What is a cavity Wall? And why are they Used?

Cavity Walls

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
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
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 Building Solutions 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.

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Lintels, What Have I got? Why has it failed?

Lintel construction has varied through the decades from very elaborate brick arch lintels to less elaborate concrete lintels.

Edwardian & Victorian built properties often feature very elaborate brick arch lintels and having with stood over 200 years of change many of them are showing signs of failure. One of the most common causes of brick arch lintel failure is the change of a load bearing timber window to an uPVC non load bearing window causing the common stepped cracking that apparent on many buildings.

Lintel Repair
Lintel Repair

Lintel construction has changed with various methods and materials now in use such as flat soldier course lintels, pre stressed concrete lintels and catnic lintels. They can all fail for various reasons such as changes in structural loads, ground movement, and thermal expansion, and in concrete lintels fail due to oxidisation of the reinforcing bar.

Victorian Built Lintels
Victorian Built Lintels

In the majority of cases, lintel failure can be repaired using the Twistfix heliforce system, incorporating bed joint reinforcement with pinning ties and resin injection forming masonry beams within the structure alleviating the need for costly disruptive remove and rebuild of the lintel which is the traditional approach.

Lintel Repair Using Twistfix
Lintel Repair Using Twistfix Helical Beams

Newman Building Solutions are experts in lintel repair and have installed lintel repair schemes across London and the South East.

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Bowing Walls – Lateral Restraint Ties Are The Only Option!

Help my building is bowing!

That phrase is commonly heard within the Newman Building Solutions office, being a common problem to Victorian and Edwardian built properties we are able to offer modern methods of structural repair to prevent and restrain outward movement.

Bowing walls are caused by a lack of lateral restraint, which allows the masonry panels to move independently often outwards severely weakening the structural integrity of the property.

This is often evident at the levels of the masonry where the floor joists run in accordance to the floor and ceiling joists. Tying into the floor and ceiling joists is essential in repairing and restraining the movement and traditional tie bars which are visible on many period properties are no longer required.

Newman Building Solutions utilise the Twistfix Heliforce system providing lateral restraint by inserting 1.0m, 1.5m or 2.0m ties into the floor and ceiling joists with a resin fix into the brick work providing an almost invisible repair once aesthetic brick repairs have been carried out. Incorporation lateral restraint ties with helical bar creating deep masonry beams and replacement wall ties remove the need for expensive intrusive and dangerous remove and rebuild techniques that may have been previously used.

Here is a selection of projects that this method of repair has been used to restraint outward movement.

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