Most loft conversions in London do not need planning permission. They are covered by permitted development rights, which means you can build without a planning application, as long as your project stays within the limits. This guide explains the rules, when they do not apply, and what else you need in place before you build.
When you do not need planning permission
A loft conversion is usually permitted development if it meets all of the following:
- The added roof volume is no more than 40m³ for a terraced house or 50m³ for a semi-detached or detached house.
- It does not extend beyond the plane of the existing roof slope that faces the road.
- It is not higher than the highest part of the existing roof.
- The materials are similar in appearance to the existing house.
- There are no verandas, balconies or raised platforms.
- Any side-facing windows are obscure-glazed and non-opening below 1.7m.
Under these rights, a standard rear dormer or a hip-to-gable conversion on a typical London house usually qualifies.
When you will need planning permission
You will normally need a full planning application if any of the following apply:
- Your home is a flat or maisonette (permitted development does not apply).
- Your property is in a conservation area or covered by an Article 4 direction (which removes permitted development rights).
- You want a mansard conversion, which changes the shape of the roof.
- Your project would exceed the volume limits above.
- Your home is listed or in a listed building’s curtilage.
If you are unsure, a quick check of your postcode against your council’s conservation-area maps settles it. We confirm this at the survey stage.
What is a lawful development certificate?
If you are relying on permitted development, you can apply for a Lawful Development Certificate (LDC). It is not compulsory, but it is a formal record that your conversion was lawful, which is useful when you come to sell. Councils charge a fee for the application.
Building regulations always apply
Whether or not you need planning permission, every loft conversion needs building regulations approval. This covers the structure, fire safety, insulation, means of escape, electrics and drainage. Building control will inspect the work at set stages and issue a completion certificate at the end. A conversion built without it can be difficult to sell.
The Party Wall etc. Act 1996
Loft conversions on terraced and semi-detached homes usually affect a party wall or party structure, which brings the Party Wall etc. Act 1996 into play. You must serve notice on the adjoining owner before work starts. This is routine, and we explain it in detail in our guide to party wall agreements.
How we help
LET-HD Developments manages the whole process for you, including the drawings, structural calculations, the building control application and any planning application. We tell you clearly at the survey stage whether your project needs permission. You can read more about our loft conversion service.
Frequently asked questions
How long does planning permission take?
A householder planning application is usually decided within eight weeks, though some London boroughs take longer. Permitted development needs no application at all.
Can my neighbour stop my loft conversion?
Not by refusing planning permission alone, but the Party Wall etc. Act gives them rights over work affecting a shared wall. In practice, the vast majority of notices are agreed without dispute.
Do I need an architect to apply?
You need accurate drawings. We can prepare them, or work with your own architect if you prefer.
Check whether your loft needs permission
Call +44 (0) 203 355 5313 or use our contact form and we will tell you what applies to your property, free of charge.