Wall Cavity Insulation Cost

By Sam
Last updated 20th May 2024 - Reading time: 22 mins
At a glance
  • The average cost of wall cavity insulation is usually around £500
  • The job will usually take been 4-8 hours
In this article, you'll find out the following:
  • A breakdown of pricing information based on house sizes and other factors
  • How long the job should take and a general overview of what will be involved
  • How to find and hire a insulation contractor

Want to know how much it costs to insulate your cavity walls?

In this ultimate price guide, we provide a detailed breakdown of average wall insulation prices for different house sizes, cavity wall insulation installers, as well as costs for different types of cavity insulation like cavity wall insulation injection.

On average, the total cavity wall insulation cost will be around £500, typically.

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someone installing cavity wall insulation

Average Cost of Cavity Wall Insulation:

Depending on the complexity of the job, it usually takes: 4-8 hours


How Much Does Cavity Wall Insulation Cost?

The cost of cavity wall insulation depends on how much area needs filling on the type of insulation you choose. The main factor is the area to be filled. So really this means the kind of home you have.

For a mid-terrace home, you can expect costs of £340-£400. For a Semi-detached house, the costs raise to £450-£500. A large detached home will cost around £700-£750.

If you have a fixed budget, then you should look into cavity wall insulation grants. These are available to some homeowners through energy suppliers. The grants can cover some or all of the cost to lay cavity wall insulation.

How beneficial to energy efficiency would cavity wall insulation be? What other advantages would it offer, aside from keeping my home warmer for less?

"In a nut shell, any insulation would reduce your heating energy consumption, and create a more balanced temperature throughout the home, also worth noting it would pay for itself very fast in just the savings you would make."

Cavity Wall Insulation Prices

These are the average cavity wall insulation costs. They assume that there is no insulation to be removed and that the whole job is uncomplicated.

House Type Average Cost
Mid Floor Flat £300-£350
Detached Bungalow £400-£450
Terraced £350-£400
Semi-detached £450-£500
Detached £700-£750
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Labour Costs and Timescales

House Type Duration Average Cost
Mid Floor Flat 1-2 hours £50-£100
Detached Bungalow 3-4 hours £150-£200
Terraced 2-3 hours £100-£150
Semi-detached 2-3 hours £100-£150
Detached 3-4 hours £150-£200
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Supply Costs

The supply cost for your insulation will depend solely on the insulation type, space needed to cover and the supplier that you choose. Below we have broken down some of the supply costs.

Insulation Prices

Insulation Type Average Cost per m2
Mineral Fibre £13-£18
Wool Fibre £25-£30
EPS – Expanding Polystyrene Beads or Granules £18-£22
PUR – Polyurethane Foam £22-£26
Cavity Wall Boards £15-£17
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Additional Costs

When you decide to get your cavity wall filled, there are a few other jobs you might want to consider doing as well. There are several options to improve the energy efficiency of your home to tackle once the walls are done. Some costs might arise that increase the cost of the cavity wall insulation installation.

Cavity Wall Survey Cost

Some installers will charge separately for a survey of the walls. If you don’t go ahead with the cavity wall insulation, then and there you will only pay for the survey. If you get the work done, most installers will bundle the cost of the initial survey into the cavity wall insulation prices. The survey usually costs around £75.


Cost of Replacing Wall Ties

The wall ties are what join the two layers of brick together. If the wall ties begin to fail, then you will see cracks in the mortar on the exterior wall. When the cavity wall is inspected before fitting the insulation, it may become apparent that the wall ties need to be replaced.

If this needs doing, you should consider doing it before you get the insulation installed. Fixing wall ties may cause some damage to the cavity wall insulation and reduce its efficiency. It costs between £1,000-£2,000 to replace your wall ties.

