House
extensions
in Wandsworth Town, SW18
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Hampstead Chartered Surveyors & Building ConsultancyIn Old York Road extensions are suitable only at the rear, and in Wandsworth Town upward additions must step back from the house. An extension here is drawn against the terrace behind it.
Pricing follows the ground as much as the design. Foundations and drainage behave differently on a slope, rear access varies house by house, trees and boundary conditions shape what can be built, and materials have to come through dense SW18 streets — all of it surveyed and costed before a contract is signed.
Outriggers, rear mansards and the half-depth rule
Old York Road's appraisal is explicit: residential extensions are suitable only to the rear, outriggers should be limited to half the depth of the existing rear aspect, and squaring off the old outriggers should be avoided in favour of angled walls that keep the original plan legible.
It explains why. The land rises away from the station, many rear elevations can be seen from the street, and the rear mansards and outriggers added to enlarge the small houses have often raised the ridge and broken the stepping of the roofs.
In the Wandsworth Town conservation area, the appraisal asks that upward extensions always step back from the host building so they read as a later addition, and stay in scale with it, often a single storey given the two- to three-storey townscape.
North of East Hill the deep rear gardens give longer views through the residential area, which is why the appraisal values them; LP5 likewise wants a substantial depth of the original garden kept free of building.
The appraisal says smooth render has harmed the coherence of the terraces where it has been applied, and Wandsworth's Housing SPD asks for an extension's materials to match the main house.
Outside Wandsworth Town: Holland Avenue, Wimbledon, an SW20 family house extended at the rear and the side.
Boundaries are part of the scheme: Old York Road's appraisal asks that replacement boundaries copy the low brick walls or brick and rail of the same terrace, and Wandsworth Town's notes that painted or rendered boundary walls jar with the houses.
Rear gardens matter to the street too. The appraisal says glimpsed views to rear gardens and mature planting break up the backs of the terraces, which is one reason it limits outriggers.
We also check whether the house is one of the blocks of flats the Old York Road appraisal names, since those have no permitted development rights and every extension there needs a full planning application.
We measure the depth of the existing outrigger and of the neighbours' rear projections first, since Old York Road's half-depth rule is set against them.
Sources: Wandsworth: Old York Road conservation area appraisal (adopted 31 August 2023); Wandsworth: Wandsworth Town conservation area appraisal (adopted 31 August 2023); Wandsworth Local Plan 2023–2038 (adopted 19 July 2023); Wandsworth Council: Housing Supplementary Planning Document (adopted November 2016).
House Extensions in Wandsworth Town: Questions
Can solar panels go on an extension roof?
Yes, ideally where they cannot be seen from the street. The Wandsworth Town appraisal finds rear or side elevations the best place for them, and flush panels that look like slates may be considered case by case.
Can an extension in Wandsworth Town be rendered or painted?
Not usually in these conservation areas. Old York Road's appraisal says new external finishes need planning permission in its Article 4 area and will not normally be approved at the front, and Wandsworth Town's says smooth render has harmed its terraces.
How deep can an outrigger extension go on Old York Road?
The appraisal limits outrigger extensions to half the depth of the existing rear aspect, asks for angled rather than squared-off walls, and wants the result to read as subservient to the house.
Is Wandsworth Town covered by a conservation area?
Two cover much of it: Wandsworth Town, designated in 1984 and extended in 1989, and Old York Road, designated in 2019. Both appraisals were adopted on 31 August 2023 and guide extensions.
What extension work is typical in Wandsworth Town?
On Old York Road's two-storey terraces, rear outriggers and rear mansards are the usual ways owners have enlarged the smaller homes, which is why the appraisal now limits their size.
What should I plan for structurally when extending in Wandsworth Town?
The party walls first: GOV.UK says you must tell your neighbour before building on the boundary or digging near their foundations. Then the opening into the house, the foundations and the drainage.
Can I extend in Wandsworth Town under permitted development?
A house may, unless a direction removes the right, but blocks of flats have no permitted development rights in either conservation area, so their extensions always need planning permission.
What does a rear extension cost in Wandsworth Town?
Each extension is priced after a survey and a drawn scheme, from the area added, the structure and foundations, the roof and glazing and the finishes, before VAT.
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