¦ Osmose is trialling its retardants on modified wood.
¦ Arch’s Dricon is BBA accredited.
¦ Wolman is launching Wolmanit Firestop in the UK.
¦ Retardant manufacturers are working with the UK Timber Frame Association to develop a new construction site safety regime.

Different timber construction applications demand different fire retardant approaches and the latter continue to develop as wood is put to wider use in the market.

The Osmose stable, for instance, includes vacuum pressure impregnated FirePRO for interior above ground applications, from joinery to cladding, sheathing and joists. The product is BS EN 13501-1:2002 compliant and claimed not to compromise timber’s “engineering qualities”, including hygroscopicity.

“We’ve also been evaluating the use of FirePRO with modified woods, which are increasingly used for cladding,” said Osmose UK general manager Gordon Ewbank. “By modifying the treatment process and chemical loadings we’ve already had good results with Thermowood and we’re now working on Accoya.”

For interior and weather-protected solid timber and sheet materials, Arch Timber Protection supplies Dricon. This is a waterborne, humidity-resistant retardant, Euroclass tested to EN 13501. It is claimed to cut smoke emission and slow flame spread and flashover.

“Dricon uniquely carries BBA accreditation which offers even greater assurance,” said Arch marketing manager Janet Sycamore. “Everything we supply comes with an independent, classification report – now a pre-requisite under new standards – to demonstrate that it has been tested with the elected timber species under the specific conditions of use.”

Like Dricon, Arch’s exterior application retardant, the polymer-based formulation NonCom can be CE-marked. It is also billed as being low corrosive, providing biological protection and having “proven stability” in fluctuating humidity.

Meanwhile, Wolman Wood Protection (BASF) is soon to launch its high-pressure impregnation product Wolmanit Firestop in the UK. It is already established across Europe and the company expects to have two Firestop treatment facilities here in the first quarter.

“A key advantage is that Firestop doesn’t require major modification to conventional high-pressure treatment plants,” said Peter Fitzsimons of Wolman. “It’s also a straightforward process to operate, with no treatment tank heating or special curing considerations. That also results in clean looking timber.”

Firestop, he added, is backed by a “full suite of performance data” and listed in the WPA‘s Fire Retardant Specification Manual.

One of the first companies to use Firestop in the UK will be WJ Timber Treatments of Hull.

“We believe there are opportunities in the UK fire retardant market and Firestop will give us the potential to tap into them,” said WJ’s managing director Mark Eggleston.”It also requires very little in terms of adapting our existing equipment and we should be ready to offer the treatment from the New Year.”

Another product, HR Prof from Fire Retardant UK, has been developed for internal or external application and, for the latter, has been put through NT 053 weathering tests by Sweden’s SP Technical Research Institute.

Fire Retardant UK has also carried out “indicative tests” on HR Prof-treated OSB 3.

“If further tests at a UK test house prove positive, formal SBi tests will be carried out to establish a classification,” said managing director Chris Dilks.

Timber frame protection

A headline issue for the timber construction sector recently has, of course, been fires in semi-completed timber frame buildings where the bare frame is still exposed. The UK Timber Frame Association is currently undertaking a major research project to tackle this issue and health and safety on building sites generally and, with treatment companies, is investigating the use of fire retardants for specific use at this point of construction.

Osmose’s product is its low-pressure impregnated Protim Frameguard. The company stresses that construction site fire safety demands a “matrix management approach”, with site security to the fore. But, it maintains, Frameguard, which is tested to BS 476 pt 7, adds a further safety element, as well as giving decay and insect protection.

“There’s little anyone can do to prevent a determined arsonist if they can access a building, but by protecting against flame spread in framing timbers, Frameguard can make starting fires more difficult and give extra time for site and emergency personnel to respond,” said Neil Ryan at Osmose-using treatment specialist PTG Timber Treatments.

Osmose has also been working to adapt Frameguard for factory spray or dip application on engineered wood products and sheet material, notably I-joists and OSB.

“We’re working closely with the UK Timber Frame Association (UKTFA) in their work to improve fire performance and site safety, which includes fire testing of products in situ in timber frame panels,” said Mr Ewbank. “We’re not saying fire retardants are the panacea, but they could provide part of the solution.”

Arch’s tailored timber frame construction site product is Vacsol FR which also promises 60-year timber preservation.

“With regard to fire treated timber frame, the UKTFA is now researching the various options available, including Vacsol FR,” said Ms Sycamore. “It is generally felt that heat release and fire propagation are the important properties to measure in this area and the single burning test method (SBi) will be used to assess performance. With regard to sheet materials [in timber frame], fire-treated plywood is also an alternative option to OSB, which is difficult to treat.”

Mr Dilks’s view is that ground floor panels in timber frame structures, where arsonists are most likely to strike, should be treated.

“This is also likely to be more palatable to the timber frame industry on cost,” he said. “However, not only should frames and studs be treated, so should the OSB sheets that give timber frame panels their structural integrity.”