What are cavity wall ties?

Wall ties are the unseen elements of every cavity wall. Incorporated in the walls by the construction worker when he is building the wall. They are vital to the stability and security of cavity walls. Here’s the reason.

If you see the house made from stone or brick, constructed after the start of the world war, then you are likely looking at a cavernous wall with wall ties. A wall that isn’t able to stand up straight without cavity wall ties inside.

There are two elements of the cavity wall: the leaf inside and the leaf that is external. Sometimes referred to as outer skin and inner skin brickwork. The reason wall ties are important is due to the thickness of outer skin in relation to its height the ratio between the thickness of the wall and its height is referred to as the’slenderness’. Structural engineers calculate this ratio by measuring the wall’s “radius of gyration” however, we’re not structural engineers, so we’ll make use of the rough guide which is more straightforward. ….

If the wall thickness is 110mm (the average thickness for a brick) and is one metres tall, it will have an slenderness ratio of 1:9 The wall is nine times higher than its thickness or the thickness is 9th of its height (both are the same). Thus, a typical home wall, say 5 metres high would have a slenderness ratio approximately 1:45. This is an extremely high ratio of slenderness, which implies that a wall at that height and so thin without support can be knocked over by a breeze or by a child’s hand. Consider the well-known game Jenga in which players alternate placing the wooden pieces on top one others; it becomes very difficult as the column gets larger and becomes unstable due to the rising ratio of slenderness.
This is true for every cavity wall, and that’s the reason wall ties are so vital.

What is the inside skin? It is constructed with the same material, typically brick or block work however, sometimes it is timber. It also has the same ratio of slenderness as if it was an independent of its outer skin. However, the inside skin is benefited by lots of support. This offsets the slenderness, and renders it more rigid. This includes: the floor joists and other that are anchored to the ceiling joists that can also brace it, and the roof, too, which is built upon it , and in modern houses, secured to it. These are the things that provide horizontal “lateral restraint’.

There are also the internal walls that divide the rooms. These walls are used to support the skin’s inner surface by supplying the vertical “lateral restraint.

The weight of the floors, roofs and other structures provides support to the skin. Consider this: if you constructed an uninspiring wall with a height of say, ten bricks with no mortar, and sitting on it the child would not be able to be able to push the wall down and this would provide stability. Then stand up and face the child pushes, and the wall will fall easily to comprehend.

Thus, with a cavity wall we get a solid box-like structure that has loads that provide greater stability. But, it is enclosed within a very unstable, independent structure that is able to support its self-weight and has no bracing for the lateral stability. If you were to tear off the exterior surface of a cavity wall and the structure behind it would not look attractive and damp could be able to enter, but it wouldn’t fall.

Thus, wall ties serve as the lifeline to our fragile outer skin. They are placed at regular intervals both horizontally and vertically wall ties take a portion from the stability of the home and transfer that stability to the skin of the wall. This means that the outer skin is a part of the overall structure of the wall, which reduces the slenderness of the whole wall by a mile , and then voilà, a wall that is stable and is expected to last for many decades.

Wall ties are generally made of made of metal, but plastic and composite materials are also being used. They have to be sturdy enough to hold the exterior leaf, but they also have been designed to allow a little motion, so that the leaf is able to move a little as it warms to cool and warms.

Wall Tie Corrosion is the huge remnants left behind from the years in the construction of cavity walls using mild steel wall tie. Nowadays, the material used in wall tie are stainless steel however, for a while the mild steel was utilized with either an acrylic film or zinc coating to protect. These coatings don’t last long and if wall ties start to corrode it is an issue with structural integrity and needs to be dealt with.