In the UK thousands of homes have problems with corrosion, and eventually the demise of wall ties for cavity walls. The most often, the root reason is the construction process that was used to construct the house and the initial installation of the wall ties . in particular , there are too few employed. We have years of knowledge and experience with a variety of property-related issues such as cavities wall tie. We take a look at the process of cavity wall tie replacements and the ways we can assist from determining the state of the wall tie to fixing damaged wall ties using our cost-effective and non-intrusive repair methods.
What exactly are Cavity Wall Ties?
Construction of cavities in brick was first introduced as a construction method in the Victorians and became widely used in the 1880’s. The two skins or leaves in brickwork (inner and outside) are anchored by the wall ties that are placed with regular spacing in both directions. Wall ties of the early days were typically specially shaped bricks. They were brittle and steel or iron tie were added. The corrosion protection offered was an oil-based coating, typically not much. Later the use of galvanised ties. The end that is buried into the mortar bed, and once it is water-resistant, then corrosion could begin. This process is made more difficult by the mortar ‘black Ash’ that is a chemically contaminated.
Cavity wall tie fail
The corrosion or rusting process of the steel or wrought iron can cause the material to expand, and to de-laminate. The expansion, if it is large enough, will make the bed of mortar break apart and raise, creating horizontal cracks that appear regularly throughout the wall. It is usually the wall facing the weather that suffers the most. In the most extreme conditions, the wall tie’s “fingers are completely corroded, and leave no connection between the inside and exterior brickwork’s skins. Wall collapse can occur when large portions of tie’s corrosion has completely stopped.
Strip ties made of steel were substituted by wire ‘butterfly’ or wire ties during the 1960’s and the 1970’s. They are corroded to nothing and don’t typically cause any lifting of the mortar bed. But they should be examined as complete failure could still happen.
A 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 determine the longevity of ties, specifically ones used for the construction of homes in the years prior to 1945. Between the years 1945 to 1964,, a relatively accurate lifespan is possible to predict:
Strip ties – They are likely to last between 31 and 61 years.
Ties to wires – The disease will is likely to last between 15 to 31 years.
You can see by the wide lifespan figures there isn’t a definitive answer to the length of time that 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 is an absolute fact is that any mild steel wall tie will at some point be affected from some kind of corrosion.
How can I tell whether my ties for the cavity wall have been damaged?
The only way to tell the property that has collapsed cavity wall ties when the wall ties actually collapsed and the erosion of the wall ties 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:
Walls that bulge outwards The joints of the wall expand, causing the wall to extend outwards. It is usually visible in the windows.
Cracks appearing on the exterior wall. Cracks visible to the naked eye will occur at regular intervals in mortar joints on the outside.
Internal wall cracks Cracks can appear inside at the wall or ceiling joint.
Cracks appear on render coats which may be visible.
Doing a Cavity Wall Tie Inspection
A preliminary inspection of the wall cavity will reveal the existence of horizontal cracks in the mortar bed at intervals usually of approximately 450mm. To determine the state of the wall tie, we find a number on every elevation with the metal detector, then drill holes near by and then examine the ties within the cavity using an endoscope.
In many cases, we can observe the severe corrosion and delamination. If there’s any doubt about the state of the wall tie, we can expose the outside by removing the mortar that surrounds it. The corrosion can be easily assessed. Sometimes, we notice that inadequate wall ties were used in construction. There should be the average 2.5 tie per sq meters. The survey of metal detectors can be used to determine the distribution. All elevations that are accessible are verified unless instructed to do so.
Replacement of Cavity Wall Ties
If the ties for the cavity wall be replaced, the procedure follows three phases:
1. The location of the wall ties to ensure that they can be placed using an offset style.
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, an appropriate colour mortar can be used as a filler for the hole.
3. Separation of old ties 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 create a new repair area.
The work is done using scaffolding or temporary towers, based on the accessibility and terrain. Wall ties made of stainless steel are employed since they are resistant to corrosion.
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