Usually no — most loft conversions qualify as Permitted Development if under 40m³ (terraced) or 50m³ (semi-detached), with 20cm eaves setback and matching materials. Flats, listed buildings, and conservation areas need full planning.
Usually not. Most London loft conversions are permitted development, within a volume allowance of 40 m³ for a terraced house or 50 m³ for a semi-detached or detached one. You do need permission in a conservation area, on a flat or maisonette, on a listed building, or where an Article 4 direction or a planning condition has removed the right.
Class B of the GPDO permits a roof extension adding up to 40 m³ on a terrace and 50 m³ on a semi or detached house. The extension must not exceed the highest part of the existing roof, must not extend beyond the plane of any roof slope fronting a highway, must be set back at least 200 mm from the original eaves, and must use materials similar in appearance to the existing house.
Side-facing windows must be obscure-glazed and non-opening below 1.7 m. Balconies and verandas are excluded outright — a Juliet balcony within the plane of the roof is normally acceptable, a projecting one is not.
In a conservation area or on Article 2(3) land, where Class B is withdrawn entirely. On a flat or maisonette, which have no householder permitted development rights at all. On a listed building, where listed building consent is also needed. Where an Article 4 direction applies. And where a condition on the original planning permission removed permitted development rights — very common on estates built since the 1980s.
A mansard almost always needs permission too, because it exceeds the existing ridge and alters the roof slope facing the street.
Yes. The 40 or 50 m³ is measured against the original roof — the house as first built, or as it stood on 1 July 1948. A previous owner's dormer consumes part of the allowance, and a hip-to-gable counts toward it as well as the dormer itself.
With a Lawful Development Certificate: £274, determined in eight weeks. It is not compulsory, but where the volume sits near the limit it converts a judgement into a binding decision, and conveyancing solicitors ask for it on sale.
How do i need planning permission for a loft conversion? plays out in Merton: London Borough of Merton (Merton Council) maintains 28 conservation areas, the Wimbledon Village Conservation Area and the John Innes Conservation Area among them, and there is no borough-wide Article 4 direction, so permitted development generally survives outside conservation areas. Anyone dealing with do i need planning permission for a loft conversion? at a Merton address is therefore working to a £548 householder application decided in 8 weeks, or a £249 prior approval over 6 weeks where do i need planning permission for a loft conversion? still qualifies. are the Town and Country Planning Act 1990, the GPDO 2015 and the Building Regulations 2010.
| Volume allowance, terrace | 40 m³ |
|---|---|
| Volume allowance, semi or detached | 50 m³ |
| Set-back from eaves | 200 mm |
| Conservation area | Permission required |
| Lawful Development Certificate | £274, 8 weeks |
| Our loft drawing package |
Not usually outside a conservation area, provided the volume and set-back limits are met.
Not under permitted development. Flats and maisonettes have no householder rights, so a full application is required — plus the freeholder's consent.
Eight weeks from validation, the same as a householder application.
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