Basement conversion in Barnsbury

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

Islington’s Barnsbury Conservation Area Design Guidelines, dated January 2002, call it the largest conservation area in Islington, declared to be of outstanding importance. They describe formal late-Georgian and early-Victorian residential developments, naming sequences of squares and terraces such as Lonsdale Square, Gibson Square and Thornhill Square, with mature trees and planting in many of the squares. They describe the area as predominantly residential, with shopping frontages on Liverpool Road and Caledonian Road, and say the council wishes to retain all listed and locally listed buildings and all other 18th and 19th century buildings there.

Islington’s Urban Design Guide names Barnsbury among the Georgian-era developments of squares, terraces and semi-detached villas built for the middle classes, completed by the mid-19th century as early Victorian building continued the Georgian style. The Islington Local History Centre’s Barnsbury trail dates Cloudesley Square, the earliest Barnsbury square, to 1826 and the first Thornhill Estate houses, 76–86 Richmond Avenue, to 1829. Lonsdale Square was designed in 1835 by Richard Cromwell Carpenter, College Cross and Barnsbury Square were developed in the 1830s, and Thornhill Square was begun in the 1840s.

The guidelines record buildings of brick, stucco and stone, with timber windows and doors and slate or tile roofs, and say the most common roof is the hidden valley roof behind a parapet. Some properties have front basement areas behind cast-iron railings, and gaps between detached and semi-detached villas give Barnsbury Square, Belitha Villas, Hemingford Road and Richmond Avenue a spacious character. Islington’s April 2010 local list describes 7, 8, 10 and 11 Barnsbury Square as villas of two storeys and basement with hipped slate roofs, and 16 Thornhill Road as three storeys plus basement in stock brick.

Local design and consent context

Islington’s table gives the Barnsbury Conservation Area (CA10) a designation date of 1 April 1969, a last amendment or extension on 22 April 2004 and current design guidelines adopted in January 2002. The guidelines say the council will operate special policies there to preserve and enhance the area’s special character and appearance. As the boundary was last changed after the guidelines were written, check the address on Islington’s current map. Regent’s Canal West (CA17), which the Site Allocations also list as adjacent to the Barnsbury Estate, was designated on 27 January 1981 and has its own guidelines of January 2002.

For a refurbishment, the guidelines bear most on the outside. Traditional roof extensions may be permitted on the properties listed in Schedule 10.2; otherwise none visible from any street level position will be permitted, including long views. New or enlarged dormers and rooflights are not permitted on the front or side slopes of exposed pitched roofs; plant rooms, air conditioning units and water tanks at roof level are opposed where they can be seen from the street or public space; and full width rear extensions above one storey are not normally permitted. The council seeks to keep porticos and traditional ironwork, and will not give permission to alter or remove original or traditional front walls and railings.

The Basement Development SPD, adopted in January 2016, notes that householder permitted development rights do not apply to flats or maisonettes and do not remove the need for listed building consent. In conservation areas it generally resists infilling front lightwells, says any front lightwell should go no lower than the original lower ground floor where one exists, and asks that basements under gardens leave the prevailing garden level unchanged. Islington says a basement usually needs planning permission.

Access and site planning

Islington allows noisy construction work only from 8am to 6pm Monday to Friday and from 8am to 1pm on Saturdays; outside those hours it needs the council’s prior approval. A lease or building manager may set tighter limits. If you stay at home, plan which rooms stay usable, when water and power go off and how neighbours and any managing agent will be told.

Continue planning

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

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