Estiquote

Local costs · South West · September 2026

How much does an extension cost in Bath and North East Somerset?

A mid-range 25 m² single-storey extension in Bath and North East Somerset costs about £65,500 to £81,000 including VAT, or £2,600 to £3,200 per m² at South West prices. Bath and North East Somerset charges £696 for building control on a 10 to 40 m² extension (full plans, including VAT): the 14th cheapest of the 91 councils we checked, 17% below the typical council (£840), though its published schedule is older or undated. With design, a structural engineer, building control and a 15% contingency, budget £81,000 to £105,000.

By Estiquote · Prices reviewed · Council fees from Bath and North East Somerset's published schedule · How we calculate

Work out your project in Bath and North East Somerset

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Typical prices in Bath and North East Somerset

Mid-range finish, South West prices, including VAT. The budget adds design and engineering fees, Bath and North East Somerset's building control charge and a 15% contingency.
ProjectBuilding workBudget to plan for
Single-storey extension, 25 m²£65,500 to £81,000£81,000 to £105,000
Double-storey extension, 40 m²£95,000 to £120,000£116,000 to £152,000
Dormer loft conversion, 30 m²£58,500 to £72,500£72,500 to £93,000
Kitchen, medium£9,200 to £16,300£10,600 to £18,800
Bathroom refit£6,100 to £9,200£7,100 to £10,600

Building prices in South West run about 4% above the UK average outside London. Kitchens and bathrooms vary less from place to place than extensions and lofts.

Building control fees in Bath and North East Somerset

Bath and North East Somerset council charges including VAT (plan and inspection combined)
WorkCharge
Extension up to 10 m² (full plans)£696
Extension 10 to 40 m² (full plans)£696
Larger extension, 40-60 m² (full plans)£876
Extension 10 to 40 m² (building notice)Not published
Loft conversion up to 40 m²£660
Garage conversion£408

Bath and North East Somerset charges £696 for building control on a 10 to 40 m² extension (full plans, including VAT): the 14th cheapest of the 91 councils we checked, 17% below the typical council (£840), though its published schedule is older or undated. Source: Bath and North East Somerset's building control charges, Not stated. Inc VAT total column.

Check before relying on it: the schedule is older than 2025 or undated, so check it is still current.

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 Bath and North East Somerset compares with every council we checked.

Notes on Bath and North East Somerset's schedule

Own page. Single charge. Building-notice equivalence not stated. Garage figure is up to 30 m2.

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 South West

Building control for a 10 to 40 m² extension:

Questions people ask

How much does an extension cost in Bath and North East Somerset?

A mid-range 25 m² single-storey extension in Bath and North East Somerset costs about £65,500 to £81,000 including VAT for the building work, or £2,600 to £3,200 per m², based on South West prices reviewed in September 2026. With fees and a 15% contingency, budget £81,000 to £105,000.

How much is building control in Bath and North East Somerset?

Bath and North East Somerset charges £696 (including VAT) for a 10 to 40 m² extension (full plans), according to its published schedule (Not stated).

How much does a loft conversion cost in Bath and North East Somerset?

A mid-range 30 m² dormer loft conversion in Bath and North East Somerset costs about £58,500 to £72,500 including VAT for the building work, and about £72,500 to £93,000 with fees and a 15% contingency.

Before you get quotes