Basement conversion in Herne Hill

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

On the west side, Lambeth’s Herne Hill Conservation Area, first designated in December 2007, covers commercial and residential buildings of around 1900 near the road’s junctions with Half Moon Lane and Milkwood Road, in red or yellow stock brick under tile or slate. The 2012 statement finds commercial premises on the ground floor of the vast majority, often with storage or homes above; the one exception is Herne Hill Mansions, a wholly residential mansion block with a mature front garden. It notes that building east of the railway tended to be later, with detached and semi-detached houses in bigger gardens.

Opposite, most of the adjoining properties on the Southwark side fall in the Stradella Road Conservation Area, designated on 26 September 2000, which covers Stradella and Winterbrook Roads and bordering properties on Burbage Road and Half Moon Lane. Its appraisal describes mostly single-family houses with a small number of flats: principally semi-detached, on two floors with attic rooms, in plain red brick laid in Flemish bond, originally roofed mainly in natural Welsh slate, with mostly double-hung timber sash windows. A pocket of post-war houses replaced war-damaged ones in Stradella Road.

Southwark’s Sunray Estate Conservation Area, designated on 20 January 2009, lies on Denmark Hill in North Dulwich and includes part of the road Herne Hill. Built between 1920 and 1922 as cottage housing, it is described by the council as a small garden suburb. Its appraisal sets rendered main streets against brick-faced enclaves of flats and attached houses, with larger detached and semi-detached houses on Red Post Hill, white-painted wooden casements with small panes, and privet hedges with wooden gates about one metre high.

Local design and consent context

Lambeth consulted on a draft Herne Hill Conservation Area Statement from 26 October to 23 November 2009 and agreed the final version on 26 March 2012; it is a material consideration on planning proposals. For windows it suggests internal secondary glazing where more insulation is needed, says double glazing should be avoided because it rarely matches the original detail, and advises against metal, unpainted hardwood or uPVC units. Brickwork should not be cleaned, rendered, painted or clad, and natural slate is preferred on roofs.

For a Southwark address, decisions rest on the Southwark Plan 2022 (adopted 23 February 2022, running to 2036) and the Householder Development SPD that cabinet adopted on 7 July 2025, which requires planning permission for any new basement or basement extension and warns that an Article 4 direction can tighten the rules on new windows and doors. The council’s 2013 Dulwich SPD says Herne Hill has a few small development opportunities that need to respect conservation area protection.

For a Lambeth address, the Lambeth Local Plan 2021 has been the adopted plan since 22 September 2021, with a replacement now in preparation. Lambeth’s Design Guide, an SPD since 8 August 2023, generally supports dormers on a back roof slope; on a front slope it resists any that are not a feature of the building type or group (Part 4). It also expects most basement schemes to need planning permission (Part 5).

Access and site planning

Check the council before booking anything for the street, since Southwark and Lambeth follow different rules. In Southwark, the skip company applies for the licence at least 7 days before delivery, a scaffolding or hoarding licence is applied for at least 15 working days ahead, and a parking bay suspension needs seven days’ notice. In Lambeth, only the skip company can obtain a skip licence, a highways licence covers scaffolding, hoarding, fencing, gantries and stored materials, and a standard suspension, including one for a skip, needs 10 or more working days’ notice.

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

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