The devil is in the detail: fire protection processes for timber

Howard Morris at Trade Fabrication Systems explores the relative performance benefits of fire-retardant surface coatings and pressure treatments for timber, and explains the merits of an alternative process

Admired for its rustic appearance, strength and cost, timber is an attractive material for use within construction, but it has a major flaw – it burns. As fire protection drives design, it is integral for architects to utilise products and solutions that meet the needs of the market, while guaranteeing adherence to Building Regulations.

The Euro Class system determines a product’s fire performance by measuring it against a comprehensive set of characteristics. As wood is an organic combustible material, it will never achieve Euro Class A1 or A2 non-combustibility. With this in mind, the highest fire-retardant classification wood can receive is Euro Class B which can be successfully achieved by embracing timber technologies and enhancing the substrate. There are two main types of fire-retardant timber treatment that can be used to achieve compliance; pressurised treatment and surface coating.

Scratching the surface of FR coatings
One of the most common forms of fire protection for timber substrates is the application of fire retardant coatings. Cost effective and compliant, the coating can be applied to any wood-based product through a traditional onsite coating process. Protecting the appearance of the substrate, while also guaranteeing its structural integrity remains intact, surface coating is an ideal way to ensure timber complies with Euro Class specification.

However, true compliance is entirely dependent on the coating applied and the timber substrate originally tested. For example, if the type of timber used differs to the one that was tested, this solution will be non compliant – as the fire retardant coating may not perform as expected in practice. The same is also true if the coating is not applied to the exact specification and consistency of that tested. So, while fire retardant coatings represent a cost effective route to delivering fire protection performance, there remains room for error onsite, particularly in relation to the quality control of workmanship.

Under pressure to perform
Pressure treatment is an alternative method to Building Regulations compliance. A time consuming process, the timber substrate is impregnated with chemical preservatives to enhance its durability and withstand damage and exposure to the elements.

The pressure treatment method should guarantee compliance to Euro Class B as it is completed under factory-controlled conditions. However, due to the extensive impregnation process, the structural integrity of the board is compromised, leading to the quality of the board in installation deteriorating. While the substrate will be fire retardant, the structural integrity is brought into question.

The devil is in the detail
Both methods of enhancing a timber substrate to achieve fire retardance are achievable, but it is important to recognise the market challenge of these traditional methods. Coating onsite and pressure treatments are not without risk of compromise or challenge. As the devil is in the detail, without factory assured processes it is impossible to guarantee the fire retardant performance as well as structural integrity of the board.

Advances in offsite processing potential and timber technologies have addressed these issues head on. Factory applying fire retardant coating instils confidence in the performance of the coating, ensuring that it has been applied correctly and to the right specification consistently – without impacting its structure. This additionally ensures the specification will be protected, as the product will be delivered to site fully finished and ready for installation, which reduces the risk of the substrate being changed onsite.

In order to achieve full compliance to Euro Class B, embracing offsite processes that guarantee performance is the safest way to adhere to Building Regulations. Working with a partner who has achieved ISO 9001 quality assurance accreditation, independent certification and receives regular factory audits is the only way to guarantee overall compliance and safeguard the internal environment.

Howard Morris is managing director at Trade Fabrication Systems