The History of Wall Tie installation
Cavity walls incorporating a metal wall tie have been built since the early 19th century, but it wasn’t until the 1880’s building boom that a large numbers of cavity wall dwellings were built. By 1945 a cavity wall became the normal construction method for residential dwellings and many other buildings. A Cavity Wall construction became so popular due to its ability to prevent the property suffering the affects of a damp environment.
The early metal wall ties were produced mainly from wrought or cast iron and later on mild steel was used which was either galvanised or given bitumastic treatment, this was expected to give the tie a lifespan of around sixty years, although these were still found to suffer from wall tie corrosion much earlier than expected.
In 1981 the British standard of 1945 was amended to triple the zinc coating thickness on a wire tie when the extent of the problem was recognised. It is estimated that some 10 million dwellings are affected by distress of cavity wall, attributable to wall tie failure which is not confined to just cases of poorly made ties.
Wall tie failure reported to the Building Research Establishment (BRE) includes:
- Cases of inferior bitumen
- insufficient zinc galvanising
- aggressive mortar (particularly black ash)
- exposure to marine climates (proximity to coastline)
- permeable mortar that allows rapid carbonation
Types of Wall Ties prone to failure :
- Cast iron and Wrought iron wall ties are most commonly found in a fishtail style and cause damage to the external leaf of the cavity wall by delimitation or corrosion which will usually shows as horizontal or step cracking to the external masonry. These must be removed or isolated to prevent further damage.
- Stone or slate which have a poor bond to the mortar bed and are likely to snap with natural building movement. These do not need to be removed upon Wall tie installation as they do not cause any damage once failed.
- Brick and mortar are similar to stone or slate due to the fact they are likely to snap with movement of the building but can also perish with age, these also do not need to be removed as they do not cause any damage.
- Butterfly wall ties are both heavy or light weight and only light weight wall ties in 12mm or thicker mortar joints can be left undisturbed. Heavy duty wall ties and all wall ties in mortar joints less than 12mm must be isolated or removed.
All of these listed above can be identified by one of our Surveyors who will give you an honest assessment on the condition of your cavity wall ties and how the problem can be rectified should it need it.
Get in touch with us today if you have any questions regarding wall ties or would like to book a survey. We cover a huge area along the south coast including Hampshire, Dorset, West Sussex, Guildford, London, Portsmouth, Southampton, Bournemouth, Poole, Dorchester, Chichester, Bognor Regis, Brighton, Worthing and Hove.