The external wall of a house is constructed of two masonry (brick or block) walls, with a cavity (gap) of at least 50mm between. Metal ties join the two walls together.

The cavity wall is injected with insulating material by drilling holes in the external wall, approx. 1.5m apart, through the mortar joint. Holes are generally of 22-25mm diameter and are 'made good' after injection. Each hole is injected in turn, starting at the bottom.

Cavity wall insulation normally takes around two hours to install, but the time does depend on the size of the house and other factors, such as access.

Before the installation, Miller Pattison Ltd will undertake an assessment of your property to confirm that it is suitable for insulation. This assessment may be undertaken by a surveyor or the Technician before installation.

The drilling process does create some vibration, it would be wise to remove ornaments from external walls and window ledges, for their safety and your peace of mind. If possible keep pets indoors before installation.

The technician will need access to all walls, so he will need to get inside attached garages, lean-to sheds, conservatories etc. The insulation can only be really effective if all walls are done. If you have a wall right on the boundary, you may like to mention to your neighbour that the Technician will need to go onto their property and it is sensible to obtain their permission before we start work.

The drilling process inevitably creates a little dust, which will be cleared at the completion of the job. It may be wise to remove vehicles from the drive and things close to the walls. This will also give the Technician better access for equipment and tools. Remember to warn the neighbours and ask them to keep their windows closed during the process. Take washing in!

The Technician must undertake checks before and after installation, including any heating appliances, so it is essential that they have access to the property.

Assuming your neighbour's house is not already insulated, the Technician will insert a cavity barrier at the party wall line. This is usually a length of bristle brush which goes inside the cavity and will not be visible. Of course, if the neighbour's house were to be insulated at the same time, the cavity barrier would not be needed.

There are several different types of insulation: -
      • Bonded Beads (white polystyrene beads);
      • Glass Wool (yellow or white in colour);
      • Rock Wool (grey/brown in colour);
      • Urea Formaldehyde Foam (white foam);
Note: both Glass Wool and Rock Wool are known as 'Mineral Wool'.
All systems of CWI have been tested, assessed and approved by the British Board of Agrément or the British Standards Institution. All are suitable for their purpose.
Except for Urea Formaldehyde Foam, the systems can be used in all parts of the UK.
All systems have a similar insulation value.

All Technicians (team leaders) undergo training by the system supplier and the installing firm to ensure they are competent in CWI and carry a training card. Please feel free to ask to see the training card.