Basement conversion in Stanmore

Investigate the structure and ground before design.

Start with the basement conversion brief

Distinguish an existing cellar conversion from excavation for a new basement. Record levels, drainage, access and the adjoining structures, and obtain project-specific ground and structural investigations before relying on a design or budget.

Plan temporary works, waterproofing, ventilation, escape and spoil removal as part of the same brief. Ask Hampstead Chartered Surveyors to assess party-wall matters and Hampstead Architecture & Planning to coordinate the design requirements. An area name alone does not establish ground conditions.

The local building context

The Stanmore Hill appraisal describes houses and some commercial units from the eighteenth to the early twentieth century on sloping land, among greenery and historic walls. Linear development reflects properties built mainly to serve travellers heading to London along Stanmore Hill, many of whom would have stopped at the Abercorn Arms, an eighteenth-century hotel. Stanmore Hill and upper Green Lane are relatively dense, with small terraced cottages on Green Lane, many fronting the pavement; further down Green Lane, medium-sized detached houses in spacious grounds dominate. Buildings usually do not exceed two storeys, and most are listed or locally listed.

Little Common, at 38 hectares the largest of the four in the 2013 SPD, gained cottages around the Common in the seventeenth century, then eighteenth- and nineteenth-century houses in large grounds, such as Stanmore Hall and Springbok House, which remain, subdivided or with their use changed. Tall walls mark historic estate boundaries, red and yellow brick and clay tiles are typical, and many original timber sashes and casements survive. Around Old Church Lane, the landowner Samuel Wallrock created an Old World, Tudor feel in the 1930s, using much older materials, and dark red handmade brick and clay tile predominate.

Kerry Avenue is different again. Its appraisal records an unusual concentration of inter-war and post-war houses in the Modern or International Style, laid out symmetrically on the axis of Stanmore Station, which opened on 10 December 1932 and became the terminus of the Metropolitan Line, and the 2013 SPD describes its well-preserved Modernist buildings as forming the earliest domestic group in west London. The houses are two or three storeys, with flat roofs often carrying sundecks and curved bays often holding the stair; all are brick, some designed with render to look like concrete against large Crittall windows.

Local design and consent context

Harrow’s Stanmore and Edgware page lists Little Common, Stanmore Hill, Old Church Lane and Kerry Avenue, each with an appraisal, a map and an Article 4 entry. Each appraisal and management strategy is dated December 2013 and forms an appendix to the Stanmore and Edgware Conservation Areas SPD. Harrow’s map documents record the first three as adopted at Cabinet on 12 December 2013, and Kerry Avenue’s as adopted that December.

Harrow explains that an Article 4 direction removes permitted development rights, and its table marks directions as applying in all four Stanmore conservation areas. Each direction applies to the properties or land its schedule names, and most, including all those of June 2023, apply only where the works would front a highway, a waterway or open space. In the Stanmore Hill conservation area, the first schedule of the January 2003 direction, which carries that limit, names properties on Green Lane and on Stanmore Hill, including Nos 75–81 (odd), and controls extensions and alterations, roof changes, porches, hard surfaces, satellite antennas, gates, fences and walls, and exterior painting.

Harrow counts over 300 listed building entries in the borough and 909 locally listed buildings, which are protected locally by planning policy rather than to the statutory standard. Stanmore Station is locally listed and part of the Kerry Avenue conservation area, and Harrow’s local list of parks and gardens includes Bernays Gardens, Stanmore Recreation Ground and Little Common, Stanmore. Ask Harrow whether a building or garden near the work is on the current lists.

Access and site planning

Under powers in the Control of Pollution Act 1974, Harrow permits noisy construction work from 8am to 6pm, Monday to Friday, and 8am to 1pm on Saturday, with none on Sundays or bank holidays, and suggests warning neighbours in advance about the work and how long it will last. In a flat, ask the managing agent about any building rules on working hours, deliveries and common parts, and if you stay at home, agree which rooms remain in use and when water or power will be off.

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The Stanmore area guide · Basement conversion across London · Hampstead Architecture & Planning · Hampstead Chartered Surveyors

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