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County Down · Northern Ireland

Cavity insulation for new builds and extensions in County Down

For new walls the cavity is insulated as it is built, using full-fill mineral wool batts or partial-fill boards fixed to the inner leaf. Our County Down coverage includes Bangor, Newtownards, Newry and the towns around them.

Bricklayer building a new cavity wall with mineral wool batts between the block and brick leaves

Free survey in County Down

Tell us about the property and we will arrange a free survey and a fixed price.

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We use your details only to answer this enquiry and arrange your visit, sharing them only with the registered installer we appoint for your job and the providers named in our privacy notice. No marketing lists, no cold calls.

Cavity insulation for new builds and extensions across County Down

We cover 5 towns in County Down: Bangor, Newtownards, Newry, Downpatrick and Banbridge.

Every elevation is judged on its own exposure. Parts of County Down 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.

Most County Down 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. For semi-detached and terraced homes in County Down, cavity barriers are fitted where your wall meets your neighbour's so the fill stays on your side.

Building control in Northern Ireland

In Northern Ireland, inserting insulation into an existing cavity wall needs a building control application to your council before the work. We make sure the application route is agreed and confirmed in writing before any drilling starts.

Funding in Northern Ireland

  • The Affordable Warmth Scheme, run with the NI Housing Executive, helps owner-occupiers and private tenants with a total gross household income under £23,000; cavity wall insulation is a priority measure where suitable.
  • The NI Sustainable Energy Programme funds energy efficiency schemes through participating providers.
  • ECO4 does not apply in Northern Ireland.

Sources: Building Control NI: frequently asked questions; Belfast City Council: what are the building regulations; NI Housing Executive: Affordable Warmth Scheme; Utility Regulator: NI Sustainable Energy Programme.

Extensions that join an older house

Where an extension meets an existing cavity wall, the junction is a weak point. We can borescope and fill the existing wall at the same time so the old and new walls perform together.

What is included

  • Batts or boards to the specified U-value
  • Clean-cavity working
  • Trays, closers and stop ends as drawn
  • Coordination with your bricklayers
  • Photo record for building control

Cavity insulation for new builds and extensions prices in County Down

Cavity insulation for new builds and extensions guide prices
Cavity insulation for new builds and extensions guide pricesGuide price
Full-fill batts supplied and fitted, per m²£9–£16
Partial-fill boards supplied and fitted, per m²£14–£26

Prices are shown before any VAT; the VAT treatment for new-build work is confirmed on your quote. 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 County Down:

  1. Tell us about the property

    Postcode, property type and what you need.

  2. Free survey

    Walls, cavity, condition and exposure checked and photographed.

  3. Written result and price

    Suitable, suitable after repairs, or not suitable, with a fixed price.

  4. Work and paperwork

    Installation, making good, and the regulations and guarantee paperwork.

Last reviewed 19 October 2026.

Cavity insulation for new builds and extensions in County Down: questions

Do you cover all of County Down?

Yes. We cover 5 towns across County Down, including Bangor, Newtownards, Newry and Downpatrick, and the villages around them. Island and remote addresses are surveyed by arrangement.

How much does cavity insulation for new builds and extensions cost in County Down?

Our guide ranges for cavity insulation for new builds and extensions are shown on this page. The fixed price for your County Down property is confirmed in writing after the survey, before any work starts.

Do you cold-call in County Down?

No. We only come out when you have asked us to. If someone cold-calls offering free insulation, check before you agree to anything.

Is the survey free in County Down?

Yes when it is for an install quote. Standalone reports for County Down buyers, sellers or landlords who do not need an install quote are priced before you book.

Cavity insulation for new builds and extensions in nearby areas

Book a free survey in County Down

Free survey with an install quote. Written result. Fixed price before any work.