Solid-wall houses leak heat through brick that was never built with a cavity to fill. External wall insulation (EWI) puts a board and a finish on the outside. Internal insulation is a different disruption and a different bill. This page prices the outside job. It is not an EPC, and it is not a decision that you qualify for help.
For the schemes that still exist, read ECO4 and the Great British Insulation Scheme. GOV.UK is the authority. This site does not decide eligibility. When you want a builder or an insulation contractor’s number, open building and place the call yourself.
Published UK bands
Checkatrade’s retrofit insulation guide, last updated July 2026, puts external wall insulation on a semi-detached house at about £10,000–£12,500. The same table puts internal solid-wall insulation lower, about £8,000–£10,000, because it avoids the scaffold and the outside finish. It cites the Energy Saving Trust for an annual saving in the low hundreds of pounds on a semi — a bill effect, not a payback promise from this site.
Other 2026 write-ups that cite the Energy Saving Trust put a typical three-bed semi nearer £14,000–£15,000 installed, with detached houses higher and small terraces lower. The spread is the point: wall area, finish and access move the total more than a single national average.
| What the guide describes | Published band | Source |
|---|---|---|
| EWI, semi-detached house | £10,000–£12,500 | Checkatrade, July 2026 |
| Internal solid-wall insulation, semi | £8,000–£10,000 | Same Checkatrade table |
| EWI, typical 3-bed semi, other EST-cited figures | about £14,000–£15,000 | 2026 summaries citing Energy Saving Trust |
GOV.UK has also warned about quality issues with some solid-wall insulation fitted through government schemes. A cheap installed price that skips window reveals, sills and rainwater goods is how those failures start. Price the detailing, not only the board.
Conservation streets cost more than the board
London conservation areas and listed façades can need planning even when the system is “just insulation”. A render colour and a thicker wall at the boundary are planning facts, not extras you discover on day three. Open builders in London and ask who applies.
Manchester and Birmingham red-brick terraces are the stock EWI was designed for, but party walls, shared rainwater goods and tight streets still need a written method. Leeds stone and Edinburgh ashlar are not the same substrate as a 1930s semi in Nottingham. Glasgow sandstone and close access can make internal insulation the only conversation a listed building will allow. Cardiff and Leicester mid-war semis sit closer to the Checkatrade semi band if the finish is standard render and the scaffold can stand for the job.
What moves the price
- Wall area and storeys. A detached house is not a mid-terrace gable.
- Finish. Thin render is not brick-slip cladding.
- Openings. Every window and door needs a reveal, a sill and a seal.
- Rainwater and roof edges. Gutters and soffits often have to move outward.
- Scaffold time. Shared pavements and parking bays add licences in cities.
Internal insulation avoids the scaffold and steals room width. It is the better comparison on a listed street, not a cheaper version of the same job.
A scheme name is not a discount on this page
The Great British Insulation Scheme’s eligibility checker has closed. GOV.UK says installations under that scheme had to be complete by 31 March 2026. ECO4 remains a supplier obligation with an end date of 31 December 2026. Neither fact turns a £12,000 quote into zero for every reader. Read the ECO4 page and the GOV.UK energy-company-obligation page before you treat a flyer as an approval.
This site does not enrol you on a scheme and does not check your benefits. A listing is a name and a number, not an installer appointed by a supplier.
What to have on the call
Have the wall type if you know it (solid brick, stone, already rendered), whether the house is in a conservation area, and whether anyone has already mentioned ECO4. Ask for a written system name, insulation thickness, finish, window detailing, rainwater, scaffold and VAT. Ask what guarantee is on the system, not only on the labour.
This site does not email the contractor. Open building in Manchester, Birmingham or Leeds and use the number on the card.
Questions before you treat this as a bill
How much does external wall insulation cost in the UK?
Checkatrade’s July 2026 guide puts EWI on a semi at about £10,000–£12,500. Other 2026 Energy Saving Trust citations sit nearer £14,000–£15,000. Detailing, finish and access move the total. A figure here is not a quote from this site.
Can I still get GBIS for EWI?
GOV.UK says the Great British Insulation Scheme checker has closed and installations had to be complete by 31 March 2026. Do not treat a closed scheme as a live discount. Read the ECO4 page for what is still open.
Does EWI need planning permission?
Sometimes. Conservation areas, listed buildings and a change of appearance can need consent even when the job is insulation. Ask the local planning authority, not this site.
Where do I find a contractor?
Open a building city list and use the phone number on the profile. This site does not send your job or apply for a grant.
Need a builder’s number?
Open building and conversions, pick the city, and contact the business yourself.