‘Hard to Treat’ Cavity

There are a few circumstances that can make it harder to install cavity wall insulation. For instance, if you have some insulation already in your walls, it may need to be removed or worked around. The same is true for debris within the cavity wall. The effect on the price for your cavity wall insulation will vary a lot depending on the exact circumstances. In a simple case, it may only add £50 in a more complex situation it could cost up to £1,500.

Heat Loss Survey Cost

If you are installing cavity wall insulation as part of an effort to make your home more efficient, then you might want to consider getting a heat loss survey. These use thermal imaging cameras to trace where heat is being lost from your home.

The results can then point you to the best changes to make to improve your home. The cost of these surveys varies widely. It depends on the level of scan you want and the size of the property. They usually start at around £200.

Roof Insulation Cost

Once you have reduced the heat lost through your walls you might want to consider the heat lost through the roof. Getting your roof insulated is a reasonably simple job. It usually costs between £450-£800 depending on the size of your roof.


Loft Insulation Cost

Insulating your loft can save you between £115-£215 per year. Which makes it a good investment. IF you use a similar type of insulation as for your cavity wall, you might be able to get a discount from your installer. Typically, it costs £400 - £600 to insulate your loft.

Cost of New Windows

If your windows are in poor condition, then you might want to consider replacing them. Poor seals, warped frames and blown double glazed windows, can all contribute to heat loss from a home.

It costs around £3,750 to fully replace all the windows in a home. Just replacing the blown window glass is a much cheaper option at around £70 per window.

New Exterior Door Cost

Doors are another point of escape for heat from your home. They also impact on the security of your home, so it is worth investing in high-quality doors. To replace a front door costs on average, £500.

Draught Proofing Cost

Draughtproofing is a great and cheap way to reduce your energy bills. It is a good DIY job, or you can get a professional to draughtproof your whole house for around £200.

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Cost Factors of Cavity Wall Insulation

The average cost of cavity wall insulation depends on only two factors.

The main factor is the area that needs filling. Cavity wall insulation prices depend primarily on the area to be filled. So, the more external walls you have, the higher the cost will be.

The second factor is the cost of wall insulation. The type of insulation you choose will affect the final price. The most expensive options are PUR (£22 - £26 per m2) and Sheep’s Wool (£25 - £30 per m2).

At the cheap end of the scale is Mineral Fibre (£13 - £18 per m2) and cavity wall boards at (£15- £17 per m2).

What's Involved in Installing Cavity Wall Insulation?

Before the insulation is fitted, the installer will carry out a survey. This is to check if your walls are suitable for insulation, and that there is not already insulation in place. They will also check the condition of the brickwork and for signs of damp.

The method for installing cavity wall insulation is relatively straight forward. A series of small holes are drilled into the exterior of your property. The insulation material is then blown into these holes using a pump. Once the cavity is filled, the holes are fixed and covered. The holes are filled, so they match the exterior of your home as closely as possible.

You should expect to receive a guarantee for the work. It usually comes in the mail not long after the work is completed. You may also receive a visit from an inspector. They may need to check that the work was completed to a good standard.

What is Cavity Wall Insulation?

Cavity wall insulation is used to store heat between the inner walls, which then gravitates to the adjuring rooms, warming up the property and getting rid of any draughts. The cavity can be found between the outer and inner brick walls of the house, and this is where the insulation is installed.


Can I Install Cavity Wall Insulation Myself?

Installing cavity wall insulation is not a job you should do yourself. Even if you are a seasoned DIYer, you should not take on this job. The work needs to be completed by a registered installer. Cavity wall insulation is covered by building regulations.

Can I Have Cavity Wall Insulation?

Since cavity wall insulation can have such a significant impact on energy bills, it is the first thought for many people when they want to insulate their homes. However, not all homes are suitable for cavity wall insulation. Three main questions need to be answered first.

Do I Have A Cavity Wall?

To have cavity wall insulation fitted, you must have a cavity wall. Not all homes do. Here are a few ways to identify if you have a cavity wall or not.

