Wall Tie Failure
The problem and causes of wall tie failure
Where insufficient or incorrect wall ties have been installed, or where failure or corrosion of the existing ties has been identified, then remedial ties will be required. Solid masonry may also delaminate through broken headers or deteriorated mortar, and require remedial tying to ensure future stability.
Helifix has developed a range of unique remedial wall tie systems to address precisely these kinds of problems.
Wall tie corrosion and failure
Wall ties may fail for any one of a number of reasons. For example, ties may fail in their connection to the substrate as a result of being excessively stiff or rigid. Where ties are too stiff, natural building movements can lead to the crushing and failure of the substrate materials that surround the tie, leaving the tie unsecured in the wall and unable to perform its structural functions.
Corrosion is another common cause of tie failure and is a widespread problem that has been well documented in Australia at least since the Newcastle earthquake in 1989.
The earthquake resulted in 13 deaths and over 150 injured. Many buildings collapsed and many lost large portions of their external cavity brick walls which were found to be unsupported, largely due to corroded galvinised wall ties. Fatalities and injuries resulted in many instances from the direct impact of falling brickwork, in others injury and death resulted from brickwork collapsing onto awnings which then collapsed under the impact of the extra weight. The event alerted building owners and professionals to the problems and risk associated with wall tie failure in cavity brick and veneer buildings.
Since 1990, codes and practices have been changed requiring the use of stainless steel and other non-corrosive materials for cavity wall ties in coastal zones where corrosion risks are greatest. However, many older buildings continue to suffer brickwork collapses during strong winds as a result of corroded wall ties.
Most cavity brick buildings in Australia built before 1990 contain wall ties made from galvanised mild steel.
Unexpected wall collapse can be extremely dangerous and require costly repairs.
Indicators of wall tie failure
The majority of corrosion of wall tie occurs within the bed joints of the external leaf. This means that the extent of the problem of wall tie corrosion and failure can be difficult to ascertain.
The most assured method of correctly diagnosing the problem is to use an endoscope or metal detector to locate and mark the position of a number of ties in each elevation, to then remove one or more bricks in the external skin and to then visually inspect the portion of the tie end embedded in the mortar joint. A range of specialist tools amd masonry saws are available to assist with the clean removal of brickwork...Read more »
Other indicators of wall tie failure include:
- Out of plumb, bowed, cracked or collapsed brickwork
- Corroded arch bars and lintels
- Rust stains in the walls
- Gaps between timber reveals and brickwork at openings
- The age and location of the building and known problems with other similar buildings in the area
