Insulation · Group C
External wall insulation and render — insulation, render and windows in one contract.
Insulation, render and new windows in one contract — certified systems including K Rend and brick slip.
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
Overview
About external wall insulation and render
External wall insulation wraps your walls in a complete, certified system — insulation board, fixings, base coat and mesh, then a render or brick slip finish — and transforms how a home looks. Paired with new windows from LINX Glass, it's one contract, one scaffold and one team.
Every system is installed as a full build-up from one system holder, never mixed components. And render without insulation is a separate service: it renews a wall's finish, but we never sell it as insulation.
Every service in group C
9 ways we can help
External wall insulation (EWI)
A complete certified build-up of insulation board, mesh and render from one system holder.
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.
Sand and cement, pebbledash and spar dash
Traditional renders, repairs and re-dashing.
Render repairs, removal and painting
Hacking off failed render, crack repair, mesh reinforcement, masonry paint and render cleaning.
One certified system
What goes into an EWI system
| System part | Options | Why it matters |
|---|---|---|
| Insulation board | EPS (white or graphite-enhanced), mineral wool (non-combustible, required on taller buildings), phenolic (thinnest), wood-fibre (breathable, period homes), cork | Decides the thickness, fire performance, breathability and price — see the comparison below. |
| Fixing | Adhesive plus mechanical fixings; rail systems for uneven walls | The fixing pattern depends on the wall type and the wind load where the house stands. |
| Base coat and mesh | Polymer-modified base coat with glass-fibre mesh, corner beads, stop beads | The glass-fibre mesh spreads movement across the wall, which is what stops the render cracking. |
| Render finishes | Thin-coat silicone, silicone-silicate, acrylic, mineral, dashed (pebbledash and spar), textured scraped, smooth | We bring colour charts and texture samples for each finish. |
| Other finishes | Brick slip (looks like real brick), stone effect, timber or composite cladding, fibre-cement boards, ventilated rainscreen cladding | Brick slip is the key finish for brick streets and conservation-sensitive areas. |
| Detailing | Window and door reveals, cills, eaves extensions, verges, downpipes, gas meters, satellite dishes, plinth and DPC detailing, fire breaks | Reveals, cills, eaves and meters are what make EWI look right — and keep the weather out. |
| System holders | Certified systems from holders such as K Rend, Weber (webertherm), Sto (StoTherm), Wetherby, Parex, Baumit, EWI Pro and Alsecco | The system guarantee — up to 25 years with SWIGA or the system holder — comes from the system holder. Which system we use for your home, and the approved-installer status behind it, is confirmed in your quote. |
The system holder and guarantee for your job are confirmed in writing in your quote.
Which insulation?
EPS, mineral wool, phenolic, wood-fibre or cork
| Board | Thickness for the same performance | Fire | Breathability | Relative price | Best for |
|---|---|---|---|---|---|
| EPS (white or graphite) | Mid — graphite EPS is slimmer than white | Combustible — not for buildings 18 m and over | Low | Lowest | Most houses; the cost-effective default |
| Mineral wool | Mid — similar to white EPS | Non-combustible — required on taller buildings | High | Mid | Blocks of flats, taller buildings, fire-sensitive uses |
| Phenolic | Thinnest | Combustible — not for buildings 18 m and over | Low | Higher | Where reveals, eaves or boundaries limit thickness |
| Wood-fibre | Thicker | Combustible — not for buildings 18 m and over | High | Higher | Period and solid-wall homes that need to breathe |
| Cork | Thicker | Combustible — not for buildings 18 m and over | High | Highest | Natural, durable, breathable façades |
Fire safety on taller buildings
On residential buildings 18 m and over, combustible materials are banned in external walls, so only non-combustible insulation (mineral wool) and finishes are used. Buildings of 11–18 m follow Approved Document B and a fire risk appraisal. Cavity barriers and fire-stopping go in on every job.Finishes
Render, brick slip and cladding
K Rend silicone render
Through-coloured, self-cleaning silicone finishes — K1, Silicone TC15 and HP14 — on insulated K Rend systems or as a re-render.
K Rend renderBrick slip
Looks like real brick, performs like EWI — the key finish for brick streets and conservation-sensitive areas.
