Estiquote

Local costs · East of England · September 2026

How much does an extension cost in Watford?

A mid-range 25 m² single-storey extension in Watford costs about £67,500 to £83,500 including VAT, or £2,700 to £3,300 per m² at East of England prices. Watford charges £1,065 for building control on a 10 to 40 m² extension (full plans, including VAT): the 15th dearest of the 91 councils we checked, 27% above the typical council (£840). With design, a structural engineer, building control and a 15% contingency, budget £83,500 to £108,000.

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

Work out your project in Watford

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Typical prices in Watford

Mid-range finish, East of England prices, including VAT. The budget adds design and engineering fees, Watford's building control charge and a 15% contingency.
ProjectBuilding workBudget to plan for
Single-storey extension, 25 m²£67,500 to £83,500£83,500 to £108,000
Double-storey extension, 40 m²£97,500 to £123,000£120,000 to £156,000
Dormer loft conversion, 30 m²£60,500 to £74,500£74,500 to £95,500
Kitchen, medium£9,300 to £16,600£10,700 to £19,000
Bathroom refit£6,300 to £9,400£7,200 to £10,800

Building prices in East of England run about 7% above the UK average outside London. Kitchens and bathrooms vary less from place to place than extensions and lofts.

Building control fees in Watford

Watford council charges including VAT (plan and inspection combined)
WorkCharge
Extension up to 10 m² (full plans)£760
Extension 10 to 40 m² (full plans)£1,065
Larger extension, 40-100 m² (full plans)£1,367
Extension 10 to 40 m² (building notice)£1,086
Loft conversion up to 40 m²£752
Garage conversion£696

Watford charges £1,065 for building control on a 10 to 40 m² extension (full plans, including VAT): the 15th dearest of the 91 councils we checked, 27% above the typical council (£840). Source: Watford's building control charges, 28 January 2026. Inc VAT ("Charge includes VAT 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 Watford compares with every council we checked.

Notes on Watford's schedule

Shared schedule: Watford BC / St Albans DC building control (WBC-SADC).

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 East of England

Building control for a 10 to 40 m² extension:

Questions people ask

How much does an extension cost in Watford?

A mid-range 25 m² single-storey extension in Watford costs about £67,500 to £83,500 including VAT for the building work, or £2,700 to £3,300 per m², based on East of England prices reviewed in September 2026. With fees and a 15% contingency, budget £83,500 to £108,000.

How much is building control in Watford?

Watford charges £1,065 (including VAT) for a 10 to 40 m² extension (full plans), according to its published schedule (28 January 2026).

How much does a loft conversion cost in Watford?

A mid-range 30 m² dormer loft conversion in Watford costs about £60,500 to £74,500 including VAT for the building work, and about £74,500 to £95,500 with fees and a 15% contingency.

Before you get quotes