WALL TIE FAILURE
Wall ties are an important structural component ensuring the stability of the outer leaf of a cavity wall against wind loads. The condition and number of ties in the structure are important and where corrosion has set in or wall ties are missing or broken, then remedial ties will be required. Solid masonry may also delaminate through broken headers or deteriorated mortar, requiring remedial tying to ensure future stability.
Our remedial ties are used most commonly to address the problems of:
- Wall tie failure and corrosion
- Wall tie omission
- Masonry, thin panel and and render delamination
Common remedial problems
Wall tie failure and corrosion. Wall ties are an important structural component that connect the inner and outer leaves in cavity and masonry veneer wall constructions.
Structurally, wall ties are essential to the stability of the normally unloaded outer leaf which can be affected by both direct wind forces and wind suction forces. Wall ties are also often used to help outer leaf masonry resist dead loads, such as those which may be associated with the fixing of external company signage or awnings. Consequently, remedial tying will be required whenever problems involving the condition and number of ties in cavity and veneer constructions are discovered. Corrosion is one of the most common causes of wall tie failure.
Corrosion of galvanised metal cavity wall ties is a widespread problem and has been well documented in Australia 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 wall ties. Fatalities and injuries resulted in many instances from the direct impact of falling brickwork, and in others from brickwork collapsing onto awnings which then collapsed under the impact of the extra weight. The event alerted building owners and professionals to the problem of wall tie corrosion and the risks associated with wall tie failure in cavity brick buildings.
Since 1990, building 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.
Wall tie omission. Older buildings may contain only small numbers of wall ties at low density spacings which may be considered inadequate by modern standards.
The current Australian Standard for masonry structures (AS3700—2001) generally recommends that cavity and masonry veneer wall ties be spaced at not more than 600mm centres (vertical and horizontal) in unbroken masonry faces and not more than 300mm centres around openings.
Geography, building type and wind exposure classification can all influence spacing requirements and denser spacings may be required when faced with high loadings. Remedial tying will be required whenever the omission or inadequacy of the original wall tie system is discovered.
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.
Delaminated solid walls, render and thin panels. Solid masonry may delaminate through broken headers or deteriorated mortar. Similarly, thin panels and render may peel away from back-up materials as a result of a breakdown in the chemical bond. Delaminated masonry, render or thin panels may require remedial tying to ensure future stability.
Indicators of wall tie failure
The extent of problems involving wall instability and tie failure can be difficult to ascertain.
Problems associated with wall tie corrosion, for example, can be difficult to confirm since the majority of wall tie corrosion can be expected to occur within the bed joints of the external leaf.
The most assured method of correctly diagnosing the problem is to use an endoscope or metal detector to locate and mark a number of ties in each elevation, to then remove one or more bricks in the external leaf and, finally, to visually inspect the portion of the tie end embedded in the joint. A range of specialist tools amd masonry saws are available to assist with the clean removal of brickwork...Learn 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
Remedial wall tie solutions
Our high performance remedial wall ties and pinning ties have been designed to address the problems of wall tie failure and omission, and those involving masonry, thin panel and render delamination.
Our range includes:
- DryFix
Dry mechanical pinning and remedial wall tie system - RetroTie
Remedial wall tie system with dry/resin fix - ResiTie
Remedial wall tie system with resin/resin fix - CemTie
Grouted tie for stabilising solid masonry - BowTie
Wall tie system for pinning walls to floor joists - PatchPin
Concrete patching pin - StarTie
Wall starter tie system
Typically, wall type (e.g. solid, cavity or masonry veneer) and composition will dictate which particular system will be required to provide an effective wall or pinning tie solution...Learn more »