Protecting Timber Frame Market Growth
Urban myths surround the safety of timber buildings – especially when it comes to fire risk – and continue to overshadow proven technological advancements. It is these developments that timber frame ambassadors, and brands alike, need to make heard through the noise and rumours. Timber frame is fully compliant with all Building Regulations and proven safe in fire as demonstrated by BRE and TRADA with the Timber Frame 2000 (TF2000) project. Qualities include excellent thermal insulation properties, high structural strength and a predictable charring rate, meaning that wood in large sections in buildings can often be used unprotected.
“We still hear of some doubt cast against the use of timber frame use in the construction sector,” comments David Murray, Innovation Manager at MEDITE SMARTPLY. “One of the main concerns from end users is around liability, which can cause issues should something go wrong. According to the Structural Timber Association (STA), in a standard design tender contractor build process, the structural material specification and fire safety lies with the project architect, unless specially provided under contractor design proportion. In a project in which the design is contracted out, the responsibility for structural material choice is down to the design and build contractor who typically appoints a design manager. It is an ever-evolving topic and something that we take very seriously, especially when developing our own technologies.”
Ultimately, the issue of accountability would not be a problem if the products used were of a good enough quality. MEDITE SMARTPLY, leading manufacturers of MDF and OSB panel products, used this argument as a basis for developing a high-quality reliable OSB product that could meet the need for a flame-retardant structural material used in timber frame structures. Key to its design was its ability to fit the most demanding structural applications, such as wall sheathing, flooring and roofing, while also resisting ignition from flame and slowing down early stage fire growth in the event of arson.
The product, SMARTPLY FR OSB/3, underwent years of research and development before coming to fruition in 2014. The timing was very important as in the same year the Health and Safety Executive (HSE) wrote an open letter to the timber frame industry – in association with the STA – stating that those making design and procurement decisions that significantly affect fire risk, should consider and reduce said risk during the construction design phase.
SMARTPLY FR OSB/3 was developed to support the HSE and STA’s move to create a safer timber frame industry. It is one of the few panel products in the flame-retardant category that can be said to be truly CE certified and CPR compliant. “All FR panels that we produce from our manufacturing plants in Waterford and Clonmel, Ireland are CE certified,” adds David Murray. “Our flame-retardant OSB/3 panels are manufactured with Zeroignition® technology during production. Many other OSB and plywood panels used in the industry are post-treated, leading to visual and structural degradation and invalidation of the CE mark, even though it often remains visible.”
As a member of the Wood Protection Association (WPA) FR technical committee and previously a TRADA timber frame technical consultant, David Murray speaks with authority on the subject. “The topic of CE mark validation is a really important issue that is rarely noted or fully understood by the end consumer. It is a complex issue, but we try to make it as simple as possible for specifiers and consumers by ensuring our products are manufactured to the highest quality and fit for their intended permanent use in construction.
“There are many companies who cut corners to make their life easier or cut costs by ignoring the law, but such behaviour is reckless and illegal and can have very serious consequences for the building owner, not to mention adding to the negative myths. Products, which have a CE mark applied prior to treatment, must have a new Declaration of Performance (DoP) issued after treatment to declare the improved reaction to fire classification, but also to declare that the structural properties have not been destroyed by the pressure treatment process. This must involve sampling, testing and certification all carried out by an independent ‘Notified Body’.
“SMARTPLY FR OSB/3 is truly unique as it is manufactured and CE Marked ex-works in accordance with the harmonised standard EN 13986 to demonstrate suitability for structural use in permanent constructions, and is therefore fully compliant with the Construction Products Regulation (CPR) and EU law.”
The Wood Protection Association – the independent UK centre of excellence for wood protection technical and quality developments – has also published a document on Flame Retardant Specification and CE marking and is promoting its proper practice campaign to UK government.
Steve Young, Director at the Wood Protection Association says: “In recent years, many site-applied coatings and post-treated products have appeared in the UK with DoP, CE Mark Construction Products Regulations compliance claims and application choices that make them appear an attractive alternative to in-line FR factory production processes.
“However, it is absolutely essential that fitness for purpose is verified prior to the use of any FR treatment purporting to offer extensive fire protection performance. That’s because such products are intended to be brush or spray-applied on a building site or are superficially applied with little or no factory control. Often there is no real external verification of quality control or evidence of fire performance specific to the type, size and installation configuration of the timber elements for which long-term fire protection is required.”
The challenge faced by designers to find panel products which comply with both fire and structural requirements is a difficult one. There are many new products hitting the market that are unproven. In June 2012, a magazine article entitled ‘OSB vs MgO’ pitted both products against each other and seemed to give timber frame designers more choice. MgO panels can undoubtedly solve the issue of flame spread but there are other important design considerations that cannot be ignored, such as racking strength, moisture resistance and increased corrosion of fixings.
A paper published by the Technical University of Denmark shows that, due to the chemical composition of these panels, corrosion of fixtures and fittings is occurring in completed buildings. The damages to these fittings are reportedly caused by the fact that MgO boards that contain MgOcl2 (magnesium oxychloride cement) as a binder have poor moisture resistance and decompose over time. This is due to the absorption of moisture from the outside air especially in periods with high outdoor humidity (90-100% RH), which also causes water drops to form on surfaces. The drops contain a high amount of soluble chloride ions, which appear on the surfaces of the boards and can run down to adjacent structures spreading the issue further afield. As a result, metal fixtures fastened to, or through, the MgO and siding boards may corrode within a few years, the paper outlines.
SMARTPLY FR OSB/3 on the other hand can be fixed in the same way as standard OSB/3 using standard galvanised framing nails suitable for service class 2 conditions. David Murray says: “The FR OSB/3 product that we’ve developed is also more lightweight and easier to cut than mineral based panels. In fact, it can be installed exactly the same as standard structural OSB/3 with the added benefit of ‘built-in’ flame retardancy. It is less dusty when cut, does not crack when fixings are inserted or shatter on impact during construction, but perhaps more importantly in today’s industry climate it does not contain any added formaldehyde. Furthermore, the Zeroignition® technology is non-toxic water-based green chemistry, which contributes to an overall healthier environment and assists those that are servicing areas and industries with strict regulations concerning indoor air quality (IAQ).
“When it comes to the sustainability and traceability of our products we have an enviable guaranteed supply of FSC-certified timber sourced from our own forests in Ireland which removes the risk of illegal timber. It’s our goal to continue installing faith in the timber industry and bringing to the forefront the benefits and versatility of the product with continuous customer beneficial innovation and that includes SMARTPLY FR OSB/3.”
For more information visit: www.smartply.com/products/fr-build-osb3
