The permitted development rules for rear extensions
On a house, a single-storey rear extension is permitted development if it projects no more than 3 m from the original rear wall on a terraced or semi-detached house, or 4 m on a detached house, is no higher than 4 m, has eaves no higher than 3 m where it comes within 2 m of a boundary, and uses materials similar in appearance to the house. The larger home extension route allows 6 m or 8 m through a 42-day prior approval, where the council consults the neighbours.
Flats and maisonettes have no householder permitted development rights, so any rear extension to a flat needs planning permission. Previous extensions count against the allowance, and the larger home extension route is not available in conservation areas.
What changes in Camden
In a conservation area a single-storey rear extension can still be permitted development within the 3 m or 4 m limit, but cladding it in materials that differ from the house is not, and the 6 m and 8 m prior approval route is closed.
The local constraints that most often decide the route in Camden are listed below, taken from our Camden area page. Each one is a reason to confirm the address on Camden's constraints map before relying on permitted development.
- Conservation areas. Camden has around 40 conservation areas covering a large share of its housing, including Hampstead, Belsize, Primrose Hill, Bloomsbury, Kentish Town, Fitzjohns/Netherhall and West End Green. Roof extensions are not permitted development inside them, and each area has a published appraisal and management strategy that officers apply closely. Source
- Listed buildings. Camden has thousands of listed buildings, concentrated in Bloomsbury, Hampstead, Highgate and Primrose Hill. Listed building consent is needed for almost any alteration, internal or external, in addition to planning permission. Source
- Article 4 directions. Camden has Article 4 directions in a number of conservation areas removing permitted development for front alterations and other works, and a direction restricting Class MA commercial-to-residential conversions in the Central Activities Zone and some town centres. Check the council's constraints map before relying on permitted development or prior approval. Source
What Camden planning officers look for
Camden is one of the more demanding London authorities for householder work. Officers apply the CPG documents closely and pay particular attention to the uniformity of terrace rear elevations, the depth and height of rear extensions relative to neighbours, and roof additions in conservation areas, where a mansard or dormer is often only accepted if it matches an established pattern in the terrace. Front dormers and full-width box dormers are routinely refused. Camden offers a paid pre-application service and we strongly recommend it for anything in a conservation area or involving a basement. Decisions frequently run past the statutory 8 weeks; allow 12–16 weeks.
Fees and timelines
The council fee for a householder application is £528 and for a Lawful Development Certificate £264 (England, from 1 April 2025; verify before applying). Both are decided within 8 weeks of validation.
Our own fee for the drawings and the application is fixed once quoted and depends on the project type, its size and the constraints above. Answer six questions in the quote tool and we email you an indicative figure within minutes, then a written fixed-fee quote within 24 hours.
