House Extensions in Highgate (N6)

The borough boundary runs along Highgate High Street. East of it, you're in Haringey; west of it, Camden. The two councils have different local plans, different conservation officers and different validation checklists, so a scheme drawn for one side can't simply be carried across the line.

The Haringey side. The village's eastern half, Southwood Lane, Cholmeley Park and the slopes down to the Archway Road sit in Haringey's Highgate conservation area, designated in December 1967. Haringey's list of conservation-area Article 4 directions doesn't include it, so the national conservation-area rules are the working constraint: no side extensions, dormers or larger-home prior approvals without planning permission.

The Camden side. West of the High Street, Camden's own Highgate Village conservation area covers the old village, with the Holly Lodge Estate and Dartmouth Park conservation areas further down the hill. Across the whole of Camden, an Article 4 direction confirmed in October 2016 restricts basement extensions, so a basement on this side needs planning permission from the start.

The edges. N6 isn't only Haringey and Camden: postcode records put some N6 addresses in Islington and Barnet too. We confirm the deciding council from your address before any design work, and our North London borough guide sets the councils' rules side by side.

On the Victorian terraces and semis between Cholmeley Park and the Archway Road, the kitchen typically sits in a narrow back addition with a strip of side passage running beside it. A glazed side-return extension infills that passage and turns a galley kitchen into a full-width kitchen-diner without giving up any garden. The catch in N6 is the conservation area: side extensions are not permitted development on conservation-area land, so wherever the Highgate conservation area covers your street, the side return needs a planning application. Beyond its boundary, a modest single-storey side infill can often go ahead under permitted development.

On detached and wider semi-detached houses the kitchen more often moves to the rear. Inside the conservation area the larger home extension route under prior approval isn't available, so a deep rear kitchen goes to a full application and is judged on how it sits against the house and its neighbours. On a listed village house, Listed Building Consent comes on top, and the heritage statement has to justify every new opening made in historic fabric.

For layouts, glazing and how the old kitchen is kept working during the build, see our kitchen extensions guide. The cost table below carries a kitchen-extension line that includes a mid-range kitchen.

Which side of the High Street you live on decides how a basement is handled. West of it, Camden's borough-wide Article 4 direction, in force since 1 June 2017, means every basement or lightwell excavation needs planning permission, and Policy A5 of its Local Plan limits a basement to one storey and half of each garden. East of it, Haringey applies Policy DM18, which asks for a Basement Impact Assessment showing the dig will not harm neighbouring buildings, raise flood risk or damage garden trees. On both sides the Highgate Neighbourhood Plan adds Policy DH7: no damage to neighbours beyond Burland Scale 1, and at least a metre of permeable soil over any basement beneath a garden. Both Highgate wards saw basement approvals in the twelve months to 22 September 2026, among them North Road and Sheldon Avenue on the Haringey side and Fitzroy Park and Hillway on the Camden side, and our basement conversions in North London page covers the engineering, the party wall process and typical London costs.

Highgate's larger houses can carry a much bigger brief: double-storey reworks behind Georgian and Victorian fronts, basements under the hill, whole houses reorganised around light and garden. Once a brief reaches whole-house scale it changes category, and the design and consent strategy should change with it.

That category is served by our large and luxury extensions offer, priced fixed and banded honestly in the luxury extension cost guide.