House
extensions
in Barnes, SW13
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Hampstead Chartered Surveyors & Building ConsultancyA Barnes extension follows Richmond's house extensions guidance: a single storey usually acceptable to 3m on a terrace and 3.5m on a semi, and two storey additions at most half as wide as the original house.
Barnes keeps its village character within London, and an extension is designed to preserve it. The neighbourhood belongs to Richmond upon Thames, its conservation area guarding the setting around the pond and the river; the borough examines external change and enforces Article 4 controls. Church Road runs through the heart past the pond, period cottages and villas ring Barnes Green, and Glebe Road carries handsome Victorian and Edwardian family houses.
The river is the second defining factor. Castelnau brings grand Victorian villas toward the bridge, and riverside houses generally call for substantial refurbishment with attention to flood resilience. So near the Thames a rear addition is worked up with flood measures designed in from the outset, rather than bolted on, alongside the conservation-area character the village expects.
The build reflects both village and river. Rear access, party-wall awards, foundations beside older brickwork, drainage and boundary limits all shape the figure. A Barnes rear extension or side return is priced after a survey.
Depth, width and the spaces between villas
Richmond's House Extensions and External Alterations SPD gives the starting depths: the guidance usually accepts a single storey rear extension of 3m behind a terraced house, 3.5m behind a semi and 4m behind a detached house, though the circumstances of a particular site can justify more.
Infill extensions to Victorian houses are common across the borough, and where one runs deeper than those figures the guidance keeps its eaves to 2.2m so the neighbour does not feel hemmed in.
Upstairs the limits tighten. A two storey side or rear addition is kept to half the width of the original building at most, set 1m in from the side boundary, with eaves level with the house's own or below them.
On Castelnau that spacing has a history: the statement notes that stables of a subordinate scale link many of the villas, giving the road a pronounced rhythm in its building line.
The guidance expects an extension's external materials to match the house, normally as a condition of the permission, and suggests setting new brickwork back from the old face, because weathered brick rarely matches exactly.
A window that faces a neighbour is either set high, 1.7m up from the floor, given obscure glass, or not put in at all, and an extension's flat roof will normally be refused as a balcony.
Outside Barnes: Holland Avenue, Wimbledon, an SW20 house that we extended at the rear.
We draw the neighbours' rear windows and garden walls onto our survey before sketching an extension, since the depth and height that work on a Barnes plot depend on them.
Sources: Richmond upon Thames Council: House Extensions and External Alterations Supplementary Planning Document (May 2015); Richmond: House Extensions and External Alterations SPD (May 2015); Richmond: Castelnau conservation area statement (No. 25).
House Extensions in Barnes: Questions
On a Barnes semi, how far back can a single-storey extension reach?
Richmond's guidance treats 3.5m as usually acceptable on a semi-detached house, 3m on a terrace and 4m when detached, with the final test resting on the site itself: distances to boundaries, heights and the neighbours' layouts.
Can the flat roof of a Barnes extension be used as a terrace?
Normally not. Richmond's guidance treats a balcony on an extension roof as normally unacceptable, so a roof terrace would need a different design and a case of its own.
How does Barnes's village conservation area affect an extension?
Through Richmond's conservation-area policy, which asks every proposal to preserve and, where possible, enhance the area's character, and through any Article 4 direction, which takes away specified permitted development rights so the work needs an application.
Do I need to consider flooding when extending a Barnes house?
Near the Thames, check the zone first: the House Extensions guidance treats any extension in the functional floodplain, Zone 3b, as unacceptable, and the address's place on the flood maps sets what else is needed.
What does a house extension cost in Barnes?
Each one is priced once we have surveyed the house and the plot: the depth the guidance allows, the foundations the ground needs and how materials reach the garden all move the figure.
What construction issues come up on Barnes houses?
Matching the house. The guidance asks for a pitched roof on two storey additions, black rather than grey replacement rainwater pipes, and new work that carries on the plinths, string courses and fascias of the original.
What kind of houses will I be extending in Barnes?
Castelnau's villas, Lonsdale Road's houses of the 1860s, Edwardian terraces north of Church Road, the 1930s Henry Boot estate in north Barnes and the cottages of Thorne Passage, each with its own pattern at the back.
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