Cost of having Cavity Wall Insulation

All you need to know about having your cavity wall insulated including costs of materials, costs of labour and time frames.

cavity wall insulation

What the job entails

A typical cavity wall insulation job would entail a full property inspection to see if there is already cavity wall insulation or to check if the building is suitable for this type of work. To inject the insulation 20mm holes are drilled every metre throughout the wall and the insulation material is then blown into the cavity using a pressure gauge to check enough insulation has been inserted. Finally all the holes that were drilled will be filled with cement and the area will be tidied up (but the cement repairs are not normally painted) a certificate or letter confirming the work has been completed will be left.

The cement covering the holes drilled will usually need to be painted to match the exterior, so if the exterior of your home is looking a bit dowdy, this would be a good time to hire an external painter, rather than just touching up after the cavity insulation. If any re-pointing needs done it also may be worth having that taken care as well.

Most houses are suitable for cavity wall insulation, but if you have concrete gutters then leaks may result in the cavity wall insulation becoming soaked which can lead to damp patches internally and externally. So concrete gutters will need to be first lined to prevent rainwater leaking into the cavity wall. Properties in extremely exposed location may not be suitable due to the fact that wind driven rain may seep into the cavity, again leading to damp.

Obviously houses which do don’t have any cavity at all, solid wall structures, cannot have insulation injected! Plus timber or metal framed homes cannot have cavity all insulation injected, you need brick or masonry walls with a cavity of at least 50mm and no current damp problems. In addition the brickwork or masonry of your property has to be in good condition, otherwise the injection of insulation material could cause damage.

Local councils and power companies often have promotions which will pay for some or all of the cavity wall insulation costs, so always check your local council’s website along with your energy suppliers for any offers. If your home is less than 10 years old it is almost certain that you will have cavity wall insulation already installed.

If your property was built after 1920 but prior to the 1980's, then it almost certainly has a suitable wall cavity for insulation, however if built prior to this then it is likely a solid wall, so the only alternative to reduce heat loss through exterior walls is to consider a wall coating applied to the external walls of the house. If built during the 1980's onwards, you likely already have insulation in the form of rigid foam boards.

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Cavity Wall Insulation Cost

It will obviously vary depending on the property size, access and location. However, for a typical cavity wall insulation job on a 3-bed semi detached house it will normally cost around £500. But remember that many gas/electric suppliers and local authorities will offer discounts for loft and cavity wall insulation, particularly for those on low incomes or benefits.

So check with your council and energy suppliers for any promotions. Under the Energy Company Obligations scheme, energy suppliers will offer free grants for people who get tax credits and have an income of £16,010 or less, or those who are receiving certain other benefits.

The Energy Company Obligations (ECO) scheme legally requires energy suppliers to install energy efficient technologies to domestic households in the UK. If they fall short of their obligations they can receive hefty fines. They could pay for loft and cavity wall insulation up to around £700 combined! Even if you do not think you will qualify for help, it is worth double checking as some suppliers give free insulation away to all suitable homes in their regions regardless of income (this is becoming more common as energy companies struggle to meet targets and reduce the eligibility criteria).

Cavity insulation specialists don't tend to charge by the day, normally just by the size of the job. Depending on how many external walls your house has, the job should take around 2-4 hours.

Here are a few average costs for hiring a company to insulate your cavity walls:

House Type Scaffolding? Avg. Cost Duration
Terraced No £400 1-2 hours
Semi-detached No £500 2-3 hours
Detached No £600 3-4 hours
Terraced Yes £500 2-3 hours
Semi-detached Yes £600 3-4 hours
Detached Yes £700 4-5 hours

Cost Breakdown

Individual costs for hiring a specialist company to install cavity wall insulation into a 2-storey semi-detached house with easy access - Total Cost: £500


Materials & Equipment






Typically around 2 hours for a standard semi detached 3 bed house. However this price assumes good access with no scaffold required. The job is not particularly messy or disruptive, though there will be some vibration so fragile items should be moved/covered. There will also be a fair amount of dust externally, so keep doors and windows closed while drilling is in progress!
The holes used to inject the insulation material will be filled with cement. For brick walls this can often be left as is, but if you have rendered walls the cement you will likely prefer the cement to be painted so it matches the house exterior. This painting won’t normally be done by the cavity wall insulators as part of the job and is not included in the price, any painting will have to be arranged by yourself. It can be difficult to match the colour of the exterior, so consider repainting the entire wall.
According to the Energy Saving Trust, approximately a third of heat loss in an uninsulated home will be through the exterior walls. The expected savings can be anything from £90 per year (for a flat), up to around £275 per year for a typical 3 bedroom detached home. These figures are based on a home with gas central heating and no existing cavity wall insulation.
Flats can have cavity wall insulation installed in the same way but you need permission from all of the adjoining properties that share the same cavity walls. If there are costs involved then this can be troublesome if even one owner does not give permission.