Loft conversions in Lambeth depend on the house. Typical homes here: Georgian and early Victorian terraces in Kennington, Stockwell and Clapham Old Town; Victorian terraces in Brixton, Herne Hill, Clapham and Tulse Hill. Designations to check first: Conservation areas; Article 4 directions; Thames flood zones. Applications are decided by London Borough of Lambeth and the Lambeth Local Plan 2021.
The permitted development rules for loft conversions
A loft conversion with a rear dormer is permitted development on a house if the added roof volume is no more than 40 m³ on a terraced house or 50 m³ on a semi-detached or detached house, the dormer sits at least 200 mm back from the eaves and no higher than the ridge, there is no dormer on the roof slope facing the road, materials are similar in appearance, and side windows are obscure-glazed.
Flats and maisonettes have no permitted development rights, so a loft to a top-floor flat always needs planning permission. Full-width box dormers that reach the ridge, and hip-to-gable conversions on semis whose volume exceeds 50 m³, also fall outside the allowance.
What changes in Lambeth
Roof extensions are not permitted development in a conservation area, so a dormer or hip-to-gable there needs a householder planning application designed to the area's appraisal.
The local constraints that most often decide the route in Lambeth are listed below, taken from our Lambeth area page. Each one is a reason to confirm the address on Lambeth's constraints map before relying on permitted development.
- Conservation areas. Lambeth has numerous conservation areas covering much of Kennington, Stockwell, Clapham, Brixton, Herne Hill and Streatham. Source
- Article 4 directions. Lambeth has Article 4 directions in a number of conservation areas removing permitted development for front alterations and boundary treatments, and a Class MA Article 4 covering Waterloo, Vauxhall and other central and town-centre locations that removes the commercial-to-residential prior approval route.
- Thames flood zones. Waterloo, Vauxhall, Nine Elms and the riverside at Lambeth fall within Flood Zones 2 and 3, protected by the Thames Barrier and river walls. Source
- Listed buildings and the Kennington and Clapham set pieces. Kennington, Clapham Old Town, Stockwell and the Vauxhall riverside contain many listed Georgian and Victorian houses and terraces.
- Metropolitan Open Land. Clapham Common, Brockwell Park, Streatham Common and Norwood Park are Metropolitan Open Land.
What Lambeth planning officers look for
Rear extensions deeper than neighbouring precedent, side returns that breach the 45-degree rule to the neighbour's rear window and roof extensions in conservation areas are the common refusal reasons. Mansards are accepted on terraces where the street already has them; front dormers and roof extensions on butterfly-roofed terraces attract resistance. Pre-application advice is available for a fee, and Lambeth's decision times can stretch beyond the statutory period at busy times.
Fees and timelines
Lambeth decides a householder application or a Lawful Development Certificate within 8 weeks of validation. The council fee is £528 for a householder application and £264 for a Lawful Development Certificate (England, from 1 April 2025; verify before applying).
Our own fee is fixed once quoted. The quote tool gives an indicative figure in minutes and a written quote follows within 24 hours.
Primary sources
- The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2: the permitted development limits quoted above.
- Planning Portal: do you need permission: the national guidance and the application service every council accepts.
- London Borough of Lambeth: planning: the council's own constraints map, validation checklist and pre-application service.
