Installing Cavity Wall Ties

What are wall ties?

Wall ties, commonly referred to as brick ties, are used for buildings with cavity walls to connect the leaf’s internal and external walls, allowing both leaves to work in synchronization with each other. Though they are hidden from view after building wall ties play an vital role in ensuring the building’s stability.

The most serious structural problems can result due to insufficient or inadequate use of wall tie-ups such as cracks in masonry, dampness and, in extreme cases, it could even be the cause of collapse in the outer leaf wall. We at My Trade Products we stock the trusted and tried Ancon brand who are global leading in connecting, fixing lifting and anchoring technologies for the construction industry since 1882.

The majority of wall ties today are typically made of stainless steel because it is able to resist corrosion caused by moisture and cement without requiring any additional layer protection. They Ancon wall ties offer the longest life without maintenance and are specifically designed to keep material content to an absolute minimum. Some composite materials are also utilized, for instance, Ancon’s Teplo range of ties that are made from pultruded basalt fibers set within a resin matrix, which are suitable for ultra-low energy construction where the prevention of heat loss through ‘thermal bridge is crucial.

Installation of Wall Ties

In normal brick-to-block construction the wall ties are installed into the inside and outside leaves. The wall ties should be press-down into an area, then covered by fresh mortar. It is important to note that wall ties should never be pushed into a pre-built joint. If installing, a slight grade should be created to allow moisture to enter the cavity toward the outer leaf. The drip part of the tie must point downwards and positioned near the centre of the cavity.

If you’re building an alternative type of cavity wall like thin-joint blockwork , timber or steel frames then the wall ties will typically be put in place when the inner leaf is built and also during the construction of the outer masonry leaf.

What spacing and placement is best for wall tie?

If both leaves in the wall cavity are at least 90mm thick then it is recommended to install 2.5 wall tie-ups per m2 with a maximum horizontal spacing of 900mm, and a maximum vertical spacing of 450mm. Always check with your local Building Regulations however as this can be altered in some circumstances. The cavity wall ties should be distributed evenly across the wall area in a staggered arrangement, excluding around windows, doors roof verges, roof edges, unreturned/unbonded edges, and untied vertical movement joints. The vertical spacing of the wall ties needs to be limited to 300mm and should not exceed 225mm away from the edge the opening. This can result in the wall tie being placed on each section of blockwork that is within 225mm from openings. However, spacing may be unaffected if there is a deboned tie across the joint.

What kind of wall tie is best?

Masonry to Masonry

There are numerous factors to consider when selecting the right wall tie like the kind of masonry used, the width of the cavity and height, the number of courses/courses in the building and the geographical location.

Every aspect that influences the right usage of wall tie in any scenario are covered by a number of Eurocodes along with the Building Regulations, which should be referenced and adhered to. To complement the Building Regulations and Eurocodes, Ancon in the UK Ancon have an additional Published Document (PD 6697:2010) which helps when selecting wall ties based upon geographic and topographic factors. This means that most of the time cavities wall ties can be specified without the involvement of structural engineers.

Frame ties for Masonry and Timber

Timber frame ties are designed to allow vertical motion caused by expansion and contraction of materials with different physical properties of expansion. The wall tie must be able to deal with the variations in motion and hence it is important to select the appropriate tie for the type of movement expected in the building. Ancon’s STF6 and TIM6 tie permit 24mm frame shrinkage and fit well with most timber-framed structures up to 4 storey’s high. It is the Ancon TFMT7 is specifically designed to allow for greater movement up to 65mm, and is consequently is suitable for larger structures.

How to Identify Wall Tie Failure

It can be difficult to determine exactly when the wall tie is failing and the extent of the failure but the most common indicator is regular horizontal cracks appearing on the wall’s outer. As the wall tie rusts it will expand, causing the mortar to crack , let water in. Sometimes this rust can build over time, causing expansion that may cause distortion to the wall by bulging or bowing

Another thing to watch out for is cracks appearing in the windows masonry. When the rust begins to build up on the wall, the force creates cracks in the window reveal, which have particularly structurally vulnerable edges.

If the lintels surrounding windows and doors appear as if they’ve lifted or fallen, this could also be a signal.

If you suspect there is an issue with your wall tie Expert assistance from a surveyor is recommended. They’re equipped with special equipment and detectors to determine the degree of deuteriation of the wall tie.