Party wall cavity 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 about 6 miles south-west of Bangor.
A suitable wall in Caernarfon is usually filled in a single day from outside, with drill holes made good to match the pointing. 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.
Before any material is chosen, exposure is checked. 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.
In terms of approvals, 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.
Why a party wall loses heat
Many semi-detached and terraced homes built with cavity separating walls have that cavity open to the loft. Air moves up the cavity and out at the top, a loss sometimes called the party wall bypass. Filling the cavity and sealing the top stops it.
What is included in Caernarfon
- Sealing at the top of the cavity
- Loft inspection and borescope check
- Written result and photos
- Neighbour notification guidance
Guide prices for Caernarfon
| Party wall cavity insulation guide prices | Guide price |
|---|---|
| Party wall, two-storey house | £595–£895 |
| Party wall, bungalow | £395–£695 |
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.
From enquiry to finish in Caernarfon:
Get in touch
Online, by phone or WhatsApp, whichever suits you.
Survey visit
The surveyor checks each wall and looks into the cavity where needed.
Your result in writing
What we found, what it means, and a fixed price if work is needed.
Booked work
Carried out by the installer named on your quote, with their scheme registrations.