House
extensions
in Westminster, SW1
Architects, Engineers, Surveyors & Builders Under One Roof.
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Hampstead Chartered Surveyors & Building ConsultancyLord North Street keeps a crisp building edge and a consistent height to width ratio, the Smith Square audit says, so an addition to one of its listed houses stays at the back and below the line of the terrace.
The residential heart of Westminster is its Georgian enclave, and it is some of the most tightly protected ground in the country. The streets around Smith Square and the Division Bell district fall within the Westminster Abbey and Parliament conservation areas; external change is exceptionally tightly controlled, listed-building consent applies widely, and security and access near Parliament add their own constraints. An addition here begins as a heritage and consent exercise rather than a building one.
The stock is exceptional and heavily listed. Smith Square and Lord North Street rank among the most intact Georgian streets in London, restored with authentic brick and joinery; Barton Street and Cowley Street carry fine small townhouses where listed-building consent governs interiors as well as facades; and Great Peter Street and Vincent Square add larger houses and mansion flats. So even internal reconfiguration is designed for consent at each step.
Cost is led by that control and by the logistics near Parliament. A Westminster rear extension or side return is priced after a survey, with heritage consent driving the balance.
Extending a listed Westminster town house
The Smith Square audit describes the houses on the north side of Smith Square, Lord North Street, Cowley Street and Barton Street as brown brick terraces of three storeys, with mansards and basements, built about 1722 to 1726 and all listed at Grade II*. We expect an extension to one of them to need both planning permission and listed building consent, confirm that with Westminster at the start, and design from what survives at the back.
The audit says the area as a whole keeps a sense of unity and architectural coherence. An addition is therefore kept low, behind the line of the main house, and built in brown brick in Flemish bond to match the eighteenth century fronts the audit describes.
A different brick may be right for a different street: the audit notes that a group of houses in Gayfere Street is in yellow stock brick, so we match the house in question, not the street average.
These are intimate routes, in the audit's words, and access for deliveries is tight. Saturday digging and piling need special permission from Westminster, so foundation work is sequenced for weekdays.
We commission a heritage statement early, prepared alongside the measured survey, so that the design responds to what the listing protects rather than being adjusted after a consent officer has seen it.
One related project, though not in Westminster, is Fitzjohns Avenue, NW3, the construction of a basement and a rear extension at an NW3 house. We point to it because the work is comparable; the project itself is outside Westminster.
Rear yards here are small, and we test early how much daylight a new addition would take from the neighbours' basement and ground floor windows, adjusting its height before the drawings go to Westminster. Brick samples are matched on site against the original rear wall, in daylight, before any are ordered, and the mortar mix is agreed with the conservation officer. Drainage from the new addition is connected to the existing system at the rear, and its route is drawn on the plans so the neighbours can see it.
Sources: Westminster City Council: Smith Square conservation area audit (SPG, adopted 14 January 2005); Westminster City Council: noise problems we can investigate.
House Extensions in Westminster: Questions
Why is extending near Smith Square and Westminster among the hardest in London?
Because it is some of the most tightly protected ground in the country. The streets around Smith Square and the Division Bell district fall within the Westminster Abbey and Parliament conservation areas; external change is exceptionally tightly controlled, listed-building consent applies widely, and security and access near Parliament add their own constraints.
How much of this part of Westminster is listed?
A great deal. Smith Square and Lord North Street rank among the most intact Georgian streets in London, restored with authentic brick and joinery, and on streets such as Barton Street and Cowley Street listed-building consent governs interiors as well as facades. So an addition or internal alteration is designed for the heritage case throughout.
What does an extension or reconfiguration cost in Westminster?
A Westminster rear extension, side return or wraparound is priced after a survey, as each depends on its scope. Given the near-total listed control and security-driven access near Parliament, the consent strategy usually leads a scheme's figure.
Does access near Parliament really affect building work?
Yes. Security and access near Parliament add real constraints, so deliveries, storage and site set-up in the Georgian enclave are planned carefully. Leading with the consent strategy keeps a Westminster scheme on track, and the logistics around the Division Bell district are built into the programme.
What is the property stock like in this part of Westminster?
The residential heart of Westminster is its Georgian enclave: Georgian townhouses, listed Westminster terraces and mansion flats. Smith Square and Lord North Street rank among London's most intact Georgian streets, Barton Street and Cowley Street carry fine small townhouses beloved of the political world, and Great Peter Street and Vincent Square add larger houses and mansion flats.
