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Cavity wall ties

Cavity walls have been a common feature of buildings in the UK for over one hundred years. Two leaves of brick or stonework are held together using metal straps or “wall ties”. The cavities between the two leaves of masonry/brick provide an effective barrier to water penetration and also acts as an insulation layer.

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When problems occur with cavity wall ties

In some circumstances these wall ties can corrode or fail. Failure can manifest itself as cracking in the external leaf of masonry, structural movement or in severe cases the collapse of sections of masonry.

Earlier cavity wall ties were usually made from mild steel. When exposed to moisture, this can lead to corrosion and expansion resulting in inadequate support for the outer masonry/brick leave. This ultimately will result in structural failure i.e. the outer leaf of the wall collapsing. 

However, it is worth pointing out that corrosion to more modern style ties (such as lightweight butterfly or wire ties) can produce almost no detectable external symptoms. Therefore, the tie can corrode to the point of failure without ever becoming apparent externally.

Cavity wall tie failure - PCA

Other factors leading to problems

As the results of defective wall ties became better understood in the late 1980s early 1990s, a rush was seen to facilitate the demand. In many instances work was undertaken by contractors with little understanding of the wall stabilisation, or with any regard to the quality of their work. Sadly for many homeowners, has resulted in a legacy of poor and inadequate work that continues to require addressing and correcting.

Indicators of possible wall tie failure

Often the first indicator of wall tie corrosion is horizontal cracking along mortar joints externally. In more severe cases, this can also be mirrored on internal plaster. Other indicators of a potential failure include:

  • Bowing or undulating walls
  • Possible gaps developing around windows frames as joints widen (due to bowing)
  • Possible lifting of roof edges at gables
  • Internal cracks – vertical cracks may be found at internal wall junctions & horizontal cracks appear at internal wall & ceiling joints
  • Cracks to render coats

What you can do

By taking early action and diagnosing the issue early, the correct remedial action can be taken to prevent structural failure. This normally takes the form of installing modern style steel wall ties, and if appropriate removing the existing ties.

A specialist contractor can install remedial wall ties to re-anchor the two leaves of the cavity wall. Remedial wall ties come in a variety of forms, but generally fall into three main groups, mechanical, resin, and driven. 
Upon completion of this work, a competent contractor that specialises in structural repairs should provide a long term guarantee for your peace of mind. 

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Where you can find a competent wall tie contractor

Members of the PCA that specialise in structural repair are the recommended first port of call for practical advice on structural maintenance. The ability to implement necessary and appropriate remedial treatments has saved huge sums of money that would have otherwise been spent rebuilding structures.

Members who specialise in structural repair are proficient in a number of techniques that can be utilised to repair or restrain masonry walls. PCA contractors will also be able to undertake inspections and provide corrective measures where existing cavity wall ties have failed, become corroded or are in need of replacement.

The PCA’s nationwide list of contractor members are carefully vetted before being awarded membership and are then subjected to rigorous ongoing auditing procedures once admitted to the association. Members of the PCA can offer insurance backed guarantees for much of the structural work they undertake. 

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Because of the high standards of service and quality that is expected from PCA members, all PCA contractor members have Government's TrustMark accreditation.

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