In the UK thousands of homes have problems with corrosion, and eventually the demise of the wall ties. The most often, the root reason is the original construction of the building and the initial installation of wall ties, particularly, not enough were employed. We have years of knowledge and experience with a variety of property-related issues that include cavities wall tie replacement. We take a look at the process of cavity wall tie replacements, the wall tie inspection and the ways we can assist you in determining the state of the wall tie to replacing damaged wall ties with our non-invasive and cost-effective repair solutions.
What are Cavity Wall Ties?
The construction of brick cavities was first introduced as a method of building in the Victorians and became popular by the 1880’s. The two skins or leaves in brickwork (inner and the outer) are anchored by the wall ties that are placed in regular spacings both in both directions. The first wall ties were typically specially shaped bricks. They were brittle and steel or iron tie were added. Protection against corrosion was at best the coating of bitumen typically not much. Later the use of galvanised ties. The end that is buried into the mortar bed, and when it becomes permeable to water, the process of corrosion could begin. This process is made more difficult by the mortar ‘black Ash’ which is made up of chemical contaminants.
Cavity wall tie fail
The corrosion or rusting of the steel or wrought iron will cause it to grow and then de-laminate. If the expansion is severe enough, can result in the cement bed break apart and raise, creating horizontal cracks that show up regularly throughout the wall. It is usually the wall facing the weather that suffers the most. In the worst conditions, the wall tie’s “fingers are completely corroded, creating no direct connection between the inside and exterior brickwork’s skins. Wall collapse can occur when an overwhelming majority of tie’s corrosion has completely stopped.
The steel strip tie was replaced by wire ‘butterfly’ tie ties in the 1960’s and the 1970’s. They corrode to nothing and don’t usually result in any lifting of mortar beds. However, they must be examined as complete failure could still happen.
The most frequently asked question is: how long will the ties for cavity walls last before they have an opportunity for them to fail? Because of the nature of the ties for cavity walls, it is difficult to predict accurately the longevity of ties, specifically ones used for the construction of homes before 1945. Between the years 1945 to 1964,, a reasonably accurate life span can be anticipated:
Tie-dye ties – These are likely to last between 31 and 61 years.
Wire ties – The illness is likely to last between 15 to 31 years.
You can see by the wide lifespan figures there’s no clear answer as to how long cavity wall ties will last.
Between 1964 and the year 1981, there is a change in life span of the ties
Strip ties ranging from between 23 and 46 years
Wire ties 13 to 26
One thing that can be said for certain is that any mild steel wall tie will at some point be affected from some kind of corrosion.
What can I tell whether my ties for the cavity wall have been damaged?
The only way to determine whether a home has collapsed cavity wall ties when the wall ties have collapsed and the wear and tear of the tie have caused damage to the exterior and interior walls.
The indicators to watch out for in order to spot failure of a cavity wall are:
The wall is bulging outwards Wall joints are widened, which causes the wall to expand outwards. This can be seen in the windows.
Cracks appearing on the exterior wall. Cracks visible to the naked eye will appear on a regular basis in mortar joints on the outside.
Cracks in internal walls The cracks could appear at the ceiling and wall joints.
Cracks appear on render coats which may be there.
Conducting the Cavity Wall Tie Inspection
A preliminary inspection of the wall cavity will show the existence of horizontal cracks in the mortar bed at intervals generally of about 450mm. To determine the state of the wall tie, we find a number on every elevation with metal detectors, then make holes in the vicinity and examine the tie inside the cavity using an endoscope.
Sometimes, we see severe corrosion and delamination. If there is doubt regarding the condition of the wall tie, we can expose the outside by removing the mortar that surrounds it. The corrosion can be easily assessed. Sometimes, we discover that not enough wall ties were utilized during construction. It is recommended to have the average 2.5 tie per sq metres. The survey of metal detectors is used to verify the distribution. Every elevation accessible is examined unless we are told to do so.
Removing Cavity Wall Ties
If the ties in the cavity wall be replaced, the procedure follows three phases:
1. The location of the wall tie so that they can be placed with an offset design.
2. Installation of stainless steel mechanical (expanding) tie-ups or resin-bonded tie. A hole of 10 millimetres is made through the surface of the stone. Once the tie is put in place, the mortar of the same colour will be used for filling the holes.
3. The old ties are removed through the removal of mortar surrounding them, or using grease-filled sleeves to cover the exposed part. The sleeves or slot are then turned over to repair the area.
The work is done using scaffolding or temporary towers based on the accessibility and terrain. Steel wall ties made of stainless steel are employed since they are resistant to corrosion.
