Kitchen with a marble topped island and glass pendant lights.

Extensions in Westminster.

Central London · SW1 · Central London apartment, interiors and joineryCompleted work, photograph

Westminster by the river is almost all apartments. An extension here is usually lateral, into the flat next door.

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More space, on the same floor.

Lateral
The usual way to add space here
76%
Of the city sits in conservation areas
SW1P · SW1H
Georgian terraces and mansion blocks

NU Projects is a design and build company in Fulham SW6, founded in 2010. We handle house and kitchen extensions in Westminster SW1P, under one contract. A rear kitchen extension typically runs £160k to £250k. A side return extension typically runs £140k to £220k. Call 020 7731 6841, and a budget estimate typically follows within seven days.

Near the river, Westminster is Georgian terraces and mansion blocks. Almost every home is an apartment, many leasehold.

There are few gardens to build into. So the honest route to more space is lateral.

Two flats side by side on one floor become one. The wall between them is opened, under notice.

The freeholder must agree, and leases often set the terms. Listed buildings add a second consent.

Roof storeys are rare. Roofs in long views from public spaces are not normally extended.

What the council allows in Westminster.

Council
City of Westminster, for planning and listed building consent alike.
Conservation areas
Westminster has 56, covering about 76% of the city.
Listed buildings
Over 11,000 in the city. Work affecting character needs listed consent.
Long views
Roofs exposed to long views from public spaces are not normally extended.
Party walls
Opening a party wall is party structure work. Notice goes two months ahead.
Flood risk
Flood zones 2 and 3 need a site specific flood risk assessment.

Source: Westminster’s conservation areas and listed buildings guidance. Read on 25 October 2026. Policies change, so we read them again for your address.

Apartments we have built in SW1.

Oak larder cupboard opened to show shelves and drawers.

Central London·Apartment

Central London apartment, interiors and joinery

An SW1 apartment we designed and fitted out, close by.

See the project
Entrance lobby with blue velvet chairs and a bronze door.

Belgravia·Apartment

Belgravia apartment, full refurbishment

A Belgravia apartment we refurbished, a little way west.

See the project

Completed work, photographs

What a house extension costs in Westminster.

Joining two flats brings legal, licence and party wall costs.

We price the build open book, once the leases are clear.

Open the calculatorThe 2026 cost guideCan I build it here?

Can I combine two flats in Westminster into one lateral home?

Sometimes, where both leases and the freeholder allow it.

The opening between them needs party wall notice.

Planning is checked before any design.

Can I add a floor to a Westminster mansion block flat?

Rarely as a flat owner. Roof space usually belongs to the freeholder.

Roofs in long public views are not normally extended.

Flats have no permitted development rights.

Does listed consent apply inside a Westminster apartment?

If the building is listed, yes. Listing covers the whole building.

Works affecting its character need consent, inside or out.

Does flood risk affect building work in Westminster near the river?

It can. Flood zones 2 and 3 need a site specific assessment.

We check the zone early, before design.

Tell us about your home in Westminster.

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