EWI with brick slipEvery finish we offer
Render finishes
Thin-coat silicone, silicone-silicate, acrylic, mineral, dashed (pebbledash and spar), textured scraped, smooth
Other finishes
Brick slip (looks like real brick), stone effect, timber or composite cladding, fibre-cement boards, ventilated rainscreen cladding
A separate service
Render without insulation
Re-rendering anyway?
The scaffold and the new finish are already part of the job, so it's the cheapest moment to add insulation underneath. Compare external wall insulation.- K Rend silicone through-coloured renderOne- or two-coat silicone render that cleans itself and never needs painting. Use: New render and re-render on block and brick.From £4,000
- Monocouche renderThrough-coloured single-coat cement render. Use: New builds, extensions.£50–£85 per m²
- Acrylic and silicone thin coatThin finishes over a base coat and mesh for a smooth modern finish. Use: Smooth modern finish, over boards.£50–£85 per m²
- Lime renderBreathable lime render and lime plaster for older solid walls. Use: Period, listed and solid-wall homes.Priced after survey
- Insulating (thermal) lime renderLime render with an insulating aggregate for modest U-value gains on old walls. Use: Listed and conservation properties where EWI is not allowed.Priced after survey
- Sand and cement, pebbledash and spar dashTraditional renders, repairs and re-dashing. Use: Repairs and like-for-like.Priced after survey
- Render repairs, removal and paintingHacking off failed render, crack repair, mesh reinforcement, masonry paint and render cleaning. Use: Maintenance and pre-sale.Priced after survey
Render-only work is standard-rated for VAT; insulation in homes is zero-rated.
Prices
What external wall insulation and render costs
| 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 |
| EWI with brick slip finish | £12,000–£20,000 | £18,000–£32,000 | £26,000–£45,000 | £16,000–£27,000 | £170–£280 per m² |
| Re-render only (K Rend silicone) | £4,000–£7,500 | £6,500–£12,000 | £9,000–£18,000 | £5,500–£10,000 | £55–£95 per m² |
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.
| Service | Typical range, installed |
|---|---|
| Render only (silicone, monocouche) | £50–£85 per m²plus scaffolding |
Indicative ranges for London and the South East, supplied and installed, including VAT. 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.How it works
Survey, check, install, guarantee
- 1
Survey
A surveyor visits, measures and checks the construction — borescope for cavities, moisture and ventilation for roofs — then confirms what suits your home and the final price.
- 2
Condensation risk and PAS 2035, where needed
Internal and external wall insulation and roof conversions get a condensation risk analysis for each build-up. Funded and whole-house jobs follow PAS 2035, starting with a retrofit assessment.
- 3
Install
We install to the manufacturer's or system holder's specification, with one named contact throughout. Scaffolding, making good and any building control are set out in your quote.
- 4
Guarantee and paperwork
You get the paperwork for what's installed — the guarantee from the relevant body or manufacturer, explained before you sign, plus any building control or competent-person certificates.
Grants and savings that may help
- ECO4Closes in 73 days
Up to fully funded; paid by energy suppliers per measure
Grant via local councils (£960m nationally in 2026/27)
- Social Housing Fund
Landlord-led bids
Saves 20% VAT
- Local schemes
Varies
Eligibility depends on your circumstances and is confirmed by evidence and the funder or council.
Grant schemes change often. Our 60-second checker uses the current rules and tells you plainly whether you're likely, possibly or not eligible — and we never call funded work free without saying it depends on eligibility.
Check my eligibilityQuestions
External Wall Insulation and Render: common questions
What's the difference between EWI and render?
EWI is insulation with a render or cladding finish on top; render on its own is just the finish. Both renew how the house looks, but only EWI keeps the heat in, lowers bills and improves your EPC.
Can EWI go on any house?
Most houses with solid or hard-to-treat walls can have it, subject to planning and access. Mid-terraces never get side-wall EWI because they have no side wall, listed buildings need consent, and blocks of 18 m and over must use non-combustible insulation only.
How long does external wall insulation last?
A well-installed certified system is designed to last for decades, and system guarantees of up to 25 years are available through the system holder or SWIGA. Your guarantee is confirmed in writing in your quote.
Can I have new windows at the same time?
Yes, and it's the best time to do it: new windows are set to line up with the insulation, the reveals are insulated properly, and you have one scaffold and one contract with LINX Glass.
Begin your project
Price your insulation in two minutes
Prices by property type, with grants and 0% VAT applied where they fit. A survey always confirms the final figure.