Brick Patterns

If you look at the way the bricks on you home are laid, you can identify if the wall is likely to have a cavity or not. If all of the bricks are laid lengthways, then you probably have a cavity. If the bricks alternate between being long side on and short side on, then there will be no cavity in your wall.

Age of Your House

Knowing the age of your home can help you identify if you are likely to have a cavity. Homes built after 1920 were almost always built using cavity walls.

The cavity walls were used to stop moisture getting into the home, so they were not usually insulated. In 1970 some builders began to add insulation as standard practice, but it wasn't expected until the 1990s.

So, homes built between 1920 and 1970 were built with cavity walls and no insulation. Home constructed between 1970 and 1990 might have insulation. Homes built after 1990 should have cavity wall insulation.


Thickness of Your Walls

If you have a cavity wall, then there will be a more considerable distance between the exterior wall and the interior surface. The best place to see this is in the windows. If the windowsill is very narrow, less than about 250mm, then you won’t have a cavity.

If you are uncertain, you can drill through the wall to be sure. You will be able to feel where if there is a cavity because the drill will go slack after the first course of bricks, and then pick up again when it meets the second course.

Is My Cavity Wall Suitable For Insulation?

Once you have identified whether or not you have a cavity wall, you will need to determine if it is suitable for insulation. There are a few factors that affect this.

Size of Gap

The cavity between the walls must be big enough for the insulation to fit. The gap must be larger than 50mm. In older homes, this might not be the case. You can check by removing a brick and measuring the distance to the interior wall. Or you can drill a hole and measure from there.

State of the Wall

The exterior wall must be in good condition. If it has cracks or the bricks are sagging, then cavity wall insulation would not be a good idea. If your exterior wall is not weatherproof, adding cavity wall insulation may lead to damp problems inside your home.

Does My Home Already Have Cavity Wall Insulation?

There are two ways to find out if you have cavity wall insulation. The first is to look inside the cavity wall. You can do this either by drilling a hole or by removing a brick.

The second option is to speak to the local council. They should have a record of all the homes that have ahs cavity wall insulation fitted.

Should I Have Cavity Wall Insulation?

For a small number of properties, it is not always appropriate to have cavity wall insulation, even if the cavity is suitable. This is because, in the wrong conditions, cavity wall insulation can lead to damp issues in a home.

The problem may only affect one of your walls, but you should speak to your installer if you have any concerns.

The factors to be aware of are:

  • Homes that are exposed to severe wind-driven rain (usually along the West coast of the UK).
  • Homes that are unsheltered by other houses or trees.
  • Homes with external walls in poor condition.

If more than one of these is true for your home, then make sure to seek advice about having cavity wall insulation fitted.

Building Permissions Needed for Cavity Wall Insulation

As long as your home is not listed, then there is no need to seek planning permission for cavity wall insulation. Especially if the work will make no change to the exterior appearance of the building, then planning permission is unnecessary.


You will need to submit a building notice. This is because cavity wall insulation is covered by building regulations, and it should be carried out at an expected standard. Most installers, especially if they are registered with the Cavity Insulation Guarantee Agency (CIGA), will take care of this. It is, however, the homeowner's responsibility to ensure that it happens.

Benefits of Cavity Wall Insulation

Having your cavity wall insulated brings all the benefits that any form of insulation does.

Reduces Energy Bills

If you heat your home, then adding cavity wall insulation will save you money. Without insulation, you will be losing heat from your home through the cavity wall. Without this heat loss, your central heating will not have to work as hard.

This means it will be on for less time every day. Thus, saving you money. Depending on your home it can save you between £70 and £245 per year.

Keeps Property Warmer

Some homes can feel chilly even when the heating is on. Cavity wall insulation can help with this. Once the cavity wall is filled, there will be less heat lost through the walls. This means that your central heating will only be heating the air in your home, so it will be able to keep things warmer.

Reduces Carbon Footprint

If you don't need to run your heating as much or as high as you used to then you will be using less fuel. You will also reduce the environmental impact of your home. So, as well as saving money, you'll be taking a step to save the planet.

