Our wall tie replacement guide provides no nonsense advice on how to identify wall tie failure, the types of replacement wall tie available and how to replace the original wall ties correctly.
Whatever the cause of wall tie failure, it is important that the problem is resolved quickly and correctly to avoid serious structural damage and prevent the danger of collapse.
Do I have a cavity wall?
The first thing you need to know is if you have a cavity wall or not. Most properties from the 1930s onwards were built with cavity walls. They were designed to stop rainwater from getting into the building.
If you are unsure if you have a cavity wall, one way to tell is to look at the arrangement of bricks: if the bricks alternate between lengthways and widthways then this is a good indication that the wall is solid. If all the bricks in your wall are laid lengthways then this suggests that the property has a cavity wall.
Identifying a Solid Wall
Identifying a Cavity Wall
What are wall ties?
Cavity walls ties are unseen components that tie the internal and external leaves of a cavity wall together. They are built into the cavity wall during construction, with the ends of the ties bedded into the mortar bed at regular intervals.
The wall ties are designed to span the cavity, tying the stable inner leaf to the outer leaf in order to provide structural stability. Outer leaves tend to be high and slender, making them structurally vulnerable whereas the load-bearing inner leaf is sufficiently supported. Wall ties impart stability to the outer leaf, holding the wall in place. They are also designed to prevent water transfer from the outside and accommodate small movements in order to cope with fluctuations in temperature
Identifying Wall Tie Failure
It can be difficult to know exactly when wall ties have failed and to what extent. The most common sign of wall tie failure is the appearance of regular horizontal cracks in your outer wall. There is specialist equipment like endoscopes that can be used to inspect the condition of the wall ties within the cavity wall. There are also several external visual indications that your wall ties may have failed:
- Horizontal and sometimes vertical masonry cracking
- Bulging or bowing of brickwork
- Separation of window reveals
- Sagging or lifting lintels
If you see your outer leaf start to come away from the inner leaf then this is a tell tale sign that the wall ties have failed.
It is important to get a professional diagnosis before proceeding. You can pay for an expert to inspect the property and produce a wall tie survey to confirm the extent of the problem. Ideally a fully qualified structural engineer will be used, who has access to specialist equipment that can determine the condition of the wall ties.
A metal detector can be used to check if the cracking corresponds to the existence of a wall tie. It is a good way of locating existing wall ties and establishing the placement pattern.
You will need to install new wall ties to replace those that have failed and reinstate structural stability.
Why Do Cavity Wall Ties Fail?
Cavity wall tie failure is either down to an issue with the construction and installation of the ties or due to corrosion over time.
Cavity wall ties can fail because of a construction defect, such as the original 'built-in' cavity wall ties being omitted altogether, incorrectly spaced, incorrectly fixed or too short. Poor quality mortar may have been used, failing to provide a sufficient bond for the ties.
Wall Tie Corrosion
Historically wall ties were made from mild steel that had a galvanised layer or was painted. These coatings didn’t last, leaving the steel exposed and allowing it to corrode. According to the Property Care Association, these wall ties could corrode within 20 years of construction.
Corrosion causes mild steel wall ties to expand because the metallic oxide (rust) occupies a greater volume than the pure metal – up to several times its original thickness. The expansion caused by rusting separates the bricks above and below the bed joints in which the wall ties are laid, creating horizontal cracks and compromising the load-sharing capacity of the wall structure.
The corrosion of the wall ties or the lack of sufficient cavity wall ties in the original construction means that many properties require either further remedial wall ties to be inserted or the original cavity wall ties to be replaced. It is essential that the problem is dealt with to avoid the collapse of the outside leaf and putting yourself and others in danger.
Replacing Cavity Wall Ties
Types of Replacement Wall Ties
Here at Permagard, we stock an extensive range of replacement wall ties – also known as remedial or retrofit wall ties. Our wall ties are manufactured in 304 Stainless Steel to ensure long life protection in the future.
Different wall ties serve different purposes. For example, wall ties intended for use when constructing new walls should not be used for wall tie replacement. Here are the typical types of wall ties:
Mechanical Wall Ties
Use: Mechanical remedial wall ties use a 304 grade stainless steel rod. The rod is threaded and has special neoprene expanders on each end. It is installed by drilling 10mm holes at the specified intervals and inserting the remedial wall tie. Fixing the wall tie requires the use of a cordless drill to spin the nut on the end. As the nut tightens, it allows the bar to rotate expanding the inner and outer neoprene to grip the substrate and create the new tie between leaves.
When to use: Mechanical wall ties should only be used in properties where the brickwork is in good condition.
Products: Neoprene Mechanical Ties
Helical Wall Ties
Use: Helical wall ties are ideal for anchoring building façades, structural members and stabilising multiple width brick walls. They can be used in many different types of building materials to tie the wall leafs together. They are installed by drilling a pilot hole into the outer and inner substrate. Using the special SDS adaptor on a hammer mode only setting, you then drive the tie into the substrates. The fins of the helical tie undercut the masonry to provide an expansion-free anchorage that will withstand tension and compression loads.
