Loft conversions and dormers
Lofts. Updated 21 September 2026
A loft conversion with a rear dormer is usually permitted development on a house in England. It must stay within a volume allowance and a short list of design rules.
The limits
| Terraced | Semi-detached or detached | |
|---|---|---|
| Extra roof volume | 40 cubic metres | 50 cubic metres |
- No higher than the highest part of the existing roof.
- Nothing projecting beyond the roof slope that faces the road.
- Dormers set back at least 20cm from the eaves, where practical.
- Side-facing windows obscure glazed, and fixed unless the opening part is more than 1.7m above the floor.
- No balconies, verandas or raised platforms.
- Materials similar in appearance to the house.
Previous roof additions count towards the allowance.
When permission is needed
- Flats and maisonettes.
- Conservation areas, National Parks, National Landscapes and World Heritage Sites.
- Listed buildings.
- Streets covered by an Article 4 direction.
- A front dormer, or anything that raises the ridge.
Building regulations
Building regulations approval is needed for every loft conversion, whether or not planning permission is.
Source: Permitted development rights for householders, technical guidance, Ministry of Housing, Communities and Local Government.
Common questions
Can I convert my loft without planning permission?
Usually, on a house in England. It is permitted development if the extra roof space stays within 40 cubic metres on a terrace or 50 on a semi or detached house, and nothing faces the road or rises above the roof. Building regulations approval is always needed.
What size dormer can I build without planning permission?
The whole roof enlargement, dormers included, can add up to 40 cubic metres on a terrace and 50 on a semi or detached house, and earlier roof additions count. A dormer must not face the road or rise above the roof, and should sit at least 20cm back from the eaves where practical.
What are the rules for dormer loft conversions?
In England: materials similar to the house, no balconies, side windows obscure glazed and fixed below 1.7m, and nothing on the roof slope facing the road. Flats, listed buildings, conservation areas, National Parks, National Landscapes and World Heritage Sites need permission.
Do I need planning permission to change my roof from hip to gable?
Not usually. A hip-to-gable conversion is a roof enlargement, so on a house in England it can be permitted development within the 40 or 50 cubic metre allowance and the other loft rules. On protected land or at a listed building it needs permission.
What is the 10 year rule for loft conversions?
There is no rule for lofts as such. In England, the council can take enforcement action against unauthorised building work for up to 10 years after it is substantially completed. For work substantially completed before 25 April 2024 the limit was 4 years.