When cavity wall ties and insulation coexist in the cavity wall of a property property, they can work well together, but if problems arise, they can also create hidden risks to the structure and stability of your home. Over time, cavity wall ties can corrode and expand, and when insulation is present, these issues are often harder to detect and can even be accelerated by the insulation in some cases. Here, we’ll explore how wall ties and insulation interact within a cavity, the potential risks to your home’s brickwork, and the signs that professional intervention may be needed.
How Wall Ties Work in Cavity Walls
Wall ties are metal connectors that secure a building’s outer and inner brickwork layers, or “leaves.” They add essential stability to the walls by bridging the cavity and ensuring the inner and outer layers of brickwork stay aligned and structurally sound. When installed correctly, wall ties should last the lifetime of a building. However, wall ties made from mild steel are particularly vulnerable to corrosion over time.
Cavity Wall Insulation and Wall Ties
Cavity wall insulation, often made of materials like EPS beads, mineral wool, or foam, fills the gap between the inner and outer walls. This insulation is intended to improve energy efficiency by reducing heat loss through the cavity. However, when cavity insulation is added to walls with mild steel wall ties, it can trap moisture against the ties, accelerating corrosion.
Once corrosion begins, the wall ties start to expand. Unlike untreated mild steel, rust occupies a larger volume, which puts pressure on the surrounding brickwork and mortar joints. This expansion eventually cracks the mortar, creating visible “step cracks” in the brickwork. Over time, the stability of the walls can be compromised, leading to a serious risk of structural damage.
The Risks of Combining Cavity Wall Ties and Insulation
The combination of cavity wall ties and insulation can lead to several problems:
Increased Corrosion Due to Trapped Moisture: Insulation materials, especially those prone to absorbing moisture (like mineral wool), can trap dampness in the cavity. This moisture can linger around wall ties, accelerating rust and expansion.
Expansion and Pressure on Brickwork: As the mild steel ties corrode and expand, they exert pressure on the brickwork, forcing it outward. This is especially problematic in older buildings where the mortar may already be weakened.
Cracking and Structural Instability: The expansion of rusting wall ties causes mortar to crack, leading to a distinctive step-cracking pattern that affects both the appearance and integrity of the walls. In severe cases, the structural integrity of the wall can be compromised, making repairs more extensive and costly.
Reduced Effectiveness of Insulation: As cracks and gaps form in the brickwork, the insulating properties of the cavity wall are reduced. Cold air can infiltrate the wall, making it less effective at retaining heat and reducing energy efficiency.
Higher Risk of Damp Penetration: Cracks in the mortar not only compromise the wall’s strength but also create pathways for water entering the cavity, leading to damp and mould problems in the building’s interior.
Identifying Signs of Wall Tie Failure and Insulation Issues
If your property has cavity wall insulation and is over 20 years old, there are several signs that wall tie failure could be an issue:
- Step Cracking
- Bulging or Bowing Walls
- Damp Patches on Internal Walls
You can read more about the sign of failing wall ties here, and the sign of failing cavity wall insulation here.
At CavClear, we specialise in wall tie surveys, wall tie replacement, and insulation extraction for properties where wall ties and insulation have began to cause issues. While cavity wall ties and insulation each play important roles in the performance of a property, the interaction between them can lead to unexpected and costly issues. If you suspect problems with your cavity wall system, such as cracking or damp, CavClear’s expert surveys and remedial services can help you identify, repair, and prevent these issues, ensuring the long-term stability of your home’s structure.
Protect your home from the risks of corroded wall ties and trapped moisture, contact us today to book a wall tie survey or consultation on cavity wall insulation extraction. Get in touch here.
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