Estiquote

Local costs · South East · September 2026

How much does an extension cost in Horsham?

A mid-range 25 m² single-storey extension in Horsham costs about £72,500 to £89,500 including VAT, or £2,900 to £3,600 per m² at South East prices. Horsham charges £858 for building control on a 10 to 40 m² extension (full plans, including VAT): about the same as the typical council (£840). With design, a structural engineer, building control and a 15% contingency, budget £89,500 to £115,000.

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

Work out your project in Horsham

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Typical prices in Horsham

Mid-range finish, South East prices, including VAT. The budget adds design and engineering fees, Horsham's building control charge and a 15% contingency.
ProjectBuilding workBudget to plan for
Single-storey extension, 25 m²£72,500 to £89,500£89,500 to £115,000
Double-storey extension, 40 m²£105,000 to £132,000£128,000 to £166,000
Dormer loft conversion, 30 m²£65,000 to £80,000£80,000 to £102,000
Kitchen, medium£9,700 to £17,200£11,100 to £19,800
Bathroom refit£6,500 to £9,800£7,500 to £11,300

Building prices in South East run about 15% above the UK average outside London. Kitchens and bathrooms vary less from place to place than extensions and lofts.

Building control fees in Horsham

Horsham council charges including VAT (plan and inspection combined)
WorkCharge
Extension up to 10 m² (full plans)£858
Extension 10 to 40 m² (full plans)£858
Larger extension, <=60 m² (single band) (full plans)£858
Extension 10 to 40 m² (building notice)£858
Loft conversion up to 40 m²£858
Garage conversion£630

Horsham charges £858 for building control on a 10 to 40 m² extension (full plans, including VAT): about the same as the typical council (£840). Source: Horsham's building control charges, April 2026 (Sussex Building Control Fees April 2026). Published ex VAT ("please add 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 Horsham compares with every council we checked.

Notes on Horsham's schedule

Shared schedule: Sussex Building Control (Horsham and Crawley). Single band up to 60 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 East

Building control for a 10 to 40 m² extension:

Questions people ask

How much does an extension cost in Horsham?

A mid-range 25 m² single-storey extension in Horsham costs about £72,500 to £89,500 including VAT for the building work, or £2,900 to £3,600 per m², based on South East prices reviewed in September 2026. With fees and a 15% contingency, budget £89,500 to £115,000.

How much is building control in Horsham?

Horsham charges £858 (including VAT) for a 10 to 40 m² extension (full plans), according to its published schedule (April 2026 (Sussex Building Control Fees April 2026)).

How much does a loft conversion cost in Horsham?

A mid-range 30 m² dormer loft conversion in Horsham costs about £65,000 to £80,000 including VAT for the building work, and about £80,000 to £102,000 with fees and a 15% contingency.

Before you get quotes