Cavity insulation for new builds and extensions across Northamptonshire
We cover 7 towns in Northamptonshire, including Northampton, Corby, Kettering, Wellingborough, Rushden and more.
Before any material is chosen, exposure is checked. Much of Northamptonshire sits in the more sheltered driving-rain zones of the UK, which widens the choice of fill. Exposed elevations, coastal sites and high ground still get checked wall by wall.
A suitable wall in Northamptonshire is usually filled in a single day from outside, with drill holes made good to match the pointing. Where a Northamptonshire property has an extension or a conservatory, we check how the old and new walls meet, because that junction is often missed.
Building Regulations in England
Filling an existing cavity wall is notifiable building work in England. Either a building notice goes to building control before the work, or the installer self-certifies it through a government-approved competent person scheme such as CIGA's CWISC scheme. The insulation used must also be suitable for the wall it goes into, which is why the survey checks construction, condition and exposure first.
Funding in England
- ECO4, the energy-supplier scheme, has been extended to 31 December 2026 and government has said there will be no successor supplier obligation.
- The Great British Insulation Scheme closed as planned on 31 March 2026.
- Warm Homes: Local Grant supports low-income households in England through councils, and the January 2026 Warm Homes Plan sets out fully funded upgrades for low-income homes, with more detail still being published.
Sources: Planning Portal: cavity wall insulation and building regulations; CIGA: CWISC competent person scheme; GOV.UK: extending the ECO4 end date, government response; GOV.UK: Warm Homes Plan.
What we work from
Your architect's or designer's specification and the energy calculation for the job. We match the product, thickness and fixing to that spec, keep cavities clean as the walls rise, and fit cavity trays, closers and stop ends where shown so the building control inspection goes smoothly.
What is included
- Batts or boards to the specified U-value
- Clean-cavity working
- Trays, closers and stop ends as drawn
- Coordination with your bricklayers
- Photo record for building control
Cavity insulation for new builds and extensions prices in Northamptonshire
| Cavity insulation for new builds and extensions guide prices | Guide price |
|---|---|
| Full-fill batts supplied and fitted, per m² | £9–£16 |
| Partial-fill boards supplied and fitted, per m² | £14–£26 |
Prices are shown before any VAT; the VAT treatment for new-build work is confirmed on your quote. Guide ranges only: the fixed price is confirmed in writing before any work starts, and anything that could not be seen at survey is agreed with you first.
How it works in Northamptonshire:
Get in touch
Online, by phone or WhatsApp, whichever suits you.
Survey visit
The surveyor checks each wall and looks into the cavity where needed.
Your result in writing
What we found, what it means, and a fixed price if work is needed.
Booked work
Carried out by the installer named on your quote, with their scheme registrations.