The short answer
External wall insulation in the UK typically costs around £90–£150 per square metre installed with a standard render finish, with some systems and locations sitting a little higher. By property that usually works out at roughly £8,000–£15,000 for a three-bed semi, less for a small terrace and more for a detached home, because you largely pay per square metre of wall. The main drivers are your wall area, the insulation thickness and render system, scaffolding and access, and any repairs to the existing wall before work starts. Grants can reduce these figures substantially where you qualify — see the grants page. As always, the accurate number comes from a measured survey, not a brochure.
Price depends mainly on how many square metres of external wall you have, the system specified, and access. The figures below are typical installed prices for guidance, not quotations.
Typical UK costs
- Installed, with render£90–£150 / m²
- Mid-terrace~£6,000–£10,000
- Three-bed semi~£8,000–£15,000
- Detached house~£12,000–£22,000
- Scaffolding (where needed)often included in the m² rate
What drives the price
- Wall area: you pay largely per square metre, so a detached home with more external wall costs more than a mid-terrace with two exposed sides.
- System & thickness: the insulation board type and thickness and the render system specified all move the rate.
- Access & scaffolding: a two-storey or awkward-access property needs more scaffolding and time.
- Wall preparation: repairs to existing render, damp issues, or moving pipes, vents and downpipes add to the figure.
| Item | Typical figure | Notes |
|---|---|---|
| Installed, with render | £90–£150 / m² | varies by system & access |
| Mid-terrace (full) | ~£6,000–£10,000 | fewer exposed walls |
| Three-bed semi (full) | ~£8,000–£15,000 | common UK case |
| Detached (full) | ~£12,000–£22,000 | more wall area |
Indicative UK figures for guidance. Sources: Checkatrade and MyBuilder cost guides.
Why a grant can change the picture
EWI is a qualifying measure under the main UK insulation grant schemes, so where you are eligible the upfront figure can drop sharply or be fully funded. That also shortens the payback period considerably. Eligibility depends on your benefits status, EPC rating and property, so it is worth checking the grants page before assuming you will pay the full figures above.
Want a measured EWI quote?
We'll match you with a PAS2035/TrustMark EWI installer who surveys your walls and quotes on a clear specification — system, thickness, render, scaffolding and any wall repairs all set out.
Frequently asked questions
How much does external wall insulation cost in the UK?
Typically around £90–£150 per square metre installed with a render finish, which works out at roughly £8,000–£15,000 for a three-bed semi. A small terrace is usually less and a detached home more, because you largely pay per square metre of wall.
Does external wall insulation include the render?
Usually yes — a standard EWI system is the insulation boards plus a render finish, and the typical per-square-metre figures include both. Premium finishes such as brick-effect or some textured renders can cost more.
Why is the cost range so wide?
Because properties differ. Your wall area, the system and thickness, access and scaffolding, and any repairs to the existing wall all move the figure. A measured survey gives the accurate number for your home, and a grant can reduce it where you qualify.
Sources & further reading
Figures on this page are typical UK ranges drawn from published sources and depend on your specific property. They are guidance, not a quotation.