Planning in a London conservation area

Check the house before the design

Four questions decide the route. Is the house in a conservation area? Is there an Article 4 direction covering it? Is it listed? And is it still a single house, or has it been converted into flats? The first three are on the borough’s planning map; the last is on the title. Flats have no householder permitted development rights, and a listed building needs listed building consent for almost any extension.

What changes in a conservation area

Conservation areas are designated by the borough to protect the character of a street. For extensions, the rules tighten in three ways:

• Side extensions are not permitted development, so side returns and wraparounds need a householder application (£548).
• The larger home extension scheme, which allows a 6 metre rear extension on a terrace after prior approval, does not apply.
• Cladding any part of the outside in stone, render, timber, plastic or tiles is not permitted development. That matters for modular extensions, which are often clad in timber or composite boards.

A plain single-storey rear extension within the 3 metre limit, finished in brick to match, can still be permitted development. Get a lawful development certificate (£274) before the factory starts.

Article 4 directions

An Article 4 direction removes particular permitted development rights over a defined area. In London they are often used in conservation areas to protect front elevations, windows, doors and roofs, but some cover rear extensions too. Each borough publishes its directions with a map and the list of rights removed. If your street has one that covers rear extensions, you need a full application even for work that would otherwise be allowed.

How the borough type changes things

Inner boroughs with dense Victorian terraces such as Islington, Hackney, Lambeth, Camden and Kensington and Chelsea have a large share of their streets in conservation areas. Expect a householder application for most side returns and wraparounds, and a conversation about materials.

Outer boroughs with interwar semis such as Bexley, Havering, Hillingdon and Sutton have fewer conservation areas and more side access. Permitted development is more often available, and a crane is not always needed.

Mixed boroughs such as Ealing, Lewisham, Wandsworth and Haringey switch from one to the other street by street. Look up the address, not the borough.

Materials for a modular extension

Planning officers in conservation areas are mostly interested in what the extension looks like from the street and from neighbouring gardens: its height against the boundary, the roof form and the facing material. A modular structure can be finished in brick slips to match London stock, in dark standing-seam metal, or in timber where the officer accepts it. Ask the builder for a materials sample to submit with the application.

A pre-application enquiry costs a fee in most boroughs but can save a refusal; it is worth it for a wraparound in a sensitive street.