Cavity insulation top-up for Derry properties
Derry is among the towns we cover in County Londonderry, alongside Limavady, Coleraine and Magherafelt. Derry is one of the main towns we cover in County Londonderry.
If a wall in Derry 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. Most Derry houses built from the 1920s onwards have cavity walls, but the survey still checks each one: cavity width, debris, the condition of the brickwork and how exposed each wall is.
Wind-driven rain is the first thing the surveyor weighs up. Parts of County Londonderry 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 Derry inserting cavity wall insulation needs a building control application to the council before work starts.
Funding in Northern Ireland
In Northern Ireland, the Affordable Warmth Scheme helps eligible households with a gross income under £23,000.
Sources: NI Housing Executive: Affordable Warmth Scheme; Utility Regulator: NI Sustainable Energy Programme.
When a top-up is not enough
If the existing fill is wet, contaminated with debris or breaking down, adding more on top can make things worse. In that case we tell you the honest option, which may be partial or full removal and refill.
What is included in Derry
- Making good
- Map of filled and empty sections
- Written result with photos
- Borescope survey at several points
Guide prices for Derry
| Cavity insulation top-up guide prices | Guide price |
|---|---|
| Detached house | £1,295–£2,295 |
| Semi-detached house | £795–£1,495 |
| End-terrace house | £695–£1,295 |
| Detached bungalow | £695–£1,295 |
| Semi-detached bungalow | £595–£995 |
| Mid-terrace house | £595–£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.
The steps for cavity insulation top-up in Derry:
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.