Everything you need to know about wall ties
Wall ties are an incredibly important component of many houses and buildings in the United Kingdom, especially those that were constructed throughout much of the 20th century.
Up until the 1980s, galvanised wall ties were the primary type used as an
integral element of bricklaying practices in the UK. If your home was built
during this period of time, it’s more than likely that the wall ties that are
holding the bricks together are of galvanised steel or other corrosive material.
While wall ties provide structural importance, as they age, the
materials used are increasingly susceptible to corrosion and damage. Subsequently,
many wall ties have been known to corrode long before their supposed lifespan
ends. For that reason, it’s important to have your home surveyed if it was built before the 1980s, to
ensure the structural integrity of the building.
Why Are Wall Ties Important?
In the United Kingdom, buildings throughout much of the 20th century
were constructed with two different layers of bricks. An outer layer of bricks
forms the shell of the building, while an inner layer of bricks provides both
insulation and structural support. These two wall layers are spaced apart,
creating a cavity between them.
Cavity walls are a traditional method of bricklaying in the UK, but
during the 20th century these cavities began to be held together
using metal wall ties, made from various materials but predominantly iron or
steel. These wall ties provide support and stop the structures from collapsing.
In particular, they proved to be very good at protecting structures from
elemental conditions such as strong winds.
Different Types of Wall Ties
Wall ties are essentially metal bars or strips of metal that span the
cavity between the two layers of brickwork. These cavity wall ties are
generally made from steel, but the exact type of material can vary depending on
the age of the building.
Most wall ties in the UK are made from steel wire, with the older
version being fishtail shaped and newer versions being butterfly shaped. The
steel would have been treated with varying levels of galvanisation to protect
against corrosion and rust.
Wall Tie Failure
Despite being such an important component of structural stability –
without wall ties, the wall will collapse – wall ties used before the 1980s
were only designed to last for up to twenty years. In many cases, the galvanisation
process was inadequate and wall ties corroded long before this lifespan was up,
leading to dangerous structural instabilities within houses and even structural
collapses.
Predominantly, failures are caused by corrosion and rust, which occurs
over time. This is due to ineffective galvanisation and rust prevention when it
comes to the materials used. In fact, between the 1960s and 1980s, British
regulations controlling the level of required galvanisation of steel in
building materials was actually reduced. That means that homes built in this period
of the 20th century have substandard levels of protection against
rusting, making wall ties more susceptible to failure.
Rusting causes failure, because the added mass of the rust creates an
uneven distribution within the cavity, which can, in turn, cause the wall tie
itself to collapse or for weight to be shifted. This causes a dangerous effect
when multiple wall ties begin to rust and then collapse.
Rusting can be exacerbated by weather conditions and, in particular,
flooding or heavy rains can accelerate the rusting process. If walls begin to
crack, this can accelerate the process exponentially, as the inner cavities
then become further exposed to the outside elements and the rusting process
quickens.
While inadequate galvanisation is the most common reason behind wall tie
failure in the United Kingdom, there are other problems that can occur too. The
mortar that holds the bricks and wall ties in place may shift or simply be of
bad quality, while problems can also arise simply due to poor construction
techniques or bad workmanship.
How to Identify Wall Tie Failure
It’s important to identify wall tie failure in the early stages of
development, to avoid any serious and disastrous consequences.
Even with no training or little knowledge of building techniques, it’s
easy to identify major problems. However, if there are serious and obvious
symptoms of wall tie failure, you will need to act quickly to make things
structurally sound again.
The most obvious sign of wall tie failure is cracking. As wall ties begin
to rust, the distribution of weight begins to shift, which can cause bricks to
shift apart or to crack in places where the strain becomes too great. Walls may
also begin to bulge, while in the most serious cases walls may collapse
entirely.
It’s good practice to have regular wall tie surveys, even if there are no outwardly visible signs of failure, as some
problems will only be recognisable by a professional, especially if your home
was built before 1981.
Failure Prevention
Prevention is incredibly important for your safety. You can have trained
professionals such as Atlantis not only survey buildings for signs of wall tie
failure but also act to prevent catastrophic failures before it’s too late.
The prevention solutions vary depending on the extent of the corrosion
of existing wall ties. Our team will identify the problem and then provide the necessary
solutions. Dangerously corroded wall ties can be removed and replaced by more
durable wall ties, while others can be isolated, and further wall ties added to
strengthen the existing structure.
In most cases, when wall ties were placed before the 1980s it’s good
practice to work quickly to replace them with stainless steel alternatives
where possible. This increases the structural integrity of the wall itself and
ensures that you are safe from further corrosion.
Aesthetically, when wall tie replacement work is carried out, you may need to have additional work done to the outside of the building if you desire its appearance to remain uniform. In some rare cases, original brickwork patterns and looks may be disrupted, but of course this is a much better alternative to a total collapse of a cavity wall.
If you are looking for a wall tie survey, contact Atlantis Damp today. We provide comprehensive wall tie failure surveys and offer tailored solutions to keep your house structurally safe.
