External wall insulation: questions and answers
The questions we're asked most, answered plainly. If yours isn't here, call or send us a message.
Frequently asked questions
What is external wall insulation?
Insulation boards fixed to the outside of your walls, protected by a mesh-reinforced render, brick slips or cladding. It reduces heat loss without losing any room inside.
How much does external wall insulation cost?
Guide prices run from about £109 to £175 per square metre for the system and finish, plus scaffolding. For an average home that's about £8,595–£11,695 for a mid-terrace, £13,995–£19,195 for a three-bed semi and £20,495–£28,095 for a four-bed detached house, with VAT at 0% on homes.
Is the survey free?
Yes, for installation quotes, with no obligation. Condition reports on existing EWI are charged from £295.
How long does it take?
It depends on the size of the house and the weather: bungalows usually take one to two weeks on site, terraces two to three, semis three to four and detached houses four to six. Blocks of flats take longer.
Do I need planning permission?
On a house in England, often not if the finish looks similar to the existing walls. You do in conservation areas and other designated land, for flats, and for listed buildings. Wales, Scotland and Northern Ireland have their own rules, which we set out for your address.
Is building control approval needed?
Yes. In England and Wales EWI renovates a thermal element; Scotland normally needs a building warrant; Northern Ireland needs council approval. We arrange it.
Is VAT charged?
Installing insulation in a home is zero-rated for VAT until 31 March 2027, then 5%. Commercial work is standard-rated.
Can I stay at home during the work?
Yes. All the work is outside.
Will EWI cause damp?
Designed and detailed properly, EWI usually keeps walls warmer and drier. Existing damp is diagnosed and fixed first, and old lime-built walls get breathable systems.
What finishes can I choose?
Silicone or mineral render in many colours, pebbledash, brick slips or cladding, alone or combined.
Are there grants?
It depends on your nation and circumstances. See our grants guide for the schemes open in October 2026.
Which areas do you cover?
England, Wales, Scotland and Northern Ireland. Remote and island work is by arrangement.
How do I pay?
Our standard terms are a 50% deposit on accepting the quote, 40% on the first day of installation and 10% on satisfactory completion, all set out in writing.
Do you work on flats?
On low-rise blocks, commissioned by the freeholder or management company. We don't take on higher-risk buildings.
What happens to my downpipes, lights and satellite dish?
They are taken down and refitted on extended brackets, and gas meter boxes and vents are dealt with as part of the job.
Will my windows need changing?
No, but if you plan new windows, fit them first or at the same time so the reveals can be insulated.
What if my roof overhang is too small?
We include a roofline extension or trim detail so rain is thrown clear of the new wall face.
Who will I contract with?
Your contract is with S&K Property Investments and Improvement Ltd, part of the S&K Group, named on your quote.