Wall Ties……what are they and why do they often crop up when buying or selling a house!
Wall ties are used in the construction of cavity walls, their purpose is to tie the internal and external walls (or leafs) constructed of bricks or blocks together. Wall Ties are placed in the cavity wall during construction and span the cavity. The ends of the tie are designed to sit in the mortar beds between the brick/blockwork and form a structural bond once the cement has dried.
Wall ties come in all shapes and sizes, a common feature built into the design of the tie is means of preventing water transfer from the outer to the inner leafs. In flat ties this can be a twist. In wire ties this can be corrugations formed in the wire or again a twist.
Mild Steel Fish Tail Type Wall Tie, No Signs Of Corrision
The problem associated with wall ties is commonly referred to as Wall Tie Failure, wall ties are exposed to water and chemical attack from cement used in the construction of walls. In the north east a common type of mortar widely used in the past is referred to as black ash mortar, this type of mortar is known to have a corrosive effect on wall ties. Wall ties were traditionally made of galvanized steel, the fishtale tie being the most common. In the mid-twentieth century wire ties were widely used, again made from galvanised steel wire. As time has passed many galvanised steel ties have deteriorated due to moisture in the outer leaf of brickwork.
The corrosion may force apart the cement joints and even result in the collapse of walls if no remedial action is taken. Any cracks appearing in cavity walls dating from the twentieth century need to be investigated before irremediable damage ensues. Horizontal cracking is especially suspect. Failed ties have to be isolated and substitute specialist ties installed by drilling through inner and outer leaves from outside the building. The replacement ties may be fixed mechanically or with special adhesive resins.
Galvanised steel ties are no longer in use for this reason. For a brief period, plastic ties were used but were not satisfactory. Modern practice is to use stainless steel ties.
House Surveys & Wall Ties
Surveyors carrying out inspections in relation to house purchases will often recommend a ‘Cavity Wall Tie Survey’ is carried out prior to approving the mortgage, this is usually due to the age of the property rather than tell tale signs, surveyors tend to err on the side of caution regarding wall ties, its not uncommon for surveys to be carried out and the wall ties are fine.
We have many specialist surveying tools at our disposal when carrying out wall tie surveys to determine their condition, but the best and most trusted method is to physically remove a brick which allows you to see the part of the wall tie that is hidden as it sits in the outer leaf, its not uncommon to look inside the cavity and the exposed part of the wall tie appears fine with little or no sigs of corrosion, then when you remove the brick and expose the part of the wall tie that was embedded in the outer leaf and it has advanced stages of corrosion.
All wall tie surveys carried out by us involve the removal of bricks and a thorough inspection can then be carried out, when instructing a company to carry out a wall tie survey in the north east ask them if they provide you with photographic evidence of the wall ties, if not stay away……..we always without exception include photographs of the exposed wall ties for your peace of mind.
Call us on 0191 4159471 if you require further advice or to request a wall tie survey!