Single Storey Extensions in Towcester | Building Control Handled

A single storey extension in Towcester typically costs £2,400–£3,200 per m² finished ready for decoration — roughly £29,000–£38,500 for a 12m² rear extension, with any kitchen fit-out priced separately. An extension in Towcester needs building regulations approval — West Northamptonshire Council’s 2026 fee schedule lists a 10–40m² extension at £720 as a building notice, or £191.75 plan charge plus £528.50 inspection on full plans (including VAT); up to 10m² is £564.75 as a building notice. It either fits within permitted development or needs householder planning permission, which costs £548 from April 2026 and is decided within eight weeks. On streets covered by Towcester’s conservation area Article 4 direction, extensions facing the road need planning permission; rear extensions are not covered by it.

Typical cost: £2,400–£3,200 per m²
Council: West Northamptonshire Council
Planning: Permitted development or £548; road-facing work on Article 4 streets needs permission
Building regulations: Needed
Ground: Clay in the centre, better on the slopes

Prices are our 2026 guide prices; your fixed price comes in writing after the free visit. Council fees checked October 2026.

Extensions in Towcester

Extensions on Towcester houses

Towcester is a Watling Street coaching town of ironstone, limestone and red brick built right up to the pavement, with yards behind, suburban streets where parking has taken over many front gardens, and the 2,750-home Towcester South extension to the south.

Most extensions we build here are single storey at the rear, matched to the existing brick or stone, with the drainage and any sewer nearby checked before the footings are dug.

We cover Towcester (NN12) and the areas around it, including Greens Norton, Paulerspury, Silverstone, Tiffield, Blisworth, Abthorpe, Shutlanger and Cold Higham. Travel does not change the price.

Towcester specifically

Ground, drainage and conservation in Towcester

The old town sits on a clay spur of Upper Lias between the Tove and Silverstone Brook, with limestone and Northampton Sand on the valley sides and boulder clay higher up. In the centre expect slow-draining clay; on the slopes drainage is better. Clay shrinks and swells, so foundations go deeper — deeper again near trees — and building control confirms the depth on site.

Towcester Conservation Area has a 1998 Article 4 direction on frontages to Watling Street, Moat Lane, Park Street and nearby streets. It removes permitted development for front extensions and alterations, roof changes, porches, gates, fences and walls, and painting. Front hard surfacing is not on the list.

The old core is surrounded on three sides by the Tove flood plain, and the Environment Agency runs a River Tove at Towcester flood warning area. You can check any address on the Environment Agency flood map.

Sources: Towcester Article 4 notice (London Gazette, 1998) · Environment Agency: River Tove at Towcester.

West Northamptonshire Council

Planning, building regulations and fees in Towcester

Step 1Check whether it fits permitted development, and if you want certainty apply for a lawful development certificate (£274). Planning Portal: extensions
Step 2On the streets covered by Towcester’s Article 4 direction, road-facing extensions need planning permission; rear extensions are not covered, but side and two-storey rear extensions in any conservation area always need permission. West Northamptonshire Council: Article 4 directions
Step 3If permission is needed, apply for householder planning permission (£548 from April 2026), decided within eight weeks. Pre-application advice from West Northamptonshire Council costs £135 for written advice, or £267 with a site visit. Planning Portal: application fees
Step 4Apply for building regulations approval: West Northamptonshire Council’s 2026 fee schedule lists a 10–40m² extension at £720 as a building notice, or £191.75 plan charge plus £528.50 inspection on full plans (including VAT); up to 10m² is £564.75 as a building notice. West Northamptonshire Council: building control fee schedule
Step 5We build to the approved drawings and work to the building control inspections at each stage.

Council fees and rules checked October 2026. Planning fees are the national fees from 1 April 2026.

What is included

Everything below is included in an extension

Drawings and the building control application
Foundations set from a trial hole, not a guess
Drainage diverted or rebuilt where it needs to be
Build-over and party wall matters flagged and handled
Roof and threshold junctions detailed properly
Electrics and plumbing by registered trades, with certificates
Building control sign-off at the end
A five year guarantee, in writing

Questions

Extensions in Towcester: questions

How much does a single storey extension cost in Towcester?

A single storey extension in Towcester typically costs £2,400–£3,200 per m² finished ready for decoration — roughly £29,000–£38,500 for a 12m² rear extension, with any kitchen fit-out priced separately. Your fixed price comes in writing after the free visit.

How much does planning and building control cost for an extension in Towcester?

Householder planning permission is £548 (from April 2026) if you need it, or £274 for a lawful development certificate. West Northamptonshire Council’s 2026 fee schedule lists a 10–40m² extension at £720 as a building notice, or £191.75 plan charge plus £528.50 inspection on full plans (including VAT); up to 10m² is £564.75 as a building notice.

Do I need planning permission for an extension in Towcester?

Many single-storey rear extensions are permitted development within size limits. On streets covered by Towcester’s conservation area Article 4 direction, extensions facing the road need planning permission; rear extensions are not covered by it.

Is Towcester in a conservation area?