Is your fire retardant protected timber fit for purpose?

The failure of fire retardant treatments to perform when a blaze breaks out could see the companies and individuals involved in the design and construction of the building brought before the courts. Jacqui Hughes, fire retardants manager at Lonza Wood Protection, outlines how to ensure that your fire retardant protected timbers are fully compliant

Fire retardant (FR) treatments for any construction material are designed to do a very important job. Should a fire situation arise in a building the protected materials will slow down combustion and limit the spread of flame and generation of smoke. They provide peace of mind for specifiers and designers by giving extra time to evacuate buildings, limit potential damage but, most importantly, they help save lives.

Any death caused in a building fire is a tragedy for those linked to the victim or victims. However, due to modern legislation such as the Construction (Design and Management) Regulations 2007 the ramifications can have severe consequences for any company or designer associated with the design and build of the project.

A court of law will want to know how fire protection systems were selected and whether there was adequate liaison between all the parties involved in making sure that the protection was appropriate. So how can you be sure that your fire retardant protected timbers are fully compliant?

Fire protection due diligence

Failure to perform when required carries serious consequences. So it is important to carry out some simple due diligence to make sure that you can demonstrate that you made the correct decision. Firstly, ensure that any FR treatments from your suppliers have independent, species specific Classification Reports.

Fire retardant treatments for timbers to be used in permanent construction must now meet the requirements of either Euroclass B or C of the European Standard EN 13501-1 to comply with both national Building Standards and the Construction Products Regulation. These requirements call for species specific testing yet some fire retardant treatments are being promoted using non-species specific reports.

The fire performance of wood and wood based panels is highly species specific, with different species requiring different chemical retentions to derive the same level of fire protection. Classification Reports supplied by treatment companies therefore must be species specific and reports that include generic terms such as ‘softwood’ and ‘plywood’ should be seriously questioned.

Industry Reference Bodies

A key step for any specification of fire retardant treated timbers should be a reference to the UK Wood Protection Association ( check list which gives general guidance and listings of approved products and quality treatment companies.

Then ensure these companies have independent and species specific Classification Reports, relevant to the timbers you are using and where and how they will be used. These should cover four particular requirements: the timber species; the thickness of the timber; whether there will be an air gap behind the timber; and the nature of any backing materials. It is a duty of care for both specifiers and building control officers to demand this proof from the treatment supplier.

Other key factors to consider in the specification of fire retardant treated timbers are product performance and assurance; quality of application; durability and maintenance; and availability and cost.

Performance and Assurance

Industrially applied FR systems may claim to offer either Euroclass B or C rating to EN 13501-1. However, to support a Classification Report from an independent notified testing body, previous simple fire test reports are no longer sufficient.

The description of the product or treatment given in the Classification Report has to be comparable with the exact specification of the timber components to be used in the project. For example, if a Classification Report for a fire retardant product or treatment refers to Euroclass B being achieved on 25mm thick spruce cladding 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 thick
• Alternative species
• With an air gap in place
• Other backing materials deemed to be ofhigher risk

The onus is on you as a specifier to ensure your supplier has a relevant and specific independent Classification Report to match your particular end use requirement.

Quality of Application

If fire retardant treatments are required for new timbers going into a building then by far the most effective are those that are applied in factory controlled conditions. Traditionally the timbers or panel products are given a measured, controlled, highly effective and permanent built-in protection through pressure impregnated treatments that are automatically applied to all areas of the timber.

Fire has the highest level of attestation in Europe and a supplier of fire retardant 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 this ISO 9001 accreditation.

Durability and Maintenance

When specifying you need to be assured that the fire retardant performance of the treated timbers will last in both interior and exterior end use applications.

Well-researched and specified FR timbers will provide a permanent fire protection within the timber structure that will not require further FR maintenance and are designed to meet the life of the building, providing effective and competitive life-time value.

Availability and Cost

There is always the temptation to change professional specifications from quality industrially applied fire retardant treated timbers to site applied or less accredited options because of tight deadlines or price considerations.

However, as the performance of FR treated timber can be a matter of life and death, it is therefore paramount that professional contractors resist the low cost, low performance, on-site options and build realistic productions schedules into any specification to allow for adequate factory processing.

Profiling of timbers, kiln drying and product supply by timber merchants can sometimes take between 2-4 weeks. Professionally applied and controlled fire retardant impregnation treatments will be around 4 weeks to supply because of the preparation for treatment and careful re-drying afterwards, giving a total procurement lead time of 6-8 weeks.

As an option some leading merchants are now offering ready available stocks of popular species and profiles of pressure treated fire retardant timber claddings and panel products which may provide an alternative option. However, be certain the specification meets your needs.

In terms of costs, controlled, factory applied treatments may be initially higher than on-site applied options. However, if the ‘whole life’ cost of the building and the timbers is considered in terms of regular maintenance and recoating required for some products, then the one-off pressure treatments then provide real value for money.

In summary, if you require a quality fire retardant protection for either interior or exterior timber applications that you can have real confidence in, then proven, factory applied treatments provide the answer. Controlled and end use specific protection with a ‘one-off’ and permanent protection which requires no further maintenance.

Jacqui Hughes is fire retardants manager at Lonza Wood Protection