House extension in Arkley

Connect the added space to the existing home.

Start with the house extension brief

Begin with how the new space will meet the old rooms, garden and circulation. A measured brief should record boundaries, levels, existing drains, neighbouring windows and the parts of the building you intend to keep.

Develop daylight, structure and services alongside the floor plan. Agree which openings and finishes are included, how the existing home will be protected during construction and which decisions need surveys or approval before a quotation.

The local building context

Planning data places Arkley Windmill, Arkley War Memorial and the mapped points of many Arkley tree preservation orders in the London Borough of Barnet and its High Barnet ward. Arkley sits on the county boundary with Hertsmere, in Hertfordshire. In 1959 it lay in the Urban District of Barnet, then part of Hertfordshire, and a boundary order made in 1992 moved land both ways from 1 April 1993: its explanatory note says part of Arkley Lane went to Hertsmere, while housing development north-west of Whalebone Park came into Barnet.

Historic England’s list, as planning data records it, includes Arkley Windmill at Grade II*, list entry 1359022, the barn in its grounds at Grade II, Arkley War Memorial at Grade II and the Grade II Church of St Peter, mapped beside the memorial. Elm Farmhouse and adjoining barn, Grade II, is mapped near Galley Lane, and Trinders Lodge and Hyver Hall, both Grade II, are mapped elsewhere in High Barnet ward, inside the Green Belt record. Listing is recorded entry by entry, so read the entry for the exact building.

Neither the name Arkley nor an EN5 postcode tells you which council decides, whether land is in the Green Belt or a conservation area, whether a building is listed, which Article 4 direction reaches it or which consent route the work takes. The 1992 boundary order’s explanatory note says part of Arkley Lane went to Hertsmere, so confirm the council with the official lookup, then read the conservation area and Green Belt records, the list entry, the Article 4 directions and their mapped areas, the title or lease and the planning history of the property.

Local design and consent context

Barnet’s Wood Street Conservation Area Character Appraisal Statement, adopted in July 2007, describes that area running east to west from the top of Barnet Hill along the ridge towards Arkley and including Wood Street itself westward as far as The Whalebones; it was designated in 1969 and extended in 1979. The appraisal notes that the historic county boundary runs through this part of the borough, with Wood Street a peninsula of Hertfordshire cutting eastward into Middlesex. Wood Street is a neighbouring designation, not an Arkley one.

Barnet has 15 Article 4 directions on planning data. Apart from two, each is for a named conservation area, none of them Arkley, and none of those is mapped at the points of Arkley’s listed landmarks or of the many Arkley-area tree orders we checked. Barnet’s direction on small houses in multiple occupation, in planning data from 29 May 2016, does cover those points, but it withdraws only the permitted development right in Part 3 Class L, for changes between a house and a small house in multiple occupation, and does not concern building works.

The National Planning Policy Framework, published on 17 August 2026 and last updated on 29 September 2026, replaces the December 2024 and earlier versions. It treats development in the Green Belt as inappropriate unless it falls within one of the categories in policy GB7, and inappropriate development should not be approved except in very special circumstances. The categories include the reuse, extension, alteration or replacement of a lawful building of permanent and substantial construction, provided an extension or alteration does not result in a disproportionate increase in size over the original building, as it stood on 1 July 1948 or as first built if later, and a replacement is for the same use and not materially larger.

Access and site planning

Plan where deliveries stop, where waste waits and how any shared drive or entrance is protected before work starts. A skip on a public road needs a council licence, which in most areas the skip hire company obtains, while a skip entirely on private land needs none; scaffolding or hoarding on a public highway needs a licence from the local authority, so confirm which council covers the road at the address. TfL licenses such items only on its red routes, so check whether the road outside is one, and on Galley Lane keep vehicles and materials clear of the protected trees on the roadside verge.

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The Arkley area guide · House extension across London · Hampstead Architecture & Planning · Hampstead Chartered Surveyors

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