Tower block construction began in the 1950’s with the first tower block in Britain being built, The Lawn in Harlow, Essex. The need for housing influenced the decision for tower block construction and it boomed.
The Lawn, Essex
Tower blocks are constructed usually using three methods; in-situ, Steel frame with infill panel and pre-fabricated panels. In theory all three methods of construction should have provided structures free from structural defect and with stand the test of time. In reality many high rise structures are in urgent need of refurbishment to ensure they do not enter a state of disrepair with the only solution being demolition.
With all three methods of construction there are common structural defects found that are often similar across the country. Cracking is usually evident within the external and internal fabric of the structure and the defects are often linked to one or more of these causes of movement, thermal movement, lack of movement joints and failed wall ties or inadequate wall ties. Poor construction methods during the build phase. Concrete failure as well is a common structural defect found which can be caused by many factors such as oxidisation of the reinforcing steel, the reinforcing steel being too close to the surface of the concrete which again causes oxidisation freeze thaw action and chemical reaction to name but a few.
Trellick Tower, West London
Newman’s are approved designers and installers of the Twistfix and Thor Helical repair systems combined with our experience we provide our own specifications for wall tie replacement schemes as well as crack stitching and masonry beams. We are also approved installers for Fosroc and Sika concrete repair mortars and resins, mastic and coatings.
When assessing the requirements for repair to tower blocks you should only use an experienced contractor and Newman’s surveyors and engineers have extensive experience carrying out structural surveys and designing structural repair programmes to reinstate the structural integrity to tower blocks. We have worked closely with many principal contractors and façade installation specialists to provide insurance backed repair schemes prolonging the life of the tower block.
We can also provide rope access surveys and installation on schemes that it isn’t feasible to supply and erect traditional access methods such as tube and clip scaffolding or cradle access.
At Newman’s we carry out a large volume of wall tie surveys across London and the South coast to properties that have had a wall tie failure of the original wall ties, but ever increasingly we are receiving more and more inquiries for wall tie surveys after new remedial wall ties have been installed, and failed.
There are many different wall ties available on the market to diy’ers and untrained installers who see the installation as simple as drilling a hole, tightening an expander or using a resin or mastic to fix the wall tie.
In principal installation is simple, specification of an appropriate tie is also fairly simple, but to do it correctly and install a lasting permanent solution isn’t if you are not experienced.
for instance here is a tie installed by a ‘reputable’ cavity wall insulation company who decided they would install wall ties to 9 retirement bungalows…..
Failed Wall Tie
The wall tie has smashed the brick in half losing all bearing within the brick and it was found to be fixed with a red flexible caulk type mastic. This is a prime example of remedial wall tie installation carried out by untrained persons who unfortunately have failed to restore the structural integrity.
Wall ties are a vital part of your structure and should only be installed by experienced contractors.
A cavity wall is a fairly modern method of construction used when constructing buildings, it give a gap between the two skins of masonry. The construction of cavity walls began in the late 20th century to prevent the penetration of moisture through the outer skin of the building into the inner leaf of the wall. During early construction of cavity walls the masonry panels were tied using bricks placed end on into the inner skin until a metal wall tie was developed.
Cavity Wall Construction
The Introduction of the Iron Fishtail.
Cavity construction had begun in the early 1900’s but with a huge house building boom in Britain in the 1930’s cavity wall construction was the main method adopted due to the speed and ease of construction and this new method prevented damp penetration between the two skins. Wrought and cast iron ‘fishtail ties’ were developed and rapidly deployed as a structural component tying the two skins together.
Corroded Fishtail Wall Tie
The Problem.
Wrought and Cast Iron are prone to corrosion, this causes them to fail weakening the structure and putting the property at risk of collapse. The fishtail ties corrode and there are many factors that cause the corrosion mainly being oxidisation of the iron causing expansion of the tie which lifts the bed joint it is bedded in causing horizontal cracking and loss of strength allowing lateral movement. Other factors such as aggressive mortar like those found in black ash mortar accelerate corrosion as well as the porous and weak Lime sand mortar often used in London. The problem is rapidly accelerated in coastal areas found across the South East coast due to the high content of salt water present. As well as corrosion tie density and spacing is also a cause of concern as it is often found that there are inadequate wall ties within the masonry panel especially at the weakest points around window and door openings.
Wall Tie Installation
The Solution.
Help is at hand with the specialist Twistfix CD Remedial Wall tie, of which Newman’s are approved designers and installers of this type of repair specification. A specialist remedial wall tie programme will be designed by our team of surveyors and engineers who carry out a site investigation and will determine the appropriate course of action offering a cost effective repair solution. The existing failed wall ties are covered with a specialist designed sleeve that encompasses the corroded tie in a resin preventing further corrosion. Remedial ties are installed across the effective areas conforming to the latest British Standards restoring the structural integrity of the property and tying the two skins of masonry together.
