External Wall Insulation Cost: 2026 Prices Per m2 UK
Many older UK homes were built with solid walls, with no cavity to fill. Heat passes straight through them, which is why older terraces and Victorian semis can feel cold and cost a fortune to heat. External wall insulation (often shortened to EWI) wraps the outside of the house in a layer of insulation, then covers it with render or cladding. It cuts heat loss, gives the house a fresh new face and does not take any space from the rooms inside.
It is also one of the more expensive home upgrades you can make. In 2026, external wall insulation costs around £175 per m² installed on average, which puts a mid terrace at about £6,000 to £10,000 and a large detached house at £20,000 to £30,000 or more.
This guide explains what you will pay per square metre and by house type, what drives the price up or down, when you need planning permission, and what grants are still available.
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Prices
Most installers price external wall insulation per square metre of wall. The price includes the insulation boards, fixings, mesh, render or cladding, and labour.
| Item | Lower range | Higher range | Average |
|---|---|---|---|
| Total installed cost per m² | £150 | £200 | £175 |
| EPS (expanded polystyrene) per m² | £145 | £195 | £170 |
| Mineral wool per m² | £155 | £205 | £180 |
| Foil faced insulation boards per m² | £150 | £200 | £175 |
| Phenolic foam per m² | £150 | £200 | £175 |
| Removing existing external wall insulation per m² | £30 | £40 | £35 |
Checked October 2026: Checkatrade, External wall insulation cost: 2026 UK guide (table last updated July 2026). Prices include VAT.
Working out your wall area
To estimate your own job, measure the outside walls you want to insulate:
- Multiply the length of each wall by its height.
- Add the walls together.
- Take off large openings such as patio doors and big windows. Many installers leave smaller windows in the measurement because the reveals around them take extra work.
- Multiply by the price per m².
Example: a semi-detached house has three exposed walls totalling about 100m² after openings. At £175 per m², that is about £17,500, which matches the typical semi-detached figure below.
By house type
The number of exposed walls matters as much as the size of the house. A mid terrace only has a front and a back. A detached house has four walls to cover.
| Property type | Lower range | Higher range | Average |
|---|---|---|---|
| Mid floor flat | £5,000 | £7,000 | £6,000 |
| Mid terrace house | £6,000 | £10,000 | £8,000 |
| Semi-detached house | £14,000 | £20,000 | £17,000 |
| Detached bungalow | £15,000 | £21,000 | £18,000 |
| Detached house | £20,000 | £30,000 | £25,000 |
Checked October 2026: Checkatrade, External wall insulation cost: 2026 UK guide.
Flats are a special case. Insulating one flat in a block on its own rarely makes sense, because the insulation has to tie into the walls around it. Blocks are usually done as a whole, organised by the freeholder or council.
What is included
A full external wall insulation system is more than boards stuck to a wall. A typical installation includes:
- Scaffolding around the walls being insulated
- Preparation of the wall: removing loose render, treating any damp, repairing cracks
- Moving services such as satellite dishes, outside lights, pipes, gas meter boxes and alarm boxes
- Extending sills and roof edges so rain still drips clear of the new, thicker wall
- Fixing the insulation boards with adhesive and mechanical fixings
- Base coat and reinforcing mesh over the boards
- Finish coat of render, brick slip or cladding
- Beads and trims at corners, windows and the base of the wall
Check every quote for each of these. Two installers can quote very differently simply because one has included scaffolding and moving the downpipes and the other has not.
What affects the cost
Insulation material
The insulation board makes a difference to cost and performance:
- EPS is the most widely used option and usually the cheapest.
- Mineral wool has better fire performance and is the default choice for buildings over 11m tall under current building regulations guidance. It costs a little more.
- Phenolic foam and foil faced boards insulate well for their thickness, which helps where you want to keep the wall build up slim.
The finish
The finish is what you see. A standard silicone or acrylic render is the most common and cost effective option. Brick slips, timber effect cladding or stone finishes cost more but can keep the look of the street. If you are in a terrace where every other house is brick, a render finish may look out of place, and in some areas it may need planning permission.
Access and height
Three storey houses, homes on slopes, and walls next to conservatories or extensions are harder to scaffold and work on, which pushes the price up.
Wall condition
Cracked, damp or crumbling walls need repair before insulation goes on. Damp is especially important, because insulating over a wet wall can trap moisture in it. A good installer will survey the wall carefully and fix problems first.
