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Costed
London cost guides

Building cost by London borough.

Independent UK cost expert cost guides for every major London borough, extensions, lofts, basements and full refurbs on 2026 rates. Each guide covers typical cost bands, local planning constraints and the questions homeowners actually ask before they commit.

Boroughs covered
SW1, SW3, SW5, SW7, SW10, W8, W10, W11, W14
Kensington & Chelsea
Extensions £3,800–£5,200/m² · Loft £95,000–£180,000
Cost guide
W1, W2, W9, NW1, NW8, SW1
Westminster
Extensions £3,600–£5,000/m² · Loft £90,000–£170,000
Cost guide
NW1, NW3, NW5, NW6, N1, N6, N7, N19, WC1, WC2
Camden
Extensions £3,200–£4,400/m² · Loft £75,000–£140,000
Cost guide
N1, N4, N5, N7, N19, EC1
Islington
Extensions £3,000–£4,200/m² · Loft £70,000–£135,000
Cost guide
E2, E5, E8, E9, N1, N16
Hackney
Extensions £2,800–£3,900/m² · Loft £65,000–£125,000
Cost guide
SW6, SW11, SW12, SW15, SW17, SW18, SW19
Wandsworth
Extensions £2,900–£4,000/m² · Loft £70,000–£135,000
Cost guide
TW1, TW2, TW9, TW10, TW11, KT2
Richmond upon Thames
Extensions £3,000–£4,200/m² · Loft £75,000–£145,000
Cost guide
SE1, SE5, SE11, SE21, SE24, SE27, SW2, SW4, SW8, SW9, SW16
Lambeth
Extensions £2,800–£3,900/m² · Loft £68,000–£130,000
Cost guide
SE1, SE5, SE15, SE16, SE17, SE22, SE26
Southwark
Extensions £2,800–£3,900/m² · Loft £65,000–£130,000
Cost guide
N4, N6, N8, N10, N15, N17, N22
Haringey
Extensions £2,700–£3,800/m² · Loft £62,000–£125,000
Cost guide
E1, E2, E3, E14
Tower Hamlets
Extensions £3,000–£4,100/m² · Loft £70,000–£135,000
Cost guide
W3, W5, W7, W13, UB1, UB2, UB5, UB6
Ealing
Extensions £2,600–£3,700/m² · Loft £60,000–£120,000
Cost guide
Last reviewed June 2026
London cost guides

What things actually cost in London.

Extension cost per m² in London

Working 2026 £/m² ranges for single and double-storey extensions across Greater London.

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Side return extension cost (London)

The Victorian-terrace side return, priced by m², with the spec choices that move the bill.

Read guide
Loft conversion cost UK 2026

Rooflight, dormer, hip-to-gable and mansard 2026 ranges, with London uplift.

Read guide
House extension cost UK 2026

Single, double, side-return, wrap-around and kitchen extensions, priced by type.

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Basement conversion cost UK 2026

Dig-down, underpinning and lightwell pricing with London party wall exposure.

Read guide
Kitchen extension cost UK 2026

Build cost + kitchen FF&E + the PC sum trap most builders use.

Read guide
Ready when you are

Know what your project should cost. Before you build it.

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