Heating · Updated 2026
Cavity wall insulation cost
Typical range£500–£3,500· Average cavity wall insulation (semi-detached)
Cavity wall insulation prices and grants available in 2025. In the UK, expect to pay between £500 and £3,500, with the typical project around £900 (average cavity wall insulation (semi-detached)). Regional variation, specification tier and site access conditions all shift the final quote.
Quick answer: Cavity wall insulation cost in the UK typically costs between £500 and £3,500 (Average cavity wall insulation (semi-detached)). London and the South East run 20–35% above this range; the North, Wales and most of Scotland sit 5–15% below.
Homeowners researching this typically also price up solid wall insulation cost and loft insulation cost. For wider context, browse our bathroom pricing, kitchen pricing and trades day rates.
Cost table
Indicative price ranges (UK, GBP)
| Item | Typical range (GBP) |
|---|---|
Mid-terraced house — Two exposed walls only | £500–£1,000 |
Semi-detached house — Three exposed walls | £800–£1,500 |
Detached house — All four walls | £1,200–£2,500 |
Bungalow — Larger footprint, one storey | £900–£1,800 |
Cavity wall extraction (removal) — Removing failed insulation | £1,500–£3,500 |
Labour costs
Labour typically accounts for 60% of the total project cost in the UK.
Labour line items
| Item | Typical range (GBP) |
|---|---|
CIGA-certified installer (per day) | £250–£400/day |
Scaffold / access (if needed) | £400–£1,000 |
Materials costs
Materials and fittings make up the remainder of the budget, with specification tier driving most of the variation.
Materials & fittings
| Item | Typical range (GBP) |
|---|---|
Mineral wool (injected) | £8–£15/m² |
EPS bead (injected) | £10–£18/m² |
Polyurethane foam (injected) | £15–£25/m² |
Factors affecting cost in the UK
- ·Region — London and the South East run 15–30% above national averages.
- ·Specification tier — premium materials and finishes can double the base cost.
- ·Access and site conditions — flats, restricted parking and listed buildings add time.
- ·Scope changes mid-project — late design decisions are the biggest cost overrun driver.
- ·Trade availability — quotes rise 10–20% in peak spring and summer months.
Ways to reduce cost
- ·Check ECO4 grant eligibility — many homes qualify for free install.
- ·Choose bonded bead over urea formaldehyde foam for better long-term performance.
- ·Combine with loft insulation through one CIGA-registered installer for a package discount.
- ·Avoid retrofit on exposed coastal or driving-rain zones unless surveyed first.
- ·Get the install done before re-pointing or repainting the external wall.
Frequently asked questions
- Is my house suitable for cavity wall insulation?
- Homes built from around 1920 onwards in England and Wales typically have cavity walls. A surveyor drills a small inspection hole to check. The cavity must be at least 50mm wide and unobstructed. Some areas with high driving rain exposure are not recommended.
- Are there grants available?
- Yes — the ECO4 scheme funds cavity wall insulation for eligible households. The Great British Insulation Scheme (GBIS) provides additional funding. Some energy suppliers offer free or subsidised insulation. Check eligibility via gov.uk or your energy supplier.
- Can cavity wall insulation cause damp?
- Poorly installed or inappropriate CWI can cause damp issues, particularly in exposed locations with heavy driving rain. Always use a CIGA-registered installer and check your property is suitable. Extraction and reinstallation is covered above.
- How much does cavity wall insulation save?
- The Energy Saving Trust estimates savings of £120–£250/year in a typical semi-detached home, depending on heating system and previous insulation levels.