Group C · External wall insulation and render
External wall insulation (EWI)
A complete certified build-up of insulation board, mesh and render from one system holder.
Price by property type
External wall insulation + render
- Mid-terrace£9,000–£15,000
- Semi / end-terrace£14,000–£24,000
- Detached£20,000–£35,000
- Bungalow£12,000–£20,000
- Flat / block£130–£220 per m²block
Before grants · updated 11 October 2026 · a survey confirms the final figure.
- Best for
- Solid-wall, non-traditional and hard-to-treat homes; transforming how a home looks
- Guarantee or standard
- System guarantee (up to 25 years with SWIGA or system holder)
- Time on site
- EWI on a typical house usually takes a few weeks including scaffolding, depending on size, detailing and weather.
- Typical price
- From £9,000
What it is
What is external wall insulation?
A complete certified build-up of insulation board, mesh and render from one system holder.
Best for: Solid-wall, non-traditional and hard-to-treat homes; transforming how a home looks.
Build-up
External wall insulation system
- 1Existing wall
- 2Adhesive and mechanical fixings
- 3Insulation boardEPS, mineral wool, phenolic, wood-fibre or cork
- 4Base coat with glass-fibre mesh
- 5Render or brick slip finish
Who it suits
Which homes is external wall insulation suitable for?
Is my home suitable?
Pick your property type for a straight answer on external wall insulation.
Guidance only — every home is different, and a survey confirms what suits yours.
Houses
- Detached house
- Semi-detached house
- End-of-terrace
- Mid-terrace
- Townhouse
- Mews house and cottage
- Detached bungalow
- Semi and terraced bungalow
- Chalet and dormer bungalow
- Period home
- 1930s home
- Post-war and ex-council house
- Non-traditional / system-built
- Farmhouse, barn conversion or rural home
- New build or self-build
- Park and mobile home
Flats and blocks of flats
Commercial and public buildings
Usually suitable Depends — a survey confirms
Not usually suitable for 3 property types
- Listed building or conservation area — Listed buildings need consent, and fronts in conservation areas need planning — breathable IWI or thermal lime render are the usual routes.
- Purpose-built flat — A single flat can't have EWI on its own: the outside walls belong to the building, and flats have no permitted development rights for EWI. It's done as a whole-building project.
- Mansion block — A single flat can't have EWI on its own: the outside walls belong to the building, and flats have no permitted development rights for EWI. It's done as a whole-building project.
Materials and brands
What we use
EPS, mineral wool, phenolic, wood-fibre or cork board, adhesive and mechanical fixings, polymer base coat with glass-fibre mesh, then a render or cladding finish — one certified system, never mixed components.
EWI and render brands we work with
- Sto
- Weber
- K Rend
- Wetherby
- Parex
Insurance-backed EWI usually requires approved-installer status with the system holder. The exact system and brand for your home are confirmed in your written quote.
Heat, bills and EPC
What it does for your heat loss, bills and EPC
Solid and system-built walls lose far more heat than insulated cavity walls. Wrapping them in insulation lowers the wall's U-value, keeps the masonry warm and dry, and reduces cold bridging at floors and junctions — for a solid-wall home, often the biggest single EPC improvement available. Render alone does not change the wall's U-value.
See the EPC points and savings for your home in the EPC plannerU-value before and after, typical heat and bill saving, and EPC points — worked out for your property.Price
How much does external wall insulation cost?
Prices change with your property type. Pick your column — the quote builder then refines it for your home.
| Measure | Mid-terrace | Semi / end-terrace | Detached | Bungalow | Flat / block |
|---|---|---|---|---|---|
| External wall insulation + render | £9,000–£15,000 | £14,000–£24,000 | £20,000–£35,000 | £12,000–£20,000 | £130–£220 per m²block |
Indicative ranges for London and the South East, supplied and installed, including VAT, before grants. Updated 11 October 2026. A survey confirms your final price.
0% VAT on energy-saving materials
Insulation, solar panels, batteries and heat pumps installed in homes in Great Britain are zero-rated for VAT until 31 March 2027. Windows and doors are not included.What to expect
Time on site, disruption and approvals
Time on site
EWI on a typical house usually takes a few weeks including scaffolding, depending on size, detailing and weather.
Disruption
Most of the work happens outside, so you stay in your home. Scaffolding is up for the duration, and downpipes, meters, lights and satellite dishes are moved and refitted.
Planning and building control
Houses often don't need planning permission when the finish is similar to the existing walls, but an application may be needed where the appearance changes, on fronts in conservation areas, or under an Article 4 direction. Flats have no permitted development rights for EWI. EWI is building work, and we handle building control.
Guarantee and standard
System guarantee (up to 25 years with SWIGA or system holder). The guarantee and certification for your job are confirmed in writing in your quote.
60-second grant check
Could a grant help pay for it?
Grant eligibility checker
About 60 seconds · plain results: likely, possibly or not eligible
Before we start
What type of property is it?
Questions
External wall insulation (EWI): your questions answered
How much does external wall insulation cost?
Typical installed prices in London and the South East, including VAT and before any grant: £9,000–£15,000 for a mid-terrace; £14,000–£24,000 for a semi-detached or end-of-terrace house; £20,000–£35,000 for a detached house; £12,000–£20,000 for a bungalow; £130–£220 per m² for a flat. Prices updated 11 October 2026. A survey confirms your final figure.
What is external wall insulation?
A complete certified system fixed to the outside of your walls: insulation boards, adhesive and mechanical fixings, a polymer base coat with glass-fibre mesh, then a render or cladding finish. It keeps the walls warm and gives the house a new face.
Is external wall insulation better than internal wall insulation?
For many solid-wall and system-built homes, yes: you lose no room space, cold bridges at floors and junctions are reduced, and you can stay in while we work. Internal insulation is the choice where the outside must not change.
Do I need planning permission for external wall insulation?
Often not on houses where the finish is similar to what's there, but an application may be needed where the look changes, on fronts in conservation areas, or under an Article 4 direction. Flats have no permitted development rights for EWI. We check at survey.
Which insulation board is best for EWI?
It depends on the wall and the building. EPS is the most common and cost-effective; mineral wool is non-combustible and required on taller buildings; phenolic is the thinnest; wood-fibre and cork are breathable for period homes.
What guarantee comes with external wall insulation?
System guarantees of up to 25 years are available through the system holder or SWIGA when the system is installed by an approved installer. The guarantee for your job is confirmed in writing in your quote.
Group C
More in external wall insulation and render
EWI with brick slip finish
External wall insulation finished in brick slips so it looks like real brick.
K Rend silicone through-coloured render
One- or two-coat silicone render that cleans itself and never needs painting.
Monocouche render
Through-coloured single-coat cement render.
Acrylic and silicone thin coat
Thin finishes over a base coat and mesh for a smooth modern finish.
Lime render
Breathable lime render and lime plaster for older solid walls.
Insulating (thermal) lime render
Lime render with an insulating aggregate for modest U-value gains on old walls.
Begin your project
Price external wall insulation in two minutes
See a price range for your property type, with grants and 0% VAT applied where they fit. A survey always confirms the final figure.