materials match the existing house. Mansard conversions and houses on designated land always need full planning. We assess this on the first call.
- How much headroom do I need for a loft conversion?
- Building regulations require a minimum 2m headroom over at least the centre two-thirds of the staircase, and there must be enough usable floor-to-ridge height to make the room worth having, typically 2.3m or more under the existing ridge. We measure this on survey.
- How much does a loft conversion cost?
- Construction costs in London typically run from around £40,000 for a Velux conversion to £60,000 to £90,000 for a dormer or L-shaped dormer, depending on specification. Mansards cost more. We quote design fees as a fixed price after the first call.
- How long does a loft conversion take?
- Design and planning take 6 to 10 weeks if it qualifies as permitted development, longer if a full application is needed. Construction is typically 8 to 12 weeks for a dormer.