# Loft conversions in Hillingdon

Canonical URL: https://mirion.uk/areas/hillingdon/loft-conversions/

> Loft conversions in Hillingdon: rear-only roof extensions, the two-thirds width rule, hip-to-gable limits and traditional dormers in conservation areas.

We convert lofts across Ruislip, Eastcote, Ickenham and Northwood, where Hillingdon's policy sets clear limits on the size and shape of roof extensions.

### Hillingdon's roof policy

Policy DMHD 1 says roof extensions should:

- be on the rear elevation only;
- be subservient to the existing roof and no more than two-thirds of its average width;
- sit below the ridge and keep a substantial part of the original roof slope above the eaves; and
- use materials and details that match the house.

The council will not support over-large roof extensions, including converting a hipped roof to a gable, and raising the main ridge will generally not be supported. Its supporting guidance adds that, as a guide, roof extensions should not cover more than a third of the main roof, and that dormers should be no larger than the first-floor windows. In conservation areas and Areas of Special Local Character, roof extensions must be traditional rear dormers, kept well within the roof slope.

### Permitted development is often the practical route

Because the policy is strict, hip-to-gable and full rear dormer conversions in Hillingdon are usually only achievable under permitted development: up to 50 cubic metres on a semi-detached or detached house. Check that your house keeps its rights, and consider a lawful development certificate. Either way, any new side-facing windows should be high-level, obscure-glazed and non-opening below 1.8 metres above the floor under Hillingdon's guidance.

Hillingdon loft conversions: common questions

Will Hillingdon approve a hip-to-gable loft conversion?

Not through a planning application in most cases: policy DMHD 1 lists converting a hipped roof to a gable among the roof extensions the council won't support. If your house keeps its permitted development rights, it may be possible without an application.

Can I have a front dormer in Hillingdon?

No. Hillingdon's Local Plan says only rear roof extensions and rear dormer windows are considered acceptable.