Cavity Wall Ties, Borescope Inspections & Thermal Imaging

Cavity Wall Ties, Borescope Inspections & Thermal Imaging

Boroscope and Cavity inspections

The condition of cavity wall ties may cause concern if any movement is noted to the property ie stepped cracking to the external brick or stone, cracking to internal plaster finishes or expansion of render/coated finishes.

Movement to a property can be caused by a number of reasons including subsidence due to problems with the foundations which may be caused by poor fill, excessive moisture and drying or movement due to surrounding tree roots. Otherwise from corroded cavity ties or even natural settlement. Therefore, cavity wall ties should be inspected to rule out or confirm this possible cause.

Poorly insulated cavities can also lead to major damp problems within a building including condensation leading to black spot mould and penetrating damp from cavity bridging.

Boroscope inspections allow for visual examinations within a cavity or enclosed area without the need for disruptive works involving opening up of walling or removal of fixtures and fittings. The borescope inspection is carried out by drilling a small hole of approx. 10mm to accommodate the camera fitted with a high intensity light with a reach of up to 290mm depth and 360 degree view. The borescope relays the observations to a high resolution screen to allow for viewing, photographing and recording.

Our borescope surveys are followed up with a comprehensive report, detailing the findings within a table of the drill locations, images and written summary and conclusion and will usually be accompanied by location plots.

We are also equipped to carry out surveys and inspections incorporating the use of the thermal imaging camera which helps us to further pick up on defects with insulation and leaks from enclosed pipe work.

Applications:

• Confirm wall construction, bridging and cavity voids
• Report on the presence, type and condition of Cavity Wall Insulation
• Report on the presence, type and condition of Cavity Wall Ties
• Investigate any points of potential water ingress, internal or external
• Investigate possible leaks and locate pipework
• Inspect for signs of rot or decay to inlaid timbers
• To check for infestations of rodents or insects

Key benefits of a Borescope Inspection

• Non-destructive method
• Inexpensive method
• Immediate and accurate results of viewing
• Provides photographic or video evidence from inside the inspected area.

Where render or other coatings are present it is advised that the walls are drilled internally to prevent damage to the coating.

If the cavity is filled with insulation it may not be possible to inspect the cavity wall ties without opening up the cavities, which is more disruptive and subject to higher costs.

Thermal Imaging

In order to conduct an internal thermal imaging survey, certain internal conditions are required, these should be checked off prior to the survey:

• An internal temperature of 20–22C should be maintained for at least 72 hours before inspection.
• There should be a minimum differential temperature of 10C between the internal and external temperature on the day of inspection.
• The internal surface of the external elevations should be kept clear during preparation for the survey, as above approx. 72 hours prior to the survey.
• Any external elevations with stud walling or internal cavity walls should not be included.
• All internal doors should be left open to encourage even heating of the property.
• There should be no windows or external doors left open, to avoid cold draughts and reduction in internal temperature.

External thermography inspections should not be undertaken in the following conditions.

• During wet and windy weather (above 5m/s when using an anemometer), which can overly cool the external surfaces to the extent that any anomaly will no longer be visible using thermography.
• During the day following external surfaces being exposed to heat or solar saturation from the sun.

Cavity wall insulation

Most properties built in the last 100 years have been built with two layers of wall, the outer-facing wall and an inner masonry block wall.  In-between these two walls is a cavity.  The purpose of this cavity is to prevent rainwater from seeping from the outside into the property.

In properties built in the past 20 years you would expect this cavity to have been filled with an insulator of some sort.

To reduce the amount of heat lost from a property it is recommended to have the cavity walls insulated.  Filling the cavity with a material that stops heat transfer will do this, giving you reduced heating costs.

Cavity wall insulation could reduce your heating bills so much that it will pay for itself over a short period of time.

Types of cavity wall insulation

Polystyrene Beading is the most popular choice of wall insulation.  An advantage of using this method is that the equipment used in the process has a long nozzle that shoots the beads into hard-to-reach areas.

Potential problems can occur if the beads are ‘over-bonded’ or ‘under-bonded’.  Pressure from over-bonded beads can cause cracking to the external wall allowing water to pass through to the internal wall via the hardened glue. To fix this problem you could be faced with removing the external wall of the property.

If under-bonded, insects can create nests between the beads which can cause dampness that can seep through the masonry wall.  If any alterations are made on a property with under-bonded beading cavity, that requires removing bricks, the beads will escape (like opening a thousand bean bags!) and the cavity will partially empty.

Blown Mineral Wool is made from slag rock or glass which is broken down and spun into a fibre.  It is then coated with a silicone making it water resistant.

There are potential problems with this type of insulation as whilst it is ‘water resistant’ it is not waterproof and if the property is exposed to heavy driving rain over long periods of time the chances are this water will seep into the property.

If the property is not insulated correctly when using a blown mineral wool you have the potential for large areas of the cavity not being filled sufficiently.  It is injected into the cavity under a certain pressure to ensure full coverage, but if this is not carried out by recommended/registered installers you can’t guarantee the quality of the insulation.  The cavity walls would have varying temperatures throughout the property enabling condensation/mould to form in areas not suitably filled.

Also, as with beaded insulation, insects can also nest amongst this type of insulation too.

Injected Urea Formaldehyde Foam is an insulation that many homes will have in their already insulated cavity walls, but it is no longer used.

Problems with this type of insulation are associated with the fact that when the foam comes into contact with moisture it disintegrates.  This, as like the wool insulation, will cause the cavity to have varying temperatures.

In summary, all these types of cavity wall insulation have potential problems, that can be extremely costly.  By insulating the wall and loft spaces within a property you are creating a humid box that is filled with moisture created from living and breathing, with no means of escape unless you correctly heat and ventilate your home.  If the property is not suitably heated and ventilated when the cavity walls are insulated you are highly likely to have mould growing inside cold dead air spaces, such as cupboards.

Most properties that have had cavity wall insulated by a guaranteed installer will probably have a 25 year guarantee backed by CIGA (Cavity Installers Guarantee Agency).  If within that 25 year period you require cavity wall ties replacing it could invalidate the guarantee.  If your walls have slightly recessed joints or the rendering looks like it needs painting and you have damp caused by insulation, you stand little chance of any form of compensation.

Conclusion

Cavity wall insulation in the form of a loose fill should be avoided.

So how should you insulate your property?

To avoid causing a ‘bridge’ between the outer and inner walls, thus preventing water to transfer, the following methods are recommended:

Insulated Plasterboard

This is a great way to insulate your home, if a new build/full renovation, as all walls will be filled exactly the same ensuring an even coverage and temperature throughout.

Exterior Insulated Render

If the property is already rendered, this is an ideal insulator.  Although it cannot be used on listed properties or properties within a conservation area.

Masonry Water Repellent Cream

This can be used on unpainted surfaces.  The cream will keep external bricks dry meaning the bricks will be a slightly higher temperature than that of wet bricks.  This insulator wouldn’t save you huge amounts of energy but it does help slightly.

Note:  Heating and ventilation is required in all properties to reduce the risks of humidity and mould inside.