Increase Property Value

Most homebuyers expect properties to be well insulated. By ensuring that your home is insulated, you will be making your home more appealing to future owners.

Because you have had the work done, you will take away any uncertainty about the start of the cavity wall. Given a choice between buying a home that has cavity wall insulation and one that might, it's an easy choice.

Type of Cavity Wall Insulation

Mineral Fibre Costs

Mineral fibres are made from molten rock. The molten rock is bound together and then either made into sheets or loose fibres. The average cost is £13 - £18 per m2.


✔ Can be blown into the cavity for easy installation

✔ Excellent insulating material

✔ Resistant to rot


✖ Not the most environmentally friendly option

Wool Fibre Costs

This is insulation made from sheep's wool. The wool can come as loose fibre or as rolls of wool, a little like a blanket. The average cost is £25 - £30 per m2.


✔ Good Insulating Material

✔ Can be blown into the cavity for easy installation

✔ A very eco-friendly option


✖ More expensive


EPS - Expanding Polystyrene Beads or Granules Costs

These are small beads or granules of polystyrene. There are easy to insert into the cavity. They provide excellent heat insulation and are environmentally friendly. The average cost is £18 - £22 per m2.


✔ Great Insulation Material

✔ Environmentally Friendly

✔ Damp Resistant


✖ Poor Sound Insulation

PUR - Polyurethane Foam Costs

This is a type of spray foam. It is excellent for filling every crack and space in the cavity as it expands as it sets. However, it can't be recycled, and it is not environmentally friendly. The average cost is £22-£26 per m2.


✔ Most Efficient Insulator

✔ Easy Installation


✖ Expensive Option

✖ Not environmentally Sound

Cavity Wall Board Costs

These are boards of insulation that are designed to fit in a cavity wall space. They are mostly designed to be fitted when the house is built so they can be hard to retrofit. The average cost is £15-£17 per m2.


✔ Come in a range of sizes and materials to suit your needs.

✔ Low Cost


✖ Hard to Retrofit

Urea-Formaldehyde Foam

Urea-formaldehyde foam used to be the standard when it came to cavity wall insulation. However, problems with this material mean that it is no longer used. It fails over time, as the foam shrinks significantly.

As it shrinks, it releases formaldehyde gas, which is a toxic chemical. It should not be used. If you have this foam injected into your walls, you should investigate having it removed and replaced.

Cavity Wall Insulation Grants

There are grants available to cover the cost of wall insulation. But this still doesn’t mean you’re entitled to full free home insulation, not everyone is eligible for a full grant. To find out if you are eligible, you will need to check with your energy supplier.

If your energy supplier is part of ECO (Energy Company Obligation), then you can check if you meet their criteria for a grant. Most of the major energy suppliers have signed up. These include British Gas, EDF Energy, Eon, Npower, Scottish Power and SSE.

The criteria are a little different for each company, but they generally depend on how much money it would save if you got the insulation. If It doesn't save much, then they are unlikely to pay, if it makes a big difference, then they are more likely to give you the grant. The other major consideration is whether you receive any benefits.

If you are interested in getting a grant, the only way to know for sure is to speak to your energy provider. You should ring them up and ask to speak about an ECO grant, or about affordable warmth. They are two names for the same scheme.

Even if you are not eligible for a full grant, you might be able to get some support if your cavity is deemed 'hard to treat'. If the course of getting your insulation you begin to have issues, you should speak to your energy provider again, and see if they can help out. Free loft insulation can also be available, so it’s worth checking if you haven’t got loft insulation.

The government insulation grants are available under the Energy Obligation Scheme (ECO).

How Does Cavity Wall Insulation Work?

Heat is lost through your cavity wall in a process called convection. The air in the cavity wall is free to move around. When it is heated up, it rises to the top of your home until it can cool.

The hot air that moves up is replaced by cold air from outside. This creates a convection current. It's like a breeze moving through the cavity of your walls, and as it moves, it takes heat with it.

