While wood and wood based materials were not directly involved in the Grenfell Tower disaster, the shock waves flowing through the construction industry as a result of the tragedy will have profound effects on how all building materials are specified and used in future. Timber will be no exception. It was vital therefore that the timber sector reacted proactively to the challenges raised.
The wood protection and cladding industries have taken up that challenge in earnest, through the Wood Protection Association (WPA) and Timber Decking & Cladding Association (TDCA) respectively and, where appropriate, in partnership.
In the wake of Grenfell, the government commissioned an Independent Review of Building Regulations and Fire Safety, led by Dame Judith Hackitt, to make recommendations to ensure a robust regulatory system for the future and assurance to residents that their buildings are safe and will remain so.
The WPA made a submission to the enquiry focused on competency throughout the supply chain and a lack of effective enforcement – both major concerns for our sector.
The interim report from the Hackitt review has found that “the current regulatory system for ensuring fire safety in high-rise and complex buildings is not fit for purpose”. This applies throughout the life cycle of a building, both during construction and occupation, and is a problem connected to construction culture and regulatory effectiveness.
CTI Initiative
WPA and TDCA joined the Confederation for Timber Industries last year and are now fully engaged with the development of what may be called the “National timber fire specification”. This aims to draw all key data and product knowledge relating to the performance, design and use of timber-based materials in situations where fire is a risk.
In the critical early stages of a fire, it is the reaction to fire properties of the various materials and substrates exposed that are vital. Once a fire is more developed, then containment becomes the top priority in design. At this stage, it is the fire resistance ratings of building elements such as walls, floors and fire doors that then becomes critical. Both of these aspects will be covered by the CTI project.
Building Control Communications
WPA has also been invited by Local Authority Building Control (LABC) to form a working partnership to promote and underpin product knowledge and understanding of how best to specify and use flame retardant enhanced wood-based products. This national educational and guidance programme would be aimed primarily at Building Control policy managers and officers (BCOs) on the ground, plus specifiers and, in some instances, building contractors and householders.
LABC is keen to be supplied with digestible, relevant information, the core of which will be an interactive, online CPD-style training resource for BCOs.
The WPA team has so far submitted three technical articles for publication by LABC and has put together a detailed project communications plan and associated budget.
This draws together a project sponsor group to move forward together over the next six to nine months.
Flame retardant quality assurance
The WPA operates two complementary, independent quality schemes to verify that flame retardant-treated wood has been manufactured appropriately for its end use:
- a flame retardant formulation Product Approval Scheme;
- a treatment process quality assurance scheme called WPA Benchmark FR.
The product approval scheme involves an in-depth review of fire test data on particular flame retardant formulations by an independent panel of experts.
The WPA Benchmark FR scheme includes an independent audit and quality assurance check on companies applying these formulations or building them in at the time of panel manufacture.
The WPA has agreed to only list products and treaters that have been approved under one of these schemes.
Following Grenfell, NHBC’s building control services have become more cautious and conservative about what cladding options they will approve.
For buildings in England and Wales over 18m tall, Building Regulations Approved Document B can be complied with in one of four ways:
- by only using cladding materials of limited combustibility (Euroclass A1 or A2 substrates);
- by providing test data for the whole cladding system as it will be installed (including insulation, adhesives and fixings) in accordance with BR135/BS 8414 façade test or;
- by ensuring cladding systems are constructed from separately specified materials, with desk top assessment by a suitably qualified fire engineer;
- by providing a holistic fire engineered solution, taking into account all fire safety provisions within the building.
In NHBC’s view, results from government commissioned tests post-Grenfell provide new information on performance of tested materials in complete wall systems. This creates questions over in-service performance of untested systems.
In view of this uncertainty, they have reviewed their position and will now only accept option 1 and 2 solutions as demonstrating compliance. Unless a supplier is prepared to carry out the test work specified under option 2 (typically costing over £12,000), this effectively excludes timber from such applications, even if FR treated.
