Cavity insulation for new builds and extensions for Harpenden properties
If your property is in Harpenden or the AL5 district or nearby St Albans, Hemel Hempstead and Welwyn Garden City, it is within our Hertfordshire coverage. It is about 5 miles north of St Albans.
If a wall in Harpenden is not suitable, for example because of an undiagnosed damp patch or a very exposed gable, you are told so in writing with the reason. For semi-detached and terraced homes in Harpenden, cavity barriers are fitted where your wall meets your neighbour's so the fill stays on your side.
Every elevation is judged on its own exposure. Much of Hertfordshire 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.
On compliance, in Harpenden filling a cavity is notifiable building work and needs a building notice or competent-person self-certification.
Funding in England
In England, ECO4 runs to 31 December 2026 and Warm Homes: Local Grant supports low-income households through councils.
Sources: 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 in Harpenden
- Photo record for building control
- Batts or boards to the specified U-value
- Coordination with your bricklayers
- Trays, closers and stop ends as drawn
Guide prices for Harpenden
| 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.
From enquiry to finish in Harpenden:
Tell us about the property
Postcode, property type and what you need.
Free survey
Walls, cavity, condition and exposure checked and photographed.
Written result and price
Suitable, suitable after repairs, or not suitable, with a fixed price.
Work and paperwork
Installation, making good, and the regulations and guarantee paperwork.