Cavity Wall Insulation Cost UK 2026

Cavity wall insulation for a typical UK 3-bed semi costs £500–£900 in 2026. Blown bead or mineral fibre is pumped into the cavity through small holes drilled in the outer wall.

Quick answer

Typical UK price range: £500–£1,100. Typical time: 0.5–1 day.

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Insulation type Loft insulation (270mm) Cavity wall insulation External wall insulation Internal wall insulation Spray foam loft (open-cell)

Area to insulate (m²)

Region London South East South West Midlands North of England Scotland Wales Northern Ireland

Specification level Basic / standard Mid-range Premium / high-end

Extras

Pre-install survey £80–£200 Vapour control layer £150–£400 Ventilation upgrade £200–£600

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Estimate only. Prices reflect 2026 UK market data — get quotes from local tradespeople for accurate pricing.

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Budget Under £5,000 £5,000 – £15,000 £15,000 – £30,000 £30,000 – £60,000 £60,000+ Not sure

Timeline As soon as possible 1 – 3 months 3 – 6 months 6+ months Just researching

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Key points

• £500–£900 for a 3-bed semi
• £20–£35/m² of wall
• Saves £150–£300/year on heating
• Done in half a day, no internal disruption

Cost breakdown

Item	Low	High
Cavity insulation (3-bed semi)	£500	£900
Survey + boroscope inspection	£80	£200

Cost by UK region

Region	Typical cost
London	£1,080
South East	£1,000
South West	£880
Midlands	£800
North England	£720
Scotland	£760
Wales	£720

How to save money

• Always check for damp or wall ties first — survey costs £80–£200
• Use a CIGA-registered installer for the 25-year guarantee
• Don't insulate exposed coast/Pennine homes — risk of wind-driven damp

How to find a trusted tradesperson

Get at least 3 quotes from vetted UK trade networks:

• Checkatrade
• MyBuilder
• Bark

FAQs

Is cavity wall insulation safe?

Generally yes, but exposed locations (Pennines, coast) and certain wall constructions can suffer damp problems. Always survey first.

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Disclaimer: Prices are guide ranges based on 2026 UK market data. Get quotes from local tradespeople for accurate pricing.