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What Exactly Are Wall Ties?

Wall ties are the unseen elements in the cavity walls. Incorporated inside the wall, they are inserted by the contractor when he is building the wall. They are essential to the stability and security of cavity walls. Here’s the reason.

If you are looking at the house made from stone or brick, built following the first world war, then you are likely to be looking at a cavity wall with wall ties. A wall that isn’t able to stand up straight without cavity wall ties inside.

There are two elements to the cavity wall, the leaf inside and the leaf that is external. Sometimes referred to as outer skin and inner skin brickwork. The reason that wall ties are so crucial is due to the size of the skin in relation to the height of the wall – the ratio between the wall’s thickness and its height is known as the’slenderness’. Engineers who study structural engineering calculate this by measuring the wall’s “radius of gyration” however, we’re not structural engineers and will employ the rough guide, which is more straightforward. ….

If the wall thickness is 110mm (the approximate thickness of typical brick) and is one metres tall, it will have the ratio of 1:9 for slenderness The wall is 9 times taller than its thickness or its thickness is a 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 large slenderness ratio. This implies that a wall this high and thin without support can be knocked over by a breeze or by a child’s hand. Consider the famous game Jenga in which players alternate placing the wooden pieces on top one the other. It becomes extremely tough as the column increases and becomes unstable because of the growing the slenderness ratio.
This is true for every cavity wall, and that’s why wall ties are crucial.

What about the skin? It is constructed from a similar material, typically brick or block work but occasionally timber too. It would also have the same slenderness ratio as if it was an separate from its outer skin. However, the inside skin has a lot of supports, and this offsets the slenderness, and renders it more rigid. It is comprised of the floor joists and other that are anchored to the ceiling joists that can also brace it, and the roof too, that is built on top of it and in modern houses, secured to it. These elements provide horizontal “lateral restraint’.

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

The weight of the floors, roofs and other structures can also support the skin. Imagine if you constructed an uninspiring wall that was ten bricks tall without mortar, and then sitting on it the child would not be able to move the wall because it is a load that provides stability. Then stand up and face the child pushes and the wall will fall easily to comprehend.

Thus, with a cavity wall it is a stable box-like structure that has loads that provide greater stability. However, it’s encased within a very unstable, independent structure that only is able to support its self-weight and there is no bracing to provide the lateral stability. If you took away the outer walls of a cavity and the structure behind it would not look attractive and damp could come in, but it won’t fall.

Cavity wall ties are an extra layer of protection for our fragile outer skin. They are placed at regular intervals both horizontally and vertically wall ties draw a bit of the stability of the house and transfer that stability to the exterior skin. In effect, the outer skin is a part of the total thickness of the wall. This reduces the slenderness of the whole wall by one mile. And hey voilà, a wall that is stable and will last for decades.

Wall ties are typically made of metal, however plastic and composite materials are now being utilized. They have to be sturdy enough to support the external leaf in place, however they also have been made to permit a slight motion, so that the leaf will be moved slightly when it heats down and then cools.

Wall Tie Corrosion is the huge remnants left behind from the years when cavity wall construction was done using mild steel wall tie. Today, the material used in wall tie is stainless steel however, for a while the mild steel was utilized with either an acrylic film or zinc coating to protect. The coatings are not long-lasting and when wall ties begin to corrode it is one of structural nature and needs to be dealt with.