Specialist Cavity Wall Insulation Installers

Cavity wall properties have outside walls that are made up of two layers with a gap or cavity in between.

Cavity Wall Insulation (CWI) is a product that is inserted between the two layers of wall to help keep the heat in. Up to a third of household heat can be lost through the walls so insulating them is an excellent way of reducing costs and conserving heat.

Cornerstone has installed CWI in thousands of domestic properties, including private and social housing, across the UK.



If your property has uninsulated cavity walls, around one third of the heat from your home will escape through the walls. CWI is a clean, inexpensive and effective means of insulating your property and has a number of benefits:

Save up to £225 on your energy bills every year*

Reduce damp and condensation in your home

Reduce heat loss by around one third

Make your home warmer and more comfortable


Enquire about Cavity Wall Insulation today...


If your home was built after 1920 it is likely that you have cavity walls; properties built in the 1990s or later generally have insulation already installed. 

You should be able to tell which wall type you have by looking at the brickwork on the outside of your house. If your home has cavity walls, you will only be able to see the long side of the bricks like Fig A.

If your home has solid walls, you will be able to see a pattern showing the long and short side of the bricks like Fig B.

A cavity wall property will generally be suitable for CWI if the cavity is currently unfilled, at least 50mm wide and the brickwork is in a good condition.  It is not recommended for walls that are exposed to driving rain, and any issues with damp in the property should be resolved before the CWI is installed.


Cavity Wall Insulation is not a measure you can install yourself - it must be carried out by a registered installer.  They will require access to all parts of the external walls of the property.

A pre-installation survey will involve a boroscope inspection, where the surveyor will drill a small hole in the wall to check that the cavity is hollow and suitable for CWI.

Once approved, the installation process involved drilling small holes at metre intervals across the external walls of the property, through to the cavity space.  Specialised equipment is then used to ‘blow’ the insulation through these holes into the cavity.  Once the whole wall has been filled, the holes will be filled so that they are barely noticeable.

The whole process usually takes about two hours for an average sized house with good access.


Cornerstone has insulated more than 2,500 cavity wall properties to date


The cost of CWI varies between properties, from around £350 to £850, depending the on the size and condition of a property. The measure will usually pay for itself within five years.


Approximate Annual Energy Bill Savings*
Save around £225

* Figures from the Energy Saving Trust, based on insulating a gas-heated home

Approximate Annual Energy Bill Savings*
Save around £150

* Figures from the Energy Saving Trust, based on insulating a gas-heated home

Approximate Annual Energy Bill Savings*
Save around £150

*Figures from the Energy Saving Trust, based on insulating a gas-heated home

Approximate Annual Energy Bill Savings*
Save around £95

* Figures from the Energy Saving Trust, based on insulating a gas-heated home

Depending on your households circumstances, funding could be available to contribute towards the cost of CWI.  Finance options are also available.


Cavity wall insulation (CWI) is a great way to insulate your home, and if done properly on a suitable property, can make a significant difference to the thermal efficiency of a property and the energy bills of the household.  However, a number of properties that have been insulated with CWI have experienced problems, due to factors including:

  • Damage that has occurred to the insulation, such as through flooding or fire
  • Installation of the CWI in unsuitable buildings, such as timber or steel framed properties or those with porous bricks
  • Installation of CWI in buildings with high exposure to wind and rain, which can cause damp issues
  • The use of a now-banned foam that breaks down over time and drops down the cavity, and that can also release a toxic gas
  • Poor installation from rogue contractors that has left gaps in the insulation, which can also lead to damp

The good news is that failed cavity wall insulation can be easily removed, and replaced if appropriate for the property, with minimal disruption.  Cornerstone is a professional and reputable installer, and can provide expert advice in line with the more stringent technical regulations that now govern the insulation industry.


"I would just like to say how pleased we are with the work from start to finish, everyone has been very friendly and helpful – thank you."

Mrs A, Home Owner, Carlton Colville, Lowestoft

“Cornerstone have impeccably high delivery standards, they are quality driven in both their workmanship and tenant liaison and we would happily use them again on future projects."

Les Lazzell, Project Manager, South Cambridgeshire District Council

“We have a great relationship - they undertake whatever is necessary to complete the contract on time, budget and to the quality levels required. I would highly recommend Cornerstone.”

Jason MacCormick, Project Manager, Saffron Housing

Cornerstone is based in East Anglia and can generally provide services from individual installation level upwards in the following locations:

Norfolk,  Suffolk, Essex, Cambridgeshire, Peterborough, Bedfordshire, Lincolnshire, London, Kent, Sussex, Buckinghamshire, Berkshire, Nottinghamshire

However, we can deliver larger projects across the length and breadth of mainland England, from the South West to the North East.

01379 853 613
Registered Office: Cornerstone (East Anglia) Limited, Unit 2-4, Fuller Road, Harleston, Norfolk, IP20 9EA.
Registered No.05117129. Registered in England and Wales.