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Fixing Insulation Boards to Walls

Last modified: 17.03.2024
Close-up of mechanical fixings being hammered into insulation boards. These washers secure EPS or mineral wool boards to the substrate before basecoat application. EWI Store offers a full range of fixings designed for stability and long-term performance in EWI systems.

When installing insulation boards on walls, ensuring they are securely fixed is crucial for enhancing energy efficiency and comfort in a building. The two primary methods for fixing insulation boards are mechanical fixings and adhesives. Each method has advantages and considerations, which we'll explore in this blog. However, it is crucial to state that both methods should be used. We strongly advise a wet and dry fix solution for many reasons. Primarily, utilising fixings and adhesive ensures that the boards are adequately secured. Fixings can fail, and adhesives can be incorrectly applied. Having a dual layer of security is, therefore, essential.

Mechanical fixings, encompassing screws, anchors, and specialised items like metal firebreak fixings, are an excellent solution for attaching insulation boards to walls. Their strength and stability ensure the insulation remains secure under various conditions. As such, they are suitable for a broad spectrum of wall types, including solid and cavity walls. Their adjustability further enhances this versatility. Should an error occur during installation, easily removing and repositioning the boards is a significant advantage. Moreover, including metal firebreak fixings adds an essential layer of fire safety, aiding in compliance with building regulations and enhancing the overall durability and strength of the insulation system against fire threats. However, the use of mechanical fixings is not without its challenges. The installation process can be more labour-intensive and time-consuming compared to adhesive methods, requiring the drilling of holes, insertion of wall plugs, and securing of screws. This raises the potential for damage to the insulation material and the underlying wall if the process is not handled carefully. Additionally, one of the most significant considerations is the risk of thermal bridging, where metal fixings can conduct heat through the insulation layer, diminishing its effectiveness. Balancing the benefits of mechanical fixings against these considerations involves careful planning, selecting appropriate materials, and mindful installation practices to minimise drawbacks while leveraging their strengths for optimal insulation performance.

Metal firebreak fixings are specific mechanical fixes designed to enhance building fire resistance. They are used with fire-resistant insulation materials to prevent the spread of flames and smoke through the insulation layer.

When using mechanical fixings, including metal firebreak fixings, it's essential to consider the following:

  • Correct Specification: Choose the right type and size of fixing for the insulation material and wall type. The specification should consider the weight of the insulation, the wall material, and the required fire resistance level.
  • Placement and Density: The placement and density of the fixings should be planned to provide an even distribution of support and to meet the fire safety requirements. This often involves consulting building codes or a structural engineer.
  • Thermal Bridging Minimisation: While metal fixings can create thermal bridges, using them judiciously and combined with other insulation strategies can minimise this effect. Options include using fixings with a lower thermal conductivity or adding an insulation layer over the fixings.

Utilising adhesive to affix insulation boards to walls represents a streamlined and efficient method that is particularly well-suited to smooth and even surfaces. This approach is especially advantageous for lightweight insulation boards, whose primary requirement is a strong, enduring bond with minimal structural impact.

  • Simplicity and Efficiency: The adhesive application process is notably straightforward, requiring fewer tools and steps than mechanical fixings. This simplicity accelerates the installation process, making it a time-efficient option for securing insulation boards.
  • Aesthetic Integrity: Adhesives leave no visible fixings, presenting a cleaner finish. This is particularly beneficial in applications where the appearance of the final installation is a consideration.
  • Thermal Performance: By eliminating the need for mechanical penetrations, adhesives help to maintain the continuous thermal envelope of the building. This reduces the risk of thermal bridging, a common issue with mechanical fixings that can compromise insulation effectiveness.
  • Surface Preparation: The effectiveness of an adhesive bond is highly dependent on the condition of the wall surface. It must be clean, dry, and stable; dust, moisture, or loose material can significantly weaken the bond.
  • Curing Time: After application, adhesives require a certain amount of time to cure fully. During this period, the insulation boards must not be disturbed, which could necessitate careful planning in project timelines.
  • Limitations on Weight and Conditions: While adhesives are suitable for many applications, their effectiveness can be limited by the weight of the insulation boards and the environmental conditions. Heavier boards or extreme temperatures may challenge the adhesive's performance. However, premium adhesives like the dual-purpose EWI-225 Premium Basecoat can attach heavier boards like Mineral Wool.

Combining mechanical fixings with adhesive to attach insulation boards to walls offers a comprehensive solution that leverages the strengths of both methods, addressing their limitations. We strongly recommend this hybrid approach for most EWI projects.

  • Enhanced Security and Stability: Mechanical fixings ensure a strong, physical anchor for the insulation boards, significantly reducing the risk of detachment under extreme conditions, such as high winds or structural shifts. This method also provides adjustability and flexibility in installation.
  • Improved Thermal Performance: By using adhesive to create a continuous bond across the insulation board, this approach minimises air gaps and reduces the potential for thermal bridging, which can occur with mechanical fixings alone. The adhesive is an additional insulation layer, contributing to a more uniform thermal envelope.
  • Aesthetic Benefits: Adhesive minimises the need for numerous mechanical fixings, resulting in fewer penetrations through the insulation system. This improves the appearance of the installed insulation. It also reduces potential points of water ingress, enhancing the durability of the wall.
  • Strategic Placement of Mechanical Fixings: It's important to carefully plan the placement of mechanical fixings to provide maximum support while minimising thermal bridging. The use of specialised insulation fixings, including those designed to minimise thermal conductivity, can be beneficial.
  • Proper Application of Adhesive: Achieving a strong, consistent bond requires thorough preparation of the wall surface, ensuring it is clean, dry, and smooth. The suitable adhesive for the specific insulation material and environmental conditions is crucial for long-term performance.
  • Balancing Both Methods: The key to successfully combining these methods is following fixing patterns. This balance should consider the insulation material, the wall's condition, and environmental exposure to ensure optimal performance and durability.