When to use: Suitable for all brick and block walls regardless of condition as long as structurally sound.
Products: Permagard Easi-Fix Helical Drive Tie - this tie is made from austenitic 304 Stainless Steel and can be used as remedial wall ties to re-tie a wide range of differing materials like air-crete blocks, clay bricks, stone, concrete blocks and timber studs.
Resin Wall Ties
Use: Resin wall ties are pushed into pilot holes that have been pre-filled with resin. More resin is then pumped through the tie and fills around the end in the inner substrate wall. The resin then sets bonding it with the substrates.
When to use: Threaded Bar Resin Wall Ties can be used in almost all building materials including brick, lightweight block, timber frames and even mortar. They are ideally suited for use when the quality of the inner and outer leaf substrates are in doubt.
You also need to identify the type of bricks or blocks used in the property and select the suitable wall tie. The two main types are as follows:
Perforated Bricks - use either a resin tie in a sleeve or the helical screw wall tie.
Solid Bricks - use resin ties, mechanical ties or helical screw ties.
Do you have cavity wall insulation?
If so, you will want to avoid using chemically reactive resins as this can react with the insulation. You need to use mechanical or helical screw ties in this instance.
What length of wall tie do I need?
The first step is to find out the width of the cavity. You can do this by drilling through the outer wall and measuring the drill bit from when it touches the internal leaf then subtracting the thickness of the outer wall.
When it comes to the length of wall ties, it is recommended by the Property Care Association that: “each end of a wall tie should protrude a minimum of 50mm into each leaf wall to create a secure anchor. You will also have to take into account the centering of the tie and also tolerances. With this in mind you should be looking to allow somewhere between 65 and 75mm of embedding in each wall leaf.”
Note: The width of the cavity brick wall can vary over the length of the wall so you may want to check in different sections to ensure you get the correct wall tie length.
How to Replace Wall Ties
Replacing wall ties is a relatively easy job, providing you have the correct knowledge and equipment. Permagard stock replacement wall tie kits that are easy to use and include everything you need to replace wall ties apart from a drill.
The first step is to identify the positions of the existing cavity wall ties. You can use a metal detector for this.
Having identified the location of the existing wall ties, you can now install your replacement wall ties in positions staggered from the original cavity wall ties.
Wall Tie Spacing
It is very important to get the wall tie spacing correct to ensure structural stability. When you are replacing wall ties, 2.5 wall ties per m2 is recommended. This translates to at least one wall tie every 900mm horizontally along the brickwork and at least one tie every 450mm on the vertical.
Recommended Spacing for Replacement Wall Ties
When replacing wall ties, you want to do so in an even distribution in a staggered pattern like a diamond formation. Around openings such as windows and doors, you need to install ties at least every 300 mm vertically and 225 mm away from the opening horizontally.
Recommended Spacing for Replacement Wall Ties around an Opening
Note: Recommended spacing is for standard width bricks or blocks that are 90mm thick. If your brickwork is different then call us to discuss your options.
You should then follow the installation instructions associated with the wall tie type as detailed in the Types of Wall tie section.
Isolating Original Cavity Wall Ties
Once you have installed your remedial walls ties, you need to make sure that the original cavity wall ties are isolated to prevent further damage to the cavity wall. You can do this by fitting clan sleeves around the external end of the cavity wall tie, which will effectively isolate it. If the ties continue to corrode they can force the brickwork further apart, causing more damage. In some instances it may be necessary to remove them altogether.
Important Note: Always install the remedial ties before dealing with the old ties or removing any masonry.
Making Good and Repairs
Once all your ties have been inserted, it is good practice to make good any holes in the outer wall to prevent any possibility of water ingress into the cavity area.
Wall Tie Replacement Cost
The cost of wall tie replacement depends on a number of factors including the total wall space and the type of wall tie you use. The majority of the larger costs involved in wall tie replacement are associated with surveying the property or consulting experts.
Wall tie costs are relatively small in terms of the ties themselves. You can estimate the total cost of wall tie replacement by finding out the total wall space and the number of openings (windows, doors) you have and working it out based on 2.5 wall ties per metre squared. Many of the brick tying systems are quick and easy to use, which reduces the time the job takes and should limit labour costs.
Permagard – Cavity Wall Tie Suppliers
For further advice on cavity wall ties and wall tie replacement, contact us today. Our team are able to provide expert technical advice free of charge as well as product advice.
Property Care Association’s Code of Practice for the Installation of Remedial Wall-Ties & Lateral Restraint Ties
Designing Buildings on Wall Tie Failure
If your cracks are not down to wall tie failure you may want to consider a crack stitching kit to repair vertical and stepped cracks in your masonry wall. You can read our How To Guide: Repairing Cracks In Walls.
Blow out pump - make sure your holes are free from dust and debris with this handheld air pump.