Detailing
The fiddly parts take the time: window reveals, sills, roof edges, pipes and downpipes, and the junction with neighbouring houses. Houses with lots of windows, bays or ornamental features cost more per m² than plain walls.
Planning
Most external wall insulation falls under permitted development, so you do not need planning permission. The main exceptions are listed buildings and properties in conservation areas, where consent is likely to be required. Rules on appearance can also apply, especially if the new finish looks very different from the original walls.
Always check with your local planning authority before work starts. If you live in a conservation area or a listed building, involve the council early, because they may ask for a specific finish.
Building regulations
Building regulations apply when you renovate a large part of a wall. Checkatrade's rendering guide notes that if you replace or install render on 25% or more of the whole external walls, or 50% or more of any single wall, the wall insulation must be brought up to current requirements. External wall insulation is the usual way to do that on solid walls.
Your installer should notify building control or be registered with a competent person scheme. Ask for the completion certificate and keep it with your house documents.
Party walls and neighbours
The new wall will be thicker than the old one. On a terrace or semi, the insulation stops at the boundary, and the edge needs to be finished neatly. If the scaffolding needs to go on a neighbour's land, you need their permission. Talk to neighbours early.
Grants
Grant schemes for wall insulation have changed in 2026. The position as of October 2026:
| Scheme | Status |
|---|---|
| Great British Insulation Scheme | Ended on 31 March 2026 |
| ECO4 | Extended to 31 December 2026 for a managed closure, with limited new applications |
| Warm Homes: Local Grant (England) | Available through councils for eligible homes |
Checked October 2026: GOV.UK and Ofgem pages on the Great British Insulation Scheme, the government response on extending ECO4, and GOV.UK guidance on the Warm Homes: Local Grant.
The Warm Homes: Local Grant can fund wall insulation in England. Homes generally need an EPC rating of D to G, and households usually need an income of £36,000 or less, qualifying benefits, or to live in an eligible area. Councils run the scheme, so contact yours to check whether funding is still open.
Grant funded work is usually carried out by installers registered with TrustMark, who follow a set process including a retrofit assessment. That process takes time, so do not expect a grant funded installation within weeks.
Benefits
- Lower heat loss. Solid walls lose a lot of heat. Insulating them makes the house warmer and cuts heating bills.
- No loss of room space. Unlike internal wall insulation, nothing changes inside.
- Less disruption indoors. You can usually stay at home while the work is done.
- A new exterior. The finish can transform tired or patched brickwork.
- Protection for the walls. The render layer keeps rain off the original brick.
- Fewer cold spots. Covering the outside of the wall reduces cold bridging at floors and internal walls, which helps reduce condensation and mould inside.
Drawbacks
- Cost. It is one of the most expensive insulation upgrades.
- Appearance. It changes how the house looks, which matters in a street of matching houses.
- Detailing risk. Poor work around windows and roof edges can let water in behind the system.
- Planning limits in conservation areas and on listed buildings.
- Disruption outside. Scaffolding, noise and dust for a few weeks.
External vs internal wall insulation
If external insulation is not possible or too expensive, internal insulation is the alternative. It means fixing insulated boards to the inside of external walls, then plastering.
| Factor | External wall insulation | Internal wall insulation |
|---|---|---|
| Room size | No change | Each room loses some floor space |
| Disruption | Outside only | Rooms emptied, skirting, sockets and radiators moved |
| Appearance | Changes outside look | Outside unchanged |
| Planning | Sometimes needed | Usually not needed |
| Can be done room by room | No | Yes |
Internal insulation is often cheaper per m² and can be done one room at a time, which suits people renovating gradually. It works well in a listed building where the outside cannot change.
Cavity walls
If your home has cavity walls, filling the cavity is far cheaper than external insulation. Our cavity wall insulation guide covers costs and checks to make before filling. External insulation is mainly for solid walls, or cavity walls that cannot be filled.
