External wall insulation · Gwynedd
External wall insulation in Caernarfon
From Caernarfon to Llangefni, we price external wall insulation after a measured survey — no guesswork, and no work starts until the price is agreed in writing. Whole-house jobs and single elevations are both quoted in Caernarfon; a cold gable or rear wall can be done on its own where it suits.
- Free survey in LL55 and nearby
- Guide price from £105 per m² + scaffold, 0% VAT
- Fixed written price before work starts
Free survey in Caernarfon
Postcode, service and a phone number is all we need.
What's included
- Cills, pipes, vents, meter boxes and the roofline detailed as part of the job
- Work happens outside, so you can live at home throughout
- Boards chosen for the wall: EPS, mineral wool, wood fibre or phenolic
- Typically takes a 225mm solid brick wall from around 2.1 W/m²K to about 0.30 W/m²K with 90–110mm of board
Homes and walls in Caernarfon
Surveys in Caernarfon also cover the surrounding LL55 district and towns such as Llangefni and Bangor (Gwynedd). Caernarfon is about 8 miles from Bangor (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 Caernarfon, the survey starts with the wall itself: solid brick, stone or concrete, and whether any old render is sound enough to insulate over.
- Postcode district
- LL55
- County or area
- Gwynedd
- Nation
- Wales
- Nearby
- Llangefni, Bangor (Gwynedd), Holyhead, Llandudno
Wales: planning and regulations
For homes in Caernarfon, the local planning authority decides any borderline cases; changing a brick house to render, or work on flats, usually needs an application in Wales.
Building control in Wales applies to most insulation and re-rendering jobs of this size; the quote states who submits the notice.
What does the survey check before EWI is specified?
- Wall construction and condition, including any damp, cracking or loose render
- Ground levels and the damp-proof course, so the system starts above splash height
- Eaves depth, verges and whether the roofline needs extending
- Window positions, cill depths and reveal space
- Services on the wall: gas, electric meters, flues, soil pipes, satellite dishes and lights
- Planning and Building Regulations position for your property and nation
External wall insulation prices in Caernarfon
| Item | Guide price | Notes |
|---|---|---|
| EPS system with silicone render | £105–£145 per m²0% VAT | Most common choice for houses |
| Mineral wool system | £125–£170 per m²0% VAT | Non-combustible, vapour-open |
| Brick-slip finish over insulation | £185–£260 per m²0% VAT | Where a brick look is wanted |
| Three-bed semi, EPS + silicone (incl. scaffold) | £10,200–£17,7000% VAT | 80–100 m² of wall; depends on detailing and access |
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
Enquiry
Send your postcode and a few details.
Measured survey
Walls, damp, eaves, cills and services recorded.
Written price
A fixed price with the specification attached.
Work and handover
Installed, inspected and documents handed over.
External wall insulation in Caernarfon: questions
Does EWI need Building Regulations approval?
In England and Wales, usually. Insulating more than half of a wall's area, or more than a quarter of the building's whole external envelope, counts as renovating a thermal element, so building control needs to be involved and the wall should reach about 0.30 W/m²K where that's practical. Scotland and Northern Ireland have their own building standards processes.
Does external wall insulation cause damp?
Not when it is specified and detailed properly. Problems usually come from poor detailing: no starter track above the damp-proof course, gaps at cills and penetrations, or a vapour-closed system on a wall that needs to breathe. The survey checks moisture, ground levels and the wall type before a system is chosen.
Can EWI go over pebble dash?
Usually yes. The dash is tested for adhesion and hollow areas; sound dash can be insulated over with additional mechanical fixings, while loose areas are removed first.
Do you cover Caernarfon?
Yes — we survey and quote external wall insulation in Caernarfon (LL55) and nearby Llangefni, Bangor (Gwynedd) and Holyhead, with a fixed written price before any work starts.