Mineral wool EWI · Wales
Mineral wool external wall insulation in South Glamorgan
We provide mineral wool external wall insulation across South Glamorgan, including Cardiff, Barry and Penarth, with a free survey and fixed written price. For homes in South Glamorgan near busy roads, mineral wool's sound reduction can be a reason to choose it.
- Free survey and fixed written price
- Guide price from £125 per m² + scaffold, 0% VAT
- Planning and building control checked for Wales
Free survey in South Glamorgan
Tell us the postcode and what you need.
What you get
- Finished in mineral or silicone render, or brick slip
- Used on blocks of flats and buildings with storeys above 11m
- Better sound reduction than foam boards
- Non-combustible board (typically Euroclass A1 or A2-s1,d0 as part of the system)
- Vapour-open, so moisture in solid walls can dry outwards
Homes and walls in South Glamorgan
South Wales has long runs of solid-wall valley terraces, Victorian and Edwardian town housing and post-war council estates.
Exposure to wind-driven rain varies across South Glamorgan: sheltered town streets fare better than walls on high ground or facing the prevailing weather, and the render, beads and cill details are chosen with that in mind.
Older solid-walled homes in South Glamorgan can suit a vapour-open mineral wool build-up better than foam; the survey checks the wall first.
- Nation
- Wales
- Region
- South Wales
- Towns covered
- Cardiff, Barry, Penarth
- Guide price
- From £125 per m² + scaffold · 0% VAT
Approvals in Wales
Permitted development rules for houses in Wales are similar to England's: a similar-appearance finish on a house is often permitted, while conservation areas, National Parks, Areas of Outstanding Natural Beauty, flats, commercial buildings and listed buildings need permission or consent. Your local planning authority has the final word.
The Building Regulations as they apply in Wales treat insulating or re-rendering more than half of a wall's area, or more than a quarter of the building's whole envelope, as renovating a thermal element, with Approved Document L (Wales) setting the target. Building control is involved before work starts.
Wales applies its own amended fire rules for external walls, including the combustible materials ban for relevant buildings and guidance for residential buildings between 11 and 18 metres, updated by the Building (Amendment) (Wales) Regulations 2025.
Why choose mineral wool over EPS?
Two reasons come up most: fire and moisture. Mineral wool doesn't burn, which is why guidance for taller residential buildings points to non-combustible external wall materials. It is also vapour-open, so a solid wall that holds some moisture can keep drying outwards through the insulation and render.
The trade-offs are weight and cost. Slabs are denser, need more fixings and take longer to install, so the price per m² is higher than EPS.
Mineral wool external wall insulation prices in South Glamorgan
| Item | Guide price | Notes |
|---|---|---|
| Mineral wool + mineral or silicone render | £125–£170 per m²0% VAT | Excluding scaffold |
| Mineral wool + brick slip | £195–£260 per m²0% VAT | Heavier slip systems need extra fixings |
| Three-bed semi, full house | £11,800–£20,2000% VAT | 80–100 m² of wall, including scaffold |
Confirmed by a fixed written quote after survey. 0% VAT: installing insulation in a home is zero-rated until 31 March 2027, so these figures are the total; 5% applies from 1 April 2027.
What happens next
Tell us about the property
Use the quote tool or form, or call. Photos help.
Free survey
We measure, check the walls and confirm approvals.
Fixed written quote
System, details, access, exclusions and VAT in writing.
Installation
Scheduled for suitable weather, with a clear programme.
Mineral wool EWI in South Glamorgan: questions
Is mineral wool better than EPS?
Not always better — different. Mineral wool wins on fire performance, breathability and acoustics; EPS wins on cost, weight and thinner boards for the same U-value. The wall, the building height and your priorities decide it.
Does mineral wool get wet?
It is water-repellent and protected by the render system. Like any insulation it must not be left exposed to rain during installation, so boards are covered and work stops in wet weather.
Can mineral wool EWI have a brick finish?
Yes. Brick slips can be bonded over mineral wool systems designed for them, with additional fixings for the extra weight.
Do you cover all of South Glamorgan?
Yes. We survey and quote mineral wool external wall insulation across South Glamorgan, including Cardiff, Barry, Penarth.
Do I need planning permission in Wales?
Permitted development rules for houses in Wales are similar to England's: a similar-appearance finish on a house is often permitted, while conservation areas, National Parks, Areas of Outstanding Natural Beauty, flats, commercial buildings and listed buildings need permission or consent. We check your address before quoting.