Protective coatings provide passive fire protection and modify compartment fire dynamics for engineered wood products.
Engineered wood products are popular as lining materials and structural elements in a variety of building types, but with wood being inherently combustible, their use can pose a significant fire risk. In this Dulux webinar, Dr Greg Baker, Director of Fire Research Group Limited, details how we can use protective coatings as a form of passive fire protection in concert with performance-based design to modify compartment fire dynamics — the scientific term for how a fire burns in a room in a building — for engineered wood products and reduce fire risks.
The key information from Baker’s presentation is summarised below, or you can scroll to the bottom of this article to watch the presentation.
But first things first: let’s start with some key definitions.
What are engineered wood products?
Engineered wood products are building materials that are made by laminating layers of wood together or by binding wood fibres together into a ‘composite’ material, typically with an adhesive. Typical examples are plywood, medium density fibreboard (MDF), particleboard, cross-laminated timber (CLT), laminated veneer lumber (LVL) and glulam. “Composite” means that such materials are stronger than the cumulative strength of the individual components.
Engineered wood products are popular because they provide enhanced performance, allow for faster construction of buildings, are more durable than sawn timber, and have less impact on the environment.
What is performance-based design?
Baker’s definition of performance-based design is design that uses alternative, risk-informed methodologies to demonstrate compliance with fire safety objectives. “Alternative”, in this definition, refers to solutions where the designer is complying directly with the performance requirements and building code clauses by alternative methods, rather than using a deemed-to-satisfy solution or verification method.
Fire safety performance requirements and building code clauses in Australia and New Zealand
Australia and New Zealand have similar performance requirements and building code clauses when it comes to structural stability during a fire.
In Australia, the federal regulation Performance Requirement CP1 Structural Stability During a Fire, says that a building must have elements that maintain structural stability during the kinds of fires that are most likely to affect that building. That means engineering design must take into account things like the function of the building and its proximity to other buildings, the fire load and potential fire intensity, the presence of fire safety systems and the size of any fire compartment.
In New Zealand, Building Code Clause C6 Structural Stability requires buildings to maintain structural stability during and after the kinds of fires that are likely to affect them. This reduces the probability of occupants or fire service personnel being injured or becoming ill as a result of a fire and ensuring a low probability of damage to adjacent buildings.
The challenges of using engineered wood products in performance-based design
The challenge with using engineered wood products as either wall and ceiling lining or as structural elements in buildings is that wood is inherently combustible. Although. combustible contents in a building, such as furniture, floor coverings or plastics, pose a significant threat to building occupants in a fire, engineered wood products can also contribute to the fire.
While combustible contents pose the greater risk at the earlier stages of a fire, engineered wood products will extend the overall duration of the fire. One way that this can happen is that because engineered wood products such as CLT can be prone to delamination, depending on the type of adhesive that is used, a burnt layer of wood can fall away and expose an unburnt ”fresh” layer of wood beneath, which prolongs the fire duration.
Methods for reducing the risks of using engineered wood products in performance-based design
Bearing that in mind, there are six key ways designers can improve compartment fire dynamics and reduce the risks of using engineered wood products in performance-based design.
- Encapsulation: The most obvious option is to encapsulate the engineered wood product. Typically, this is done with sheets of paper-faced plasterboard — which makes very little contribution to a fire — that are fixed to the exposed engineered wood product surfaces and are designed to protect the wood behind for a nominated period of time.
- Partial encapsulation: It’s also possible to take a risk-based approach and strategically expose certain sections of engineered wood product and encapsulate others. Research shows that certain exposed areas contribute more to a fire than other areas; it may be possible to leave the lower half of the walls exposed, but encapsulate the upper half of the walls and the ceiling
- Fire breaks: A third variation on encapsulation is to use fire breaks to prevent a fire spreading from one exposed area of the engineered wood product to another.
- Better adhesive and mechanical fasteners: Fire-resistant glues can be used in the composite or mechanical fasteners can keep sections of burnt material attached to the unburnt sections to delay exposure of fresh fuel during a fire.
- Fire-retardant treatment: Engineered wood products can be protected from fire with the use of a fire-retardant treatment; however, such treatments need to remain durable and fit for purpose for the life of the building. In New Zealand, that’s 50 years.
- Protective coatings: Other protective coatings, such as intumescent coatings, can also prevent engineered wood products from becoming involved in a fire, even if it is for a finite period of time. A common example is to apply intumescent coatings to the exposed surface of engineered wood products that are used as internal wall and ceiling linings. Such applied coatings do need to have appropriate mechanical resistance to normal wear and tear though. When these coatings are used on structural elements, in conjunction with performance-based design, they can still achieve compliance.
Key message and where to learn more
Measures such as protective coatings and different forms of encapsulation, in conjunction with performance-based design principles, can all be used to protect structural engineered wood products so that they are more likely to maintain their structural integrity during and after building fires, protecting occupants, fire personnel and surrounding buildings. This is a useful form of risk mitigation and can help building designers meet building code performance requirements.
To learn more about how protective coatings can be used in conjunction with performance-based design to reduce fire risk, you can view the webinar below or get in touch with the Fire Research Group and Dulux Protective Coatings.
Dulux offers a range of protective coatings , including fire protection, for long-term protection against corrosion, chemical attack, graffiti defacement, abrasion and extremes of UV radiation on bridges, commercial buildings, educational and sporting facilities, manufacturing plants, mines, offshore structures, pipelines, power plants and water treatment.
The Fire Research Group is a group of highly qualified international experts in fire safety science and engineering with extensive experience in providing expert witness services, conducting specialist reviews, advising on product development and undertaking applied research on a wide range of fire safety, evacuation and risk-related topics.