Mineral wool EWI · Wales
Mineral wool external wall insulation in Gwynedd
We provide mineral wool external wall insulation across Gwynedd, including Bangor (Gwynedd), Holyhead and Caernarfon, with a free survey and fixed written price. Older solid-walled homes in Gwynedd can suit a vapour-open mineral wool build-up better than foam; the survey checks the wall first.
- 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 Gwynedd
Tell us the postcode and what you need.
What you get
- Finished in mineral or silicone render, or brick slip
- Non-combustible board (typically Euroclass A1 or A2-s1,d0 as part of the system)
- Heavier than EPS, so more fixings and careful handling
- Vapour-open, so moisture in solid walls can dry outwards
- Better sound reduction than foam boards
Local considerations in Gwynedd
North Wales has many solid stone and slate-built homes, Victorian seaside terraces and post-war council estates.
Parts of Gwynedd fall in the higher wind-driven rain exposure bands, especially coastal and upland sites, so render specification, movement joints and detailing at cills, verges and the base of the wall matter more than usual.
For homes in Gwynedd near busy roads, mineral wool's sound reduction can be a reason to choose it.
- Nation
- Wales
- Region
- North Wales
- Towns covered
- Bangor (Gwynedd), Holyhead, Caernarfon, Llangefni
- Guide price
- From £125 per m² + scaffold · 0% VAT
Permissions 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.
What about noise?
Dense mineral wool adds mass and absorbs sound, so homes beside main roads or railways often notice a quieter interior, particularly where windows are also upgraded. The improvement depends on the whole wall and windows, so we don't quote decibel figures without testing.
Mineral wool external wall insulation prices in Gwynedd
| 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 Gwynedd: questions
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.
Is mineral wool needed for a bungalow?
Rarely for fire reasons. It may still be chosen on a damp-prone solid wall where a vapour-open build-up is wanted.
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 Gwynedd?
Yes. We survey and quote mineral wool external wall insulation across Gwynedd, including Bangor (Gwynedd), Holyhead, Caernarfon, Llangefni.
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.