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Cavity wall insulationCavity wall suitability surveyCavity wall insulation removalCavity insulation top-upDamp investigation after cavity insulationBonded polystyrene bead insulationBlown mineral wool insulationParty wall cavity insulationBorescope cavity inspectionCavity wall insulation for landlordsGrant and funding checkLoft insulation
Cavity wall insulation across the UK

Warmer walls, checked properly before anyone drills

We survey your walls first, tell you in writing whether they can be filled and with what, and give you a fixed price. Filling, top-ups, removal of failed insulation and the repairs in between.

Get my free survey 0800 088 6248
  • Free survey with an install quote, and a written result for every wall
  • Registered installer and guarantee named on your quote before you book
  • No VAT on installing insulation in homes until 31 March 2027

Prefer a number first? Try the guide-price tool.

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Tell us about the property and we will arrange a 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.

Installer on a low platform filling the brick wall of a 1930s semi-detached house through a grid of drilled holes, with the delivery hose running to a van Filled from outside, usually in a day

What goes in the gap

Cross-section of a filled cavity wallOuter leaf of brick, a cavity filled with insulation, an inner leaf of block with plaster, and a wall tie crossing the cavity. Outer leaf (brick)Inner leaf (block)Cavity fillWall tiePlaster
  • Brick outer leaf
  • Cavity fill
  • Block inner leaf
  • Guarantee named on your quote
  • Free survey with an install quote
  • Installer and scheme registrations named
  • England, Wales, Scotland and NI
  • Fixed price in writing before work
Services

Everything to do with cavity walls

From a first fill to putting right a failed one. Choose a service for prices, what is included and how it works.

Insulate your walls

Fill an empty cavity, top up a patchy one, or insulate as you build.

Gloved hands holding an injection nozzle in a drilled mortar joint to fill a cavity wall

Cavity wall insulation

Survey, drill, fill and make good: an empty cavity filled with a certified system.

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Cutaway sample of a cavity wall: red brick outer leaf, cavity filled with blown mineral wool, concrete block inner leaf

Blown mineral wool insulation

Water-repellent mineral fibre blown into the cavity: the long-standing standard fill.

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Cutaway sample of a cavity wall filled with bonded white polystyrene beads between brick and block

Bonded polystyrene bead insulation

Expanded polystyrene beads coated with a binder so they lock together in the cavity.

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Row of red brick terraced houses with party walls rising through the roofline

Party wall cavity insulation

Seal the hidden cavity between you and next door that leaks heat into the loft.

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Technician inserting a borescope camera probe into a small hole in a buff brick wall

Cavity insulation top-up

Fill the gaps in an older, patchy or disturbed cavity fill without starting again.

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

Cavity insulation for new builds and extensions

Full-fill or partial-fill batts fitted as the walls go up, for builders and self-builders.

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Surveys and checks

Find out what is in your walls before anyone drills.

Surveyor measuring the wall thickness at a window reveal of a brick house

Cavity wall suitability survey

The check that comes before any drilling: walls, cavity, condition and exposure.

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Technician inserting a borescope camera probe into a small hole in a buff brick wall

Borescope cavity inspection

A camera through a small hole shows what is really in your cavity.

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Thermal imaging camera showing heat loss from the front of a semi-detached house at dusk

Thermal imaging survey

Infrared images that show where heat escapes: empty panels, gaps and cold bridges.

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Old cavity insulation drill holes, filled with mortar, spaced across a brick wall

Existing insulation and guarantee check

For buyers, sellers and owners: is the cavity filled, is it sound, is there a guarantee?

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Problems, removal and repairs

Damp, failed fills, debris and corroded ties, put right properly.

Old cavity insulation being extracted through bricks removed at the base of a wall, with sacks of extracted fibre

Cavity wall insulation removal

Extraction of wet, failed or unsuitable fill, with bricks lifted and reinstated.

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Installers refilling a cavity wall from a tower after extraction, with reinstated brickwork at low level

Remove and refill

Extract the failed fill, fix the cause, then refill with a system that suits the wall.

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Moisture meter held against a damp, mould-spotted corner of an external wall indoors

Damp investigation after cavity insulation

Find the real cause of damp before anyone recommends extraction.

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Bricks removed at the base of a wall so mortar debris can be raked out of the cavity

Cavity cleaning and debris removal

Clear mortar droppings and rubble that bridge the cavity and carry damp across.

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Drilling a mortar joint to fit a remedial stainless steel wall tie

Wall tie replacement

Remedial ties fitted where old steel ties have corroded and the outer leaf is moving.

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Repointing weathered brickwork with fresh mortar

Repointing and pre-insulation repairs

Pointing, brick, sill and gutter fixes that make a wall fit to fill.

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Landlords, housing and commercial

Portfolios, blocks, estates and commercial buildings.

Row of red brick terraced houses with party walls rising through the roofline

Cavity wall insulation for landlords

Portfolio surveys and fills that lift EPC ratings at the lowest cost per point.

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1970s low-rise housing estate of buff brick maisonettes and terraced houses

Social housing and estate programmes

Surveys, fills and remediation for housing associations and councils.

