How to Replace Corroded Wall TiesAdmin
Over time, buildings can suffer from wear and tear due to a number of reasons, including age and exposure to the elements. Wall ties, sometimes referred to as brick ties, are one of the elements of a property susceptible to such damage. Wall ties are a vital component in a building’s structure, so any wear should be spotted and dealt with effectively. The style of wall tie may vary depending on the age of the building and the masonry type, for example, masonry-to-masonry or masonry-to-timber. It’s essential to remember that the assessment and work for this type of project are carried out by an experienced structural engineer and an approved installer.
What is a Wall Tie?
Wall ties are used to connect the two cavity walls; the load-bearing inner leaf, and the protective outer leaf. Wall ties are essential for the structural integrity of a building by ensuring both leaves work together as a consistent unit. Wall tie design and material have evolved over the years. Buildings built before the 1970s tend to have ties made of galvanised steel, it was expected that these ties would last the lifetime of the building, however, after a time it was realised that these ties could begin to corrode after 15-20 years. More modern ties are made from stainless steel and are generally able to withstand corrosion during their lifetime.
Why Do Wall Ties Fail?
Wall tie failure occurs either when wall ties corrode, or they have been used or installed incorrectly. When exposed to oxygen and moisture, mild or galvanised steel can begin to rust. Rusting not only weakens the material but also causes it to expand in size. As a result, the pressure on the surrounding brickwork can cause cracking. Pressure on an external wall can also cause the wall to bulge outwards. Ties that have been improperly installed during the construction process may also result in insufficient function. When building, it is essential to ensure the correct type of tie, length and material are used, as well as the correct height and location.
How to Spot Wall Tie Failure
It can be tricky to spot if a wall tie has failed due to their concealed nature. There is, however, some tell-tale signs to look out for.
· Cracked brickwork, usually horizontal or stepped
· Bulging walls
· Rust staining on brickwork
· Sagging or lifting lintels
Specialist equipment such as endoscopes may be needed to inspect the condition of the ties. A qualified structural engineer can carry out a professional wall tie survey to assess the extent of the issue. If wall ties have failed, it is necessary to replace them in order to reinstate structural stability.
Replacing Corroded Wall Ties
The solution for replacing ties involves the installation of remedial wall ties, along with the isolation or removal of the existing wall ties. There are a variety of remedial wall ties available, but there are three that are most commonly used:
Mechanical expander replacement wall ties – consisting of a threaded rod with neoprene expanders on each end. Pushed through predrilled holes, a drill is used to spin the nut at the end, as the nut tightens the sleeves expand. Must only be used where brickwork is in good condition.
Resin replacement wall ties – the ties are placed into holes followed by resin or grout which then sets. Not suitable to be used where cavity wall insulation is present.
Helical replacement wall ties – usually suitable for most jobs as their shape allows for expansion free anchorage without the use of resin.
Martin Perry Associates are qualified structural engineers and chartered surveyors in Cornwall and the West Country. We provide a wide range of property services including structural reports, house surveys and structural design for extensions, loft conversions and new builds. Visit our website or contact us for additional information, or browse our blog for more details on structural inspections.