What are wall ties?
Wall ties, which are often referred as brick ties, are used in buildings that have cavity walls to link the internal and external leaf walls, allowing both leaves to work in sync with each other. While they’re hidden from sight after construction, wall ties play a vital role in ensuring the building’s stability.
Serious structural issues can arise from the improper or insufficient usage of cavity wall ties such as masonry cracks, dampness and in some cases maybe even the collapse of an leaf wall. Here at My Trade Products we stock the trusted and tried Ancon brand who are global experts in fixing, connecting, lifting and anchoring techniques for construction since 1882.
The majority of wall ties today are mostly made of stainless steel, as it is able to withstand corrosion caused by moisture and cement without the need for additional layer protection. They Ancon wall ties provide an unmaintained life span and are specifically engineered for keeping the material’s content to the minimum. A variety of composite materials are employed, like Ancon’s Teplo range of ties which are made from pultruded basalt fibers that are set in a resin matrix, which are perfect for ultra-low-energy construction where the reduction of heat loss through ‘thermal bridge is particularly crucial.
Installing Wall Ties
In normal brick-to-block construction, the wall tie is built into the inner and outside leaves. The wall ties must be pressed down in the mortar, then covered with fresh mortar. Please note, wall ties should not be pushed into an existing joint. If installing, the slightest slope must be made to allow the moisture to enter the cavity toward the leaf’s outer edge. The drip end of the tie should be pointing downwards and positioned near the centre of the cavity.
If you are building a different kind of cavity wall, like thin-joint blockwork , timber or steel frames then the wall ties will typically be put in place after the inner leaf is put up and before the construction of the outer leaf.
What spacing and positioning do you need to use for wall tie?
If both leaves on the exterior wall of the building are at least 90mm thick then it’s suggested to use 2.5 walls ties for each m2 using a maximum horizontal spacing of 900mm and a maximum vertical spacing of 500mm. Always check with the Building Regulations however as this could be different in certain instances. Divide the wall ties equally across the wall area in a staggered arrangement, excluding around openings such as windows, doors and roof verges. Also, do not return or bond edges and un-tied vertical movement joints where the vertical spacing of the wall ties must be limited to 300mm and should not exceed 225mm from the edge of the opening. This can result in a wall tie on every section of blockwork that is within 225mm of openings. The spacing can be relaxed if the joint has a deboned tie spanning it.
What kind of tie should you choose?
Masonry to Masonry
There are many factors to take into account for choosing the best wall tie for the job like the type of masonry used, the width of the cavity the number of courses/heights of building and the geographical location.
Every aspect that influences the right usage of wall tie within a particular circumstance are covered under a range of Eurocodes along with the Building Regulations, which should be referred and adhered to. To supplement those Building Regulations and Eurocodes, Ancon in the UK Ancon are also governed by a published document (PD 6697:2010) that aids when selecting wall ties on the basis of topographic and geographic factors. This means that, in the majority of cases, cavity wall ties may be specified without the involvement of a structural engineer.
The Masonry to Timber frame tie
The timber frame tie is designed to allow vertical movement that is caused by the expanding and shrinking of the materials with different thermo-expansion properties. The wall tie has to be flexible enough to cope with the difference in movement and , therefore, it is vital to choose the right tie for the type of construction’s movement. Ancon ties STF6 and TIM6 allow for 24mm frame shrinkage and are suitable for the majority of timber framed buildings up to four storeys in height. Ancon TFMT7 Ancon TFMT7 is specifically designed to allow for greater movement of up to 65mm . It is consequently is suitable for larger structures.
Identifying Wall Tie Failure
It is difficult to know precisely when a wall tie has failed and what the cause of the failing, but the most typical sign is regular horizontal cracks appearing in the outer wall. As the wall tie rusts it expands, causing the mortar to break and allowing water to seep in. Sometimes, this rust may build over time, causing expansion that may cause distortion to the wall due to bulging or bowing.
Another indication to look for is cracking in the wall of the window. As the rust builds on the wall, it up and cracks appear on the window reveal, which are especially vulnerable to structural damage.
If the lintels surrounding windows and doors look like they’ve lifted or fallen, this could be another signal.
If it’s suspected that you’re experiencing a wall tie failure, professional help from a surveyor is recommended. They’re equipped with special devices and detectors to detect the degree of destruction of your wall tie.
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