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Two-storey red brick office building on a business park

Commercial cavity wall insulation

Offices, schools, surgeries and light industrial buildings with masonry cavity walls.

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Three-storey 1960s red brick block of flats

Cavity wall insulation for flats

Whole-block surveys and fills, coordinated with freeholders and managing agents.

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Paperwork, a calculator and reading glasses on a kitchen table

Grant and funding check

A straight answer on whether a funded scheme could pay, before you pay privately.

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More insulation

The other quick wins that usually sit alongside a cavity fill.

Installer laying mineral wool loft insulation between ceiling joists

Loft insulation

Top up or replace loft insulation to current depths while we are on site.

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Lifted floorboards showing insulation fitted between suspended timber floor joists

Underfloor insulation

Insulate suspended timber floors from above or below without losing ventilation.

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Fitting a rubber draught-proofing strip to a front door frame

Draught-proofing

Seal gaps around doors, windows, letterboxes and loft hatches.

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How we work

Honest about walls that should not be filled

Survey first, not sales first

Every job starts with a wall-by-wall check. If a wall should not be filled, you get that in writing with the reason.

Removals and fixes too

Damp investigations, extraction, debris clearance and wall ties, so one team can put a failed fill right.

Straight answers on grants

We check what might fund your work and point you to the official route. No cold calls, no false promises.

Paperwork that stands up

Photos, the building regulations route, the installer and the guarantee, all named before you book.

The basics

What is cavity wall insulation?

Most UK homes built from the 1920s onwards have two walls with a gap between them. Cavity wall insulation fills that gap with a certified material blown in through small holes, so less heat escapes through the walls.

By the end of 2024 an estimated 71% of British dwellings already had cavity wall insulation, according to the government's Warm Homes Plan. The rest are a mix of homes that were never filled, homes that are not suitable, and fills that were missed in places or have failed.

That is why we start with the wall, not the sale: cavity width, debris, brick and pointing condition, damp and exposure to wind-driven rain all decide whether a wall should be filled, and with which system.

Is my home suitable? · Wool or beads? · Does it cause damp?

Cross-section of a filled cavity wallOuter leaf of brick, a cavity filled with insulation, an inner leaf of block with plaster, and a wall tie crossing the cavity. Outer leaf (brick)Inner leaf (block)Cavity fillWall tiePlaster
Guide prices

What does cavity wall insulation cost?

Guide ranges for a privately funded fill with bonded bead, the most common system we specify. Mineral wool is usually a little less. The Energy Saving Trust puts a typical Great Britain install at around £2,200.

Cavity wall insulation, bonded bead
Cavity wall insulation, bonded beadGuide price
Detached house£2,295–£3,795
Semi-detached house£1,495–£2,495
End-terrace house£1,295–£2,195
Detached bungalow£1,295–£2,195
Semi-detached bungalow£895–£1,595
Mid-terrace house£795–£1,395

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 after a free survey, before any work starts, and anything that could not be seen at survey is agreed with you first.

All prices: top-ups, removals, surveys and repairs →

What happens next

Four steps, no pressure

  1. Tell us about your home

    Postcode, house type and what you need. Takes a minute online or by phone.

  2. Free survey

    We check walls, cavity, condition and exposure, and photograph what we find.

  3. Written result and fixed price

    Suitable, suitable after repairs, or not suitable. Fixed price, installer, scheme registrations and guarantee named.

  4. Installation and paperwork

    Usually a day for a fill. You get the building regulations confirmation and guarantee details.

Questions

Cavity wall insulation FAQs

How much does cavity wall insulation cost?

On our guide ranges a private install runs from about £795 for a mid-terrace house to about £3,795 for a large detached house. The fixed price is confirmed in writing after a free survey, before any work starts; anything that could not be seen at survey is agreed with you before it changes the price.

Is there VAT on cavity wall insulation?

Installing insulation in a home is zero-rated for VAT until 31 March 2027, then 5%. Supply-only materials, most commercial work, and surveys, removal and repairs (which are not insulation) are standard-rated.

How do I know if I have cavity walls?

Homes built from the 1920s onwards usually have them. Brickwork with every brick laid lengthways and a wall over about 260mm thick at a window reveal both suggest a cavity. The survey confirms it.

Can every cavity wall be filled?

No. Narrow or dirty cavities, walls in poor repair, homes with undiagnosed damp, very exposed walls and flood-risk properties may not be suitable. We tell you in writing if a wall should not be filled.

Will I get a guarantee?

Your quote names the guarantee that will be issued and by whom, for example a CIGA 25-year guarantee where the installer is CIGA-registered. If a job cannot carry an independent guarantee, we tell you before you book.

Does cavity wall insulation cause damp?

Correctly specified and installed on a suitable wall, it should not. Problems come from filling unsuitable walls, defects that let rain in, debris in the cavity, or condensation.

More questions answered →

Coverage

Areas we cover

England, Wales, Scotland and Northern Ireland, with the rules and funding for each nation explained on every local page.

England

Wales

Scotland

Northern Ireland

Find out if your walls can be filled

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

Get my free survey0800 088 6248