How much does cavity wall insulation cost in the UK?
A cavity wall insulation costs £400 to £3,500 in the UK, typically around £1,200 for the house. Prices reviewed June 2026.
Cavity wall insulation is priced mainly by the size of the property. It is injected into the gap between the outer and inner walls, so the wall area and number of external walls drive the cost.
Price your cavity wall insulation
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Cavity wall insulation cost breakdown
What a cavity wall insulation typically costs, by option:
| Property size | Typical UK cost |
|---|---|
| Flat or small house | £400 to £900 |
| 3-bed semi | £900 to £1,800 |
| Large or detached | £1,800 to £3,500 |
What's included in the price?
A typical cavity wall insulation price includes:
- Survey to confirm the cavities are suitable
- Drilling and injecting the insulation
- Making good the drill holes
- A guarantee, often the 25-year CIGA cover
What changes the price?
The things that move a cavity wall insulation price most:
Property size and number of external walls
Wall construction and the condition of the cavity
Access and scaffolding for taller walls
Whether a grant covers part or all of the cost
Does where you live change the cost?
Fairly consistent nationally. Eligibility for ECO4 or the Great British Insulation Scheme affects the price more than where you live.
Common questions
A typical three bedroom semi costs roughly £900 to £1,800, before any grant. A flat is less and a large detached house more, because the price tracks the wall area.
For a suitable home with clear cavities it usually pays back through lower heating bills. On very exposed or damp-prone walls it is worth a survey first, as it is not right for every property.
These are independent guide prices based on typical UK jobs in 2026. Your actual cost depends on your property, spec, access and where you live. Always get at least three written quotes before committing.