Underfloor insulation for Porthmadog properties
Porthmadog is among the towns we cover in Gwynedd, alongside Caernarfon and Bangor. It is roughly 19 miles south of Bangor.
Small measures like this are often among the cheapest per pound saved, and they suit Porthmadog homes of every age. In Porthmadog homes this is often done on the same visit as a cavity fill, which saves a second trip.
As for paperwork, if cavity wall insulation follows in Porthmadog, 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.
Keeping the void ventilated
Air bricks under a suspended floor must stay clear so the timbers stay dry. Insulation goes between the joists, not across the void, and gaps at skirtings are sealed to stop draughts.
What is included in Porthmadog
- Boards relaid
- Draught sealing at skirtings
- Insulation between joists
- Floor void inspection
Guide prices for Porthmadog
| Underfloor insulation guide prices | Guide price |
|---|---|
| Suspended timber floor, typical room | £795–£1,495 |
| Whole ground floor | £1,995–£3,995 |
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.
What happens next for a Porthmadog property:
Tell us about the property
Postcode, property type and what you would like done.
Free survey
Access, condition, existing insulation and ventilation checked.
Written result and price
What we recommend and a fixed price before any work.
Work and tidy-up
Fitted at an agreed time, with ventilation kept clear.