Cavity wall insulation for Caernarfon properties
If your property is in Caernarfon or the LL55 district or nearby Bangor, Porthmadog and Holyhead, it is within our Gwynedd coverage. It is around 6 miles south-west of Bangor.
For semi-detached and terraced homes in Caernarfon, cavity barriers are fitted where your wall meets your neighbour's so the fill stays on your side. If a wall in Caernarfon is not suitable, for example because of an undiagnosed damp patch or a very exposed gable, you are told so in writing with the reason.
Exposure matters for every cavity wall. Parts of Gwynedd face some of the heaviest wind-driven rain in the UK, especially exposed coastal and upland sites. Here the survey is stricter: some walls suit only certain certified systems, and some should not be filled at all.
On the rules side, in Caernarfon filling a cavity is notifiable work under the Building Regulations as they apply in Wales, usually self-certified through a competent person scheme.
Funding in Wales
In Wales, Warm Homes Nest offers free improvements to eligible low-income households, and ECO4 runs to 31 December 2026.
Sources: Welsh Government: warmer and more energy efficient homes (July 2026); GOV.UK: extending the ECO4 end date, government response.
What happens on the day?
Holes of around 22mm are drilled in the mortar joints in a set pattern, roughly a metre apart. The insulation is blown in from the bottom up until each section is full, then every hole is filled with colour-matched mortar. Air bricks and flues are protected, and a cavity barrier is fitted where your wall joins a neighbour's.
What is included in Caernarfon
- Building regulations route for your nation, confirmed in writing
- Drilling, filling and colour-matched making good
- Suitability survey with photos and a written result
- Cavity barriers at party walls
Guide prices for Caernarfon
| Cavity wall insulation guide prices | Guide price |
|---|---|
| Detached house | £2,295–£3,795 |
| Semi-detached house | £1,495–£2,495 |
| End-terrace house | £1,295–£2,195 |
| Detached bungalow | £1,295–£2,195 |
| Semi-detached bungalow | £895–£1,595 |
| Mid-terrace house | £795–£1,395 |
No VAT is charged on installing insulation in homes until 31 March 2027 (then 5%). Guide ranges only: the fixed price is confirmed in writing before any work starts, and anything that could not be seen at survey is agreed with you first.
The steps for cavity wall insulation in Caernarfon:
Tell us about the property
Postcode, property type and what you need.
Free survey
Walls, cavity, condition and exposure checked and photographed.
Written result and price
Suitable, suitable after repairs, or not suitable, with a fixed price.
Work and paperwork
Installation, making good, and the regulations and guarantee paperwork.