Bonded polystyrene bead insulation across Gwynedd
We cover 4 towns in Gwynedd: Bangor, Caernarfon, Holyhead and Porthmadog.
Every elevation is judged on its own exposure. 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.
Gwynedd properties with rendered or painted walls get a closer look at the outer finish, because cracked render can let rain behind it. If a wall in Gwynedd 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.
Building Regulations in Wales
In Wales, filling an existing cavity is also notifiable building work under the Building Regulations as they apply in Wales. A registered installer normally self-certifies it through a competent person scheme; otherwise a building notice goes to your council's building control before work starts. Welsh rules can differ from England's, so the notification route is confirmed in writing on your quote.
Funding in Wales
- Warm Homes Nest offers free improvements, including insulation, to eligible low-income owner-occupiers and private renters; eligibility was widened to some households without means-tested benefits.
- Green Homes Wales has been piloting advice and interest-free loans for households above the Nest and ECO4 income thresholds.
- ECO4 runs until 31 December 2026 across Great Britain, including Wales.
Sources: Welsh Government: building work competent person schemes; CIGA: CWISC competent person scheme; Welsh Government: issues arising from cavity wall insulation installations; Welsh Government: warmer and more energy efficient homes (July 2026); GOV.UK: extending the ECO4 end date, government response.
What to know before you choose beads
Polystyrene is combustible, so beads are not the right choice for every building; height, use and nearby openings matter, and the system certificate sets the limits. PVC-sheathed cables in the cavity should be sleeved or kept out of contact with the beads where the certificate requires it. We check both at survey.
What is included
- Certified bonded bead system
- Binder applied at the nozzle
- Making good to the mortar colour
- Cable and opening checks at survey
- Regulations route and guarantee named on the quote
Bonded polystyrene bead insulation prices in Gwynedd
| Bonded polystyrene bead 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.
How it works in Gwynedd:
Send your details
A minute online, or call the free number.
We check the walls
Construction, cavity width, debris, damp and wind-driven rain exposure.
You decide
Plain-English result and a fixed price, with no pressure to book.
Job done properly
Holes made good, paperwork handed over, guarantee details confirmed.