Cavity Wall Insulation Frequently asked questions

Why do houses have a cavity wall?

Cavity walls were introduced to try to eliminate the damp problems associated with solid built houses. The external wall is constructed of two masonry (brick or block) walls, with a cavity (gap) of at least 50mm. Metal ties join the walls together.

How is cavity wall insulation installed?

Holes of 22mm diameter are drilled in the external wall, on the mortar joint, according to a set pattern and cavity fill injected through these holes into the cavity. After the holes are all filled a mortar mix is made up to match the existing mortar and the holes are ‘made good’.

How long will the work take?

It normally takes around two hours to install cavity wall insulation in a 3 Bed Semi House but each house is different and the job can take longer if the property is very large or if we have difficulty accessing the walls.

Is my house suitable?

We have to survey your property before we start any work, to make sure that it is suitable. This assessment may be undertaken by a Surveyor or the Technician before installation.

Is there anything that I have to do before the work starts?

When our Technicians drill your walls there is some slight vibration so it is advisable to remove ornaments from walls to avoid breakages. Also, our Technicians will need access to all of your walls e.g. inside attached garages, inside verandahs and conservatories etc. The Technician may also need to foot his ladder from your neighbours property, in which case it would be advisable to check with your neighbour that this is acceptable.

Is there much mess?

A small amount of dust is created when we drill the holes and for this reason it is advisable that you remove vehicles from the drive and any small items e.g. potted plants etc, that are close to the walls. We also advise that you close all of your windows whilst the installation is taking place and if it is a particularly windy day that you mention these points to your neighbours.

Does the Technician have to come into the house?

The Technician must undertake checks before and after installation, including any heating appliances, so it is essential that they have access to the inside of your property. Apart from these checks, all the remaining work is carried out from the outside.

My house is semi-detached, so how do you stop the material going into my neighbour’s cavity?

Our Technician will insert a bristle brush barrier down the cavity at the party wall line. This will prevent any material spreading into your neighbours walls.  If however your neighbour's house is already insulated then the cavity barrier is not needed.

Is my house suitable?

We have to survey your property before we start any work, to make sure that it is suitable. This assessment may be undertaken by a Surveyor or the Technician before installation.

Are all systems of insulation the same?

No. We use InstaFibre White Glass Wool (referred to as a mineral wool), because it is safe, very effective and simple to install, but there are other systems and materials available. Our system of Cavity Wall Insulation has been tested, assessed and approved by the British Board of Agrément (BBA) to ensure that it performs to the required standard.  Whichever system you decide upon, be sure that the Installer is properly approved and can offer a 25-year CIGA guarantee.

Are the Technicians trained?

All our cavity wall Technicians undergo training both “in house” and by CITB approved training organisations in assessing, installation, ventilation, health and safety and customer care. Our system supplier carry’s out the final checks to ensure that they are competent to install Cavity Wall Insulation. The Technician is then approved by the system designer and issued with an Approved Technician Card. Feel free to ask to see our installers’ card when they visit you.

How do I know that the walls are full?

Our system works on a diamond pattern of holes, drilled at prescribed distances from each other. Our systems BBA License confirms that drilling and filling to this pattern has been vigorously tested and will result in a complete fill. When each hole is full our machine automatically cuts out and the Technician moves on to the next hole. The Technician will also undertake checks on the machine before he starts your job to ensure that the insulation will go into the wall at the right density and he will also record the amount of material used, to ensure  that sufficient insulation has been installed.

What about the vents in my wall?

Vents which supply fresh air to fuel burning appliances must be kept open. Also underfloor vents must be kept open to ensure that your timber floors will be kept dry. Our Technician will check these vents thoroughly to ensure they are safeguarded. Any vents that are redundant and serve no useful purpose can be blocked off. The Technician will discuss these with you.

What about the finish on my walls if I have painted/rendered areas?

After a week or so when the mortared holes are dry we will return and paint over them with the closest match we can get. There is however no guarantee of a perfect match but most people are happy to wait until they next paint their walls to gat the finish they require.

Will my house be warmer?

Yes, you should find that the house stays warmer for longer – see the section “What are the Benefits of Insulating Your Home”.

How long will the insulation last?

For the life of the building – the British Board of Agrément certificate confirms this.

What should I do if I have any concerns about the work?

Contact us, we have an excellent after sales service and we will investigate your concerns thoroughly to your complete satisfaction.