How long it takes
A typical semi-detached house takes two to four weeks, depending on the weather. Render cannot go on in heavy rain or frost, so many installers prefer to work between spring and early autumn. The work breaks down roughly as:
- Scaffolding up
- Wall preparation and moving services
- Fixing insulation boards
- Base coat and mesh
- Finish coat
- Refitting services, then scaffolding down
An example cost build up
Here is how a quote for a typical 1930s semi-detached house might come together. The figures are illustrative, built from the average rates above, so use them to understand a quote rather than as a price.
| Item | How it is priced | Example cost |
|---|---|---|
| Wall area after large openings | about 100m² | |
| Insulation system and render, EPS | 100m² × £170 | £17,000 |
| Upgrade to mineral wool instead | 100m² × £180 | £18,000 |
| Removing an old, failed system first | 100m² × £35 | £3,500 extra |
Scaffolding, sills, moving services and the finish are normally inside the per m² price, but not always. If one quote is much lower than the others, check whether those items have been left out and will be added later.
Surveys and assessments
Before any external insulation goes on, the walls should be surveyed. A good survey checks:
- Whether the walls are solid or cavity, and their condition
- Signs of damp, and where it is coming from
- The state of existing render and pointing
- Roof overhangs, sills and how rain runs off the building
- Ventilation in the house, because a better insulated home needs good ventilation to manage moisture
- Gas flues, meters and other services that will need moving or extending
For grant funded work, the survey is part of a formal retrofit assessment. For privately funded work, it is still worth paying for a thorough survey, because fixing problems after the insulation has gone on is very expensive.
Ventilation after insulating
Insulating walls makes a house more airtight as well as warmer. That is good for bills, but moisture from cooking, showers and drying clothes has fewer ways to escape. Make sure extractor fans in the kitchen and bathroom work well, keep trickle vents open, and consider whether extra ventilation is needed. An installer who follows a proper retrofit process will look at this as part of the job.
Looking after the finish
Render systems need little maintenance, but a quick check each year keeps them in good shape:
- Look for cracks, especially around windows and at corners, and get them sealed.
- Keep gutters and downpipes clear, so water does not run down the walls.
- Clean off algae or dirt with a gentle wash, following the system maker's advice. Avoid harsh pressure washing, which can damage the surface.
- Do not drill into the system to hang baskets or satellite dishes without using fixings designed for insulated walls.
Questions to ask installers
- Which system will you use, and who makes it?
- What thickness of insulation, and what U-value will the wall achieve?
- Is the system warranty insurance backed, and for how long?
- What is included in the price, and what counts as an extra?
- How will you handle windows, sills, roof edges and the boundary with next door?
- Who arranges planning or building control sign off?
- How long will the scaffolding be up, and what happens if the weather turns?
Choosing an installer
- Look for installers who have done several jobs on homes like yours, and ask to see them.
- Ask which system they use and check that it comes with a system warranty, ideally insurance backed.
- Check membership of relevant trade bodies and, for grant funded work, TrustMark registration.
- Make sure the quote lists everything: scaffold, preparation, services, sills, finish and waste.
- Ask how they will deal with the junction with neighbouring properties and the roof edge.
If you are rendering rather than insulating, see our guide to rendering a house. For cladding finishes, see our house cladding guide.
FAQs
How much does external wall insulation cost per m²?
About £150 to £200 per m² installed in 2026, with an average around £175.
Does external wall insulation cause damp?
Not when designed and installed properly. Problems usually come from poor detailing that lets water in, or from insulating a wall that was already damp. A survey before work starts is essential.
How long does external wall insulation last?
A well installed system with a good render finish should last for decades. The render may need cleaning or recoating over time.
Can you insulate just the front of a house?
You can, but insulating every exposed wall gives a much better result and avoids cold spots where insulated and uninsulated walls meet.
Will external wall insulation add value to my home?
It improves the EPC rating, which can make a home more attractive to buyers, and a new finish improves kerb appeal. The effect on price depends on the local market.
Can I get a grant for external wall insulation?
Possibly, through the Warm Homes: Local Grant in England if your home and income meet the criteria. ECO4 is closing on 31 December 2026 with limited new applications.
Is external wall insulation noisy or messy?
There is some noise from drilling fixings and some dust while old render comes off, mostly in the first week. Inside the house, disruption is limited to moving things away from windows while sills are changed.
Can I stay in the house during the work?
Yes. Most people live at home throughout. You may lose the use of some windows for short periods while reveals and sills are finished.
Do I need to tell my mortgage lender or insurer?
It is sensible to tell your insurer, as it changes the construction of the walls. Keep all certificates and warranties for your lender and for when you sell.
Get quotes
Ask three installers to survey the house and quote for the same walls, the same insulation thickness and the same finish. A detailed written specification makes quotes easier to compare and protects you if something goes wrong.
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