Cavity wall insulation for flats across South Glamorgan
We cover 3 towns in South Glamorgan: Cardiff, Barry and Penarth.
Local weather affects which walls can be filled. Parts of South Glamorgan 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.
Work on South Glamorgan rented homes and blocks is booked around tenants and residents, with access arranged through your agent if you prefer. For landlords and managing agents in South Glamorgan, we survey in batches and return a result sheet and fixed price per address.
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.
Why one flat cannot usually be done alone
The cavity runs continuously across the building. The Energy Saving Trust notes that flats need agreement from the whole block. Filling one flat's walls in isolation leaves gaps, and the freeholder normally owns the structure.
What is included
- Block survey
- Freeholder and agent coordination
- Leaseholder information sheet
- Per-flat pricing
Cavity wall insulation for flats prices in South Glamorgan
| Cavity wall insulation for flats guide prices | Guide price |
|---|---|
| Per flat, whole-block fill (low-rise) | £495–£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 South Glamorgan property:
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.