Timber protection specialists Arch explain the ‘what and why’, for fire retardant treatment for timbers used in construction.
If you are involved in the specification of building materials and you have chosen wood as part of the, overall project - congratulations! An admirable choice for our most versatile, aesthetically pleasing, and environmentally advanced construction product.
Just consider some of wood’s key attributes and benefits.
• Wood has a natural warmth and beauty.
• Wood has a natural built-in strength yet can be easily worked and, shaped.
• Wood products act as a carbon sink throughout their life, reducing, the CO2 in the atmosphere.
• Wood has the lowest energy consumption and the lowest CO2, emission of any commonly used building material.
• Wood’s thermal insulation properties mean timber frame houses, use less energy.
• Wood is uniquely renewable and its future is cared for with, responsible forest management schemes.
• Using wood products encourages forestry to expand, increasing, the carbon sink effect.
However, in common with the Building Regulatory Authorities and, insurance company loss adjusters, you may have a concern about its, behaviour in a fire; after all wood has served as a fuel throughout the, history of mankind.
Proven protection
Don’t worry! Correct design specification and the correct use of, modern fire retardant treatments can help to ensure that wood is a, long lasting and safe choice of material. Also, wood in itself has, excellent properties that help it to perform well in a fire situation, over alternative building materials. It has a steady charring rate, low, heat conduction and does not distort at high temperatures. Fire, fighters prefer to enter a burning building made out of timber, because they have learned to estimate how long they can safely, remain in the structure. In a fire wood carbonises from the outside in, leaving a core of structurally strong timber. That is why it is, predictable - unlike masonry which cracks and spalls or steel, which, buckles and twists.
Furthermore, the pressure treatment of timber with industrially, applied fire retardant formulations delays and can even prevent, ignition and spread of flame and reduces the rate of heat release. These factors help maintain the integrity of structures, enabling both, compliance to Building Regulations in terms of escape and safety of, life and restricting damage to the building fabric itself, to avoid huge, insurance losses. A prime example was a recent project undertaken, by Scarborough Borough Council - see panel opposite.
Which treatment should you specify?
Fire retardant treatments can be applied to timber and wood based, substrates in a variety of ways. For instance, by vacuum pressure, impregnation of new build timber components and plywood and also, with in-situ brushing or spraying of coatings. For the specifier, the, overwhelming consideration in making this choice is COMPLIANCE.
With a duty of care to make sure that the fire protection that is, specified will be reliable and fit for purpose in these safety critical, end uses, there are 3 main aspects in ensuring a suitable compliance, and achieving peace of mind - product application, product, certification and product performance.
Product Application
If fire retardant treatments are to be made to new timbers going into, a building then by far the most effective are pressure pre-treatments., Whilst flame retardant coatings can be very effective, their, application and their maintenance can be open to variation and even, misuse. Fire performance can only be assured when the application, is carried out under an independent certification and accreditation, scheme. Generally, coating products are not used this way and they, should be used only to upgrade timbers that are already in situ within, a building - in refurbishment, repair and improvement projects.
With pressure pre-treatments both solid timbers and board, materials can be given a measured, controlled, highly effective and, permanent protection that is applied to all faces of the timber and, will require no maintenance.
Fire has the highest level of attestation in European standards and a, supplier of fire retardant pressure pre-treated timbers must have an, independently audited factory production control system in place, in, accordance with ISO 9001, the international standard for quality, management systems. Also, for a supplier to be listed in the UK, Wood Protection Association quality scheme for fire retardant, treatments suppliers again require ISO 9001 accreditation. Arch, Timber Protection has both ISO 9001 and ISO 14001 (international standard for environmental management systems) accreditation for, its fire retardant treatment facility.
Product Certification
With regard to certification against relevant standards, currently there is a transitional stage between traditional British Standards, and new European classifications. Eventually, over the next few, years, the European classifications, referred to as Euroclasses, will, become mandatory for materials used for permanent constructions.
To support a Euroclass performance, classification reports from a, notified body according to BS EN 13501-1 are a definite requirement., Simple fire test reports are insufficient. The description of the, product given in the classification report has to be comparable with, the specification of the timber components to be used in the project.
For example, if a classification report refers to Euroclass B, s1, d0, being achieved on 25mm thick spruce boards tested without an air, gap on plasterboard, then the product cannot be assumed to confer, the same reaction-to-fire performance for:
• Timbers less than 25mm
• Alternative species
• With an air gap
• Other backing materials deemed to be of higher risk
The priority is to check with your supplier if they have a relevant, classification report to match your particular requirement. Arch has, invested in classification reports to match a wide range of species, sizes and end uses.
Product Performance
Finally, when specifying you need to be assured that the fire, retardant performance of the treated timbers will last. Here, compliance with the draft European standard on durability is a must -, prEn 15912 highlights the durability classes of reaction to fire, performance of fire-retardant wood-based products in both interior, and exterior end use applications. Meeting this classification will not, only ensure that a product is fit for purpose but will also prevent, staining, decay, poor paint adhesion, migration and exuding of, chemicals, moisture at the high humidities and corrosion of metal, fasteners.
Both DRICON and NON-COM Exterior treated timbers meet this, important standard. Also results of an independent 21 year exposure, study with DRICON fire retardant treated timber have recently been, published and they confirm that the initial fire performance, characteristics of the timbers have been maintained over this period. These results are very positive and demonstrate that the fire, retardant treatment will still be protecting projects such as, Scarborough's pagoda to the same standard for at least another two, decades.
The ultimate peace of mind for such an important specification has to, be third party quality assurance and using products and suppliers, with a proven track record. Both DRICON and NON-COM Exterior fire, retardants from Arch have over 25 years of proven commercial use, around the world and DRICON treatment remains the only BBA, Certified fire retardant treatment for timber available today.
