Home / Guides / Loft Conversion or Extension Planning Permission
By Salman Yousaf, SY Design Studio · Updated 2026
The short answer: often not, but it depends on the size and shape of what you're proposing, and on your specific property. Most straightforward loft conversions and single-storey rear extensions can be built under permitted development rights — but several common factors remove those rights and mean a full planning application is required instead.
The General Permitted Development Order (GPDO) grants automatic permission for many house extensions and loft conversions, subject to limits on volume, height and how close the works come to a boundary. A typical rear dormer loft conversion, for example, is permitted development provided the additional roof volume doesn't exceed set limits and materials match the existing house.
Permitted development rights are commonly restricted or removed by: an Article 4 direction covering your property; a conservation area designation; the property being a flat or maisonette (permitted development for extensions generally applies to houses, not flats); a previous extension that has already used up the available volume; or a planning condition on your property removing the rights outright.
Some larger extensions sit in a middle category: they need a Prior Approval application, where the council checks specific impacts (like neighbour amenity) but doesn't run a full planning assessment. If your project doesn't qualify for permitted development or prior approval, a full householder planning application is the route, assessed against the NPPF and your council's local plan.
Because permitted development rules interact with your specific property history and local designations, the only reliable way to confirm your position is to check with your local planning authority or apply for a Lawful Development Certificate. We carry out this check as the first step on every project.