Cavity wall insulation stops the convection currents from forming. Instead of the cavity being filled with air, which can move freely, it is filled with another material. The added material traps the air and stops it from taking the heat away from your home.

How Much Can Cavity Wall Insulation Reduce Energy Bills By?

As much as 1/3 of the heat from a home is lost through the walls. This means that installing cavity wall insulation is one of the easiest and most cost-efficient ways to reduce your energy bills.

Depending on the type of home, you have it can reduce your energy bills considerably. For a terraced home, cavity wall insulation can reduce bills by between £70 and £85 per year. In a detached home, heating bills can drop by as much as £200-£245 per year.

How Long Does Cavity Wall Insulation Last?

If properly installed the cavity wall insulation should last for the lifetime of your home. As long as your installer is properly certified, you should receive a 25-year guarantee from the Cavity Wall Insulation Guarantee Agency (CIGA).

The only reasons cavity wall insulation would need to be removed were if it was improperly installed, or if it was allowing damp into your home. By choosing an installer who is certified by CIGA, you can be assured of proper installation.

The survey that should be carried out before the insulation is fitted should identify if damp will be a problem before the insulation is put in.

Cost of Removing Cavity Wall Insulation

There are a small number of instances where removing cavity wall insulation is necessary. These are situations where the insulation has failed or is allowing damp into your home. If urea-formaldehyde foam was used, then it should be removed for health reasons, as it releases a dangerous chemical over time.

Removing Urea Formaldehyde Foam

If you have urea-formaldehyde foam in your walls then finding a contractor who is willing to remove it can be difficult. To remove the urea-formaldehyde insulation, it must be broken down into dust.

This dust is then vacuumed out of the cavity. This can take some time. The whole house must be secured so that not of the dust gets into your home. This means all ventilation routes must be sealed, and the whole job must be carried out with care.

It may be necessary to vacate your home for the duration of the job. This can be an expensive process, and prices vary.

Removing Other Types of Insulation

Other forms of insulation are much easier to remove. The bricks at the bottom of your wall are removed, and the insulation is sucked or pulled out. It is not difficult, but it is time-consuming. The average cost for this is around £21 per m2.

Hiring a Cavity Wall Insulation Installer Checklist

As with hiring any tradesperson, there are a few things you should look out for when hiring cavity wall insulation installer. Here are some things to check

  • Any installer should be a member of one of the following professional bodies -the National Insulation Association (NIA), the Cavity Wall Insulation Guarantee Agency (CIGA) or the British Board of Agrément (BBA)
  • Check that the installer has agreed to a professional code of practice.
  • Find out if their work is eligible for the 25-year guarantee offered by CIGA.
  • Search for “cavity wall insulation installers near me” at MyJobQuote.


When did cavity wall insulation become compulsory?
Technically cavity wall insulation isn't compulsory. However, there are insulation standards that have to be met. These standards were raised in the 1900s, and it was around that time that most builders began to fit cavity wall insulation as standard.
Who is entitled to free cavity wall insulation?
The requirements are complex and depend on your home and personal circumstances. However, most people who receive benefits or are over the age of 60 are likely to be eligible. To check if you meet the criteria, speak to your energy supplier.
What is the best cavity wall insulation to install?
It depends on how you define best. The best quality insulator is PUR (Polyurethane Foam). The best value option is probably EPS (Expanding Polystyrene Beads or Granules). The best option for the environment is sheep’s wool.
How long until the cavity wall insulation pays for itself?
The exact payback time will depend on the on your home. However, most homeowners will save more than the initial cost of the cavity wall insulation within 2-4 years.
Do you need to do anything to prepare for the installation?
The installation is fairly easy, and all the work is done from outside the house. You may need to make sure there is easy access to all the walls that need to be insulated. The drilling can cause some vibrations in the walls, so it is a good idea to remove any delicate wall hung items.



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