Estiquote

Local costs · London · September 2026

How much does an extension cost in Bromley?

A mid-range 25 m² single-storey extension in Bromley costs about £85,000 to £105,000 including VAT, or £3,400 to £4,200 per m² at London prices. Bromley charges £1,008 for building control on a 10 to 40 m² extension (full plans, including VAT): 20% above the typical council (£840). With design, a structural engineer, building control and a 15% contingency, budget £104,000 to £133,000.

By Estiquote · Prices reviewed · Council fees from Bromley's published schedule · How we calculate

Work out your project in Bromley

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Typical prices in Bromley

Mid-range finish, London prices, including VAT. The budget adds design and engineering fees, Bromley's building control charge and a 15% contingency.
ProjectBuilding workBudget to plan for
Single-storey extension, 25 m²£85,000 to £105,000£104,000 to £133,000
Double-storey extension, 40 m²£123,000 to £156,000£149,000 to £193,000
Dormer loft conversion, 30 m²£76,000 to £94,000£93,500 to £118,000
Kitchen, medium£10,600 to £18,800£12,200 to £21,500
Bathroom refit£7,300 to £10,900£8,300 to £12,500

Building prices in London run about 35% above the UK average outside London. Kitchens and bathrooms vary less from place to place than extensions and lofts.

Building control fees in Bromley

Bromley council charges including VAT (plan and inspection combined)
WorkCharge
Extension up to 10 m² (full plans)£720
Extension 10 to 40 m² (full plans)£1,008
Larger extension, 40-60 m² (full plans)£1,224
Extension 10 to 40 m² (building notice)£1,008
Loft conversion up to 40 m²£1,224
Garage conversion£648

Bromley charges £1,008 for building control on a 10 to 40 m² extension (full plans, including VAT): 20% above the typical council (£840). Source: Bromley's building control charges, 13 October 2025. Published ex VAT ("+VAT"); inc-VAT computed here at 20%.

Private approved inspectors set their own prices and are often competitive, so it is worth asking one or two for a quote as well. See how Bromley compares with every council we checked.

Notes on Bromley's schedule

Own schedule.

Planning

If your extension needs planning permission, a householder application in England costs £548. Many single-storey rear extensions are permitted development and need no application, and a lawful development certificate (£274) confirms it.

Other councils in London

Building control for a 10 to 40 m² extension:

Questions people ask

How much does an extension cost in Bromley?

A mid-range 25 m² single-storey extension in Bromley costs about £85,000 to £105,000 including VAT for the building work, or £3,400 to £4,200 per m², based on London prices reviewed in September 2026. With fees and a 15% contingency, budget £104,000 to £133,000.

How much is building control in Bromley?

Bromley charges £1,008 (including VAT) for a 10 to 40 m² extension (full plans), according to its published schedule (13 October 2025).

How much does a loft conversion cost in Bromley?

A mid-range 30 m² dormer loft conversion in Bromley costs about £76,000 to £94,000 including VAT for the building work, and about £93,500 to £118,000 with fees and a 15% contingency.

Before you get quotes