Cladding provides protection and insulation for buildings, but the choice of materials can significantly affect fire safety. Here’s a summary of the main types of cladding used in the UK and the fire risks they may pose.
This can be a very complicated subject because, while the external-facing material may be non-combustible, there is often a significant build-up of support structure and insulation behind it that may contain combustible materials or missing cavity barriers.
If in doubt, consult a competent advisor to help assess your external wall.
1. Aluminium Cladding
Description:
Aluminium cladding is a commonly used system used on high-rise and commercial buildings due to its sleek appearance and durability. It typically consists of formed aluminium panels or sheets that are installed onto an insulated backing structure.
Risk of Combustibility:
Aluminium cladding is typically considered to be non-combustible however the actual material used needs to be considered carefully. Some aluminium cladding panels are made from ACM (Aluminium Composite Material) which consists of two thin aluminium layers surrounding a core, often made of polyethylene (PE).
The core material of ACM, if made from PE, is highly combustible and can contribute to rapid fire spread. The outer aluminium is non-combustible, but the flammable core was a key factor in the Grenfell Tower fire. Post-Grenfell regulations now restrict the use of PE cores in high-rise buildings, but many older buildings still contain ACM with combustible cores.
The backing materials should also be understood. Behind aluminium cladding there may be combustible insulation, timber sheathing boards/framing and missing cavity barriers.
2. Render and External Wall Insulation (EWI)
Description:
EWI consists of an insulating material, like expanded polystyrene (EPS) or mineral wool, applied to the exterior of buildings and covered with render. It is commonly used in refurbishment projects to improve the thermal performance of a wall.
Risk of Combustibility:
EPS is highly flammable, and if exposed to fire, it can cause flames to spread rapidly. While some EWI systems use non-combustible insulation like mineral wool, older buildings with EPS still pose significant fire risks.
3. Timber Cladding
Description:
Timber cladding is used for its natural look and feel. It is commonly used in low-rise residential buildings but also occasionally in higher-rise structures.
Risk of Combustibility:
Timber is inherently combustible. Although fire-retardant treatments can reduce the fire risk, untreated timber can easily catch fire, leading to rapid flame spread. Additionally, combustible materials used in the backing can further increase the hazard.
4. Hand-Set Brickwork or Stone
Description:
Standard hand set masonry involves using clay or concrete bricks or stone laid in mortar to form walls. It is durable, offers good thermal mass, and provides excellent weather resistance and sound insulation.
Risk of Combustibility:
Brick itself is non-combustible and provides excellent fire resistance. Hand set brick walls are generally considered lower risk, especially if there is a traditional inner leaf of brickwork or blockwork. There may however be combustible insulation and a lack of cavity barriers within the buildup.
5. Brick Slip, Stone or Terracotta Cladding
Description:
Brick slip cladding uses thin slices of brick applied to a backing board, offering the appearance of traditional brickwork with a lighter construction. Stone cladding involves applying thin pieces of natural or artificial stone to a lightweight backing structure.
Risk of Combustibility:
The brick and stone elements are non-combustible themselves. However, the backing materials and insulation used behind the cladding may be combustible. If flammable materials are used in the backing system, the fire risk is elevated, especially if cavity barriers are missing.
6. Glazing Systems
Description:
Glazing systems use glass panels in building facades, often alongside other cladding materials. They are popular in modern architecture, offering natural light and an aesthetically appealing finish.
Risk of Combustibility:
Vision glazing typically does not have to be considered, however spandrel (e.g. opaque) glazing is often used used at slab edges and party wall locations where glazing passes accoss these.
It is important to understand if combustible insulation has been used to provide insulation behind this glass, and whether fire stopping has been correctly installed to prevent the spread of fire from one compartment to another.
Conclusion
The safety of cladding systems depends on the materials used and their fire-resistance properties. Combustible materials in systems like ACM, EWI, and timber cladding pose significant fire risks.
The materials used in the External Wall should be considered within your Fire Risk Assessment, and a Fire Risk Assessment External Wall produced if there are any concerns. Typically intrusive investigations and reviews of record information will be required to assess the risk posed by the specific construction on the building to understand if it is safe and if any remedial works are required.
If you’re concerned that your building may have unsafe cladding, don’t delay in seeking professional advice. Envoy Projects are experts in remediation, offering a comprehensive service to assess, remove and replace non-compliant materials with safe, certified alternatives. With many years of experience in the construction industry, we can guide you through the process from start to finish, ensuring your building meets the latest fire safety standards.
For more information or to book a consultation, contact Envoy Projects today.
