Westminster, London
Boroughs · Central London
Westminster · Prime central

House extensions in Westminster

Prime-central Westminster demands heritage-grade detailing, Article 4 planning and premium logistics. Our KYB-verified builders specialise in listed and conservation work.

Typical all-in (inc VAT)
£140k–£210k
Cost vs London base
+18%
Postcodes covered
SW1 · W1 · WC2 · W2

Housing stock in Westminster

Grade-II stucco terraces, mansion blocks and mews houses — many in conservation areas.

Basement extensionsRear infillRoof / mansard

Planning in Westminster

Westminster City Council is one of the strictest in London. Article 4 removes many permitted development rights; expect a full householder application and heritage-officer consultation for anything visible from the street.

Party Wall Act — what to expect

Terraced and mansion-block context means a Party Wall Award is effectively guaranteed, often with two adjoining owners.

Read the Party Wall etc. Act 1996 guide for full detail on notices, timelines and surveyor costs.

Typical costs in Westminster

For a mid-spec 25 m² kitchen extension, all-in (professional fees, planning, party wall, VAT and 12% contingency), expect roughly £140,000 to £210,000. High-spec finishes, structural glazing or a full basement dig-out will push above the top of this range; a smaller side-return can come in under the bottom.

Cost tier
Prime central · +18% vs London average

Our calculator applies a 1.18× multiplier automatically for Westminster projects. Get an itemised breakdown in 60 seconds.

Get your Westminster estimate

Areas we cover in Westminster

SW1W1WC2W2

Why homeowners in Westminster pick us

  • KYB-verified builders only
  • Local Westminster project experience
  • Fixed, itemised written quotes
  • Full insurance & warranty checks
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