Cavity walls are formed by two layers of masonry with a gap inbetween and cavity wall ties are used to help hold the inner and outer leafs of masonry in place. Cavity wall ties have been used as part of building construction to hold the inner and outer leafs of a wall together since around 1850. Without cavity wall ties, the increasing weight of masonry above would cause the two leafs to move apart. Over time corrosion and age can cause cavity wall ties to deteriorate and snap, resulting in severe structural damage to the external walls.
If corroded wall ties are left untreated, the masonry can bulge or crack and, in some cases, the building becomes unstable. It is not uncommon for entire developments to have the same problem, as all properties would be built at the same time using the same ties. It is essential to address any signs of cavity wall tie corrosion with a specialist surveyor and carry out any cavity wall tie replacement.
If you believe your property may require cavity wall tie replacement or you are concerned about the stability of your property, speak to a member of our expert team at Rentokil Property Care. Give us a call on 0800 0121 437 or complete our online contact form below and a member of our team will be in touch.
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Cavity wall ties are long strips of iron or steel (fishtail ties) that are placed into the cavity wall during construction and bridge the cavity to hold the inner and outer walls together. From the early 1920s, the twisted wire Butterfly tie started to be used.
Placed horizontally between the two walls and secured in place with mortar wall ties strengthen the wall. Their design prevents moisture running from the exterior wall to the interior wall and are essential to the safety and stability of the wall. Without wall ties or with ones which are corroded, large sections of brickwork such as gables can be affected by wind suction and face collapse.
Cavity wall ties were initially made from iron or steel, however, under damp conditions, both iron and steel corrode. To prevent deterioration, wall ties were galvanised with a protective zinc coating. Over time, the galvanised protective layer can break down, leading to wall tie failure. It was not till 1945 when the first British standard wall tie with a defined zinc coating was introduced and improved in 1981.
Cavity wall ties produced before 1981 have a history of premature failure and every year many homes across the UK suffer from cavity wall tie corrosion as a result of corrosive (black ash) mortars, permeable lime mortars, exposure to wind-driven rain, coastal locations, substandard galvanising on the tie and, on some of the early cavity wall ties, no protection from corrosion.
When fishtail wall ties corrode, they start to expand in size, forcing the outer leaf to crack along the mortar joint. Wire Butterfly ties tend to corrode and snap without expanding, so the first sign of a problem may be bulging in the wall. Most Butterfly wall ties are expected to have a design life of around 35 years but this can be much less in certain conditions. Properties built before 1981 could require cavity wall tie replacement with new wall ties. The process to replace wall ties requires specialist expertise, so it is recommended this is done by a professional.
To avoid wall tie failure in modern building construction and reduce the need to replace cavity wall ties in the future, wall ties are made from stainless steel to prevent corrosion.
Many homeowners may not spot cavity wall tie failure until the signs of cracking or bulging begin to appear. Similar damage can occur if cavity wall ties are not installed at the correct horizontal and vertical spacings or when wall ties have been left out of parts of a structure.
Horizontal Cracks - in the mortar, often at a high level, caused by the expansion of corroded wall ties on the external leaf
Bulging Brickword - caused by snapped wall ties, which can make your property unstable
Internal Cracks - internal cracks caused by the expansion of corroded wall ties are much rarer
Cracks to the render - vertical cracking to render
Lifting of roof edges - The roof load is carried by the inner leaf, but as corroded fishtail wall ties expand and crack the mortar, the outer leaf takes the load and the roof may be forced upwards, or the gable ridge rises
If you suspect your property could have a problem with cavity wall tie failure or require cavity wall tie replacement, it is essential to seek advice from a specialist surveyor. To accurately determine if cavity wall tie failure is the cause of the problem, we recommend having a cavity wall tie survey carried on your property.
During a cavity wall tie survey by one of our specialists, our surveyor will carry out a thorough survey of your property in accordance with BRE Digest 401 to establish whether there is an issue and if cavity wall tie replacement will be required.
Using diagnostic tools such as an endoscope and metal detection equipment, our experienced surveyor will identify and inspect a selection of wall ties, identify any cracks or defects to the brickwork and provide advice alongside a quote on cavity wall tie replacement.
Once we have identified your property requires cavity wall tie replacement, our surveyor will design a bespoke treatment plan to fit your needs. Our specialist technicians will treat the problem by locating and replacing corroded wall ties.
Our cavity wall tie replacement service involves;
- Drilling holes in appropriate areas of brickwork, using low impacting drills to reduce damage to the masonry.
- Install new non-corroding stainless steel wall ties at the correct density and then pull test the correct number. When installing new cavity wall ties, we use wall ties designed explicitly for existing walls. Our surveyor will discuss and recommend the best type of cavity wall ties for your property depending on the type and condition of the masonry.
- In most cases, the corroded wall ties are isolated to prevent further damage but may need to be removed.
- Drill holes are covered to match the existing wall appearance and preserve the facade of your property.
Any work required to fix bulging or cracked brickwork will be able to be carried out once the cavity wall ties have been replaced. To ensure the stability of your property, any remedial treatment to replace cavity wall ties should be conducted by a qualified specialist experienced in cavity wall tie replacement.
Upon completion, the cavity wall ties replaced are covered by our 20-year guarantee, giving you peace of mind that should a problem occur in the future you are covered. Even if you decide to sell your property we will be able to transfer your guarantee to the new owner.
If you are concerned with the stability of your property and would like expert advice on our cavity wall tie replacement service, give us a call. Our in-house property team are on hand to take your call, answer any queries you have and arrange to book you in for a cavity wall tie survey with one of our qualified surveyors.
To get in touch, give us a call on 0800 0121 437 or complete our online form below for a member of our team to get in touch.