Basement conversion in High Barnet and Monken Hadley

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

Barnet’s Monken Hadley Conservation Area Character Appraisal Statement, adopted in January 2007, describes an area that is still green, leafy and of low built density, with large Georgian houses and gardens around Hadley Green and the edges of the Common. Small Victorian cottages of stock brick or stucco line the road at Hadley Highstone, Hadley Green Road has a string of mainly Georgian listed buildings and Dury Road a range of listed buildings, several timber-framed. Hadley Grove has a group of Edwardian houses, and the High Street end is tighter, commercial and mostly Victorian.

Barnet’s Wood Street appraisal of July 2007 describes a conservation area running west along the ridge from St John the Baptist church at the top of Barnet Hill, taking in historic shops, Union Street, the villas facing Ravenscroft Park and Wood Street as far as The Whalebones. It records Victorian villas and terraces, almshouses, 18th and 19th-century houses and timber-framed buildings refronted in brick or stucco, with large central chimneystacks and clay-tiled roofs, such as 32 and 17 Wood Street. The land drops south of Wood Street towards the Dollis Brook, on ground the appraisal describes as largely London clay.

Homes change street by street. Ravenscroft Park has large late Victorian villas in small terraces of three or semi-detached pairs, mostly single-family homes in 2007; Union Street has modest buildings close to the road; and further west, Wood Street’s north side has substantial detached houses of about 1900 behind deep frontages. In 2007 the appraisals recorded flats over High Street shops, town-centre homes in Tapster Street, Moxon Street and Victors Way, mostly in modern purpose-built flats, conversions to flats such as the former Old Rectory on Wood Street, and Hadley Heights, a modern block of flats on the Common.

Local design and consent context

Monken Hadley (CA01) was designated in December 1968, one of Barnet’s first four conservation areas, and extended in February 1979 to the northern end of Chipping Barnet High Street. Barnet’s map, dated November 2023, gives its last amendment as 15 January 2007 and marks the borough boundary. The Character Appraisal Statement, adopted in January 2007 with a management plan, divides the area into ten sub-areas, from Hadley Highstone and Hadley Green to Barnet High Street, Camlet Way and Monken Hadley Common. Its guidance says extensions should normally be subordinate to the main building and need thoughtful design at the rear as well as the front, and that materials should match the existing building unless a contrast is intended.

Planning Data gives Wood Street (CA03) a designation date of 25 April 1969; the appraisal says it was extended in 1979, and Barnet’s Article 4 note records that after a council sub-committee on 7 June 2007 it took in 87 to 97 (odd) High Street, although Barnet’s November 2023 map still gives a last amendment of 1 October 1969. Its appraisal, adopted in July 2007, sets out five character areas, gives unlisted ‘positive’ buildings a general presumption in favour of retention and was to be reviewed every five years. Barnet’s open data lists no later appraisal for either area.

An Article 4(2) direction, A4D9, approved by Barnet’s Cabinet on 15 January 2007, is mapped as 15 areas. Where the work fronts a highway, waterway or open space, planning permission is needed for alterations including windows, doors and facing materials, roof-slope changes, porches, outbuildings and pools, hard surfaces, satellite antennas, gates, fences and walls and their demolition, and exterior painting; erecting, altering or removing a chimney is listed without that frontage condition.

Access and site planning

For a Barnet address, the council’s published construction working hours say noisy work should only be carried out Monday to Friday, 8am to 6pm, and Saturday, 8am to 1pm, and at no time on a Sunday or bank holiday. A lease or building manager may set tighter limits on noise, deliveries and shared parts. If you will live at home through the work, decide which rooms stay usable and when water or power will be off, and tell neighbours what is planned and when.

Continue planning

The High Barnet and Monken Hadley area guide · Basement conversion across London · Hampstead Architecture & Planning · Hampstead Chartered Surveyors

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