Demand for fire-proof timber scaffold boards is growing

Contracts for construction projects increasingly call for the use of timber scaffold boards with fire retardant properties. Whilst demand was driven originally by the North Sea Oil Industry, the use of flame retardant (FR) treated timber scaffold boards is also required by London Underground, the Power Industry and increasingly on major timber frame construction sites. FR treated scaffold boards are also a significant export market for UK producers, particularly to the Middle East. The safety and damage mitigation benefits of FR treatment is becoming widely recognised by insurance companies.  

Surface wear and FR treatment

Since scaffold boards are always subject to surface wear, only a flame retardant (FR) applied using a high-pressure impregnation process should be considered suitable. Industrial FR treatments are impregnated under controlled conditions within a sealed autoclave using a pre-determined vacuum and pressure cycle to force the chemicals into the cells of the wood. Brush or spray applied products offer only superficial protection which is quickly worn away under foot and should not be used.

Making the right FR choice for timber scaffold boards

In the UK, the Wood Protection Association(WPA) is the technical and advisory authority on flame retardants whose specifications are recognised by BSI, BRE, NBS, NHBC and the major fire test laboratories. The WPA categorises flame retardants into three specific ‘Types’ depending on whether they are to be used in Dry Interiors (Type: INT1); in areas prone to humidity or condensation (Type:INT2) or in external applications where leach resistance is an essential long term requirement: (Type: EXT).

For the treatment of timber scaffold boards WPA Type:INT2 applied by a pressure impregnation process is the treatment of choice. Type: EXT flame retardants may occasionally be used in certain limited applications. These are the only two suitable treatment systems:

 WPA Type: INT2 - Humidity resistant

WPA Type ‘INT2’ Humidity resistant FR treatments can be used in most interior and semi protected situations. Type:INT2 treated timber is far less sensitive to high or fluctuating humidity due to the lower solubility in water of the chemicals and degree of chemical interaction with the wood.

WPA Type: EXT - Leach resistant

Type EXT leach resistanttreated timber can be used in all interior and exterior situations exposed to humidity and direct wetting.

Additional benefits of these FR treatments

INT2 treatment does not result in any loss of strength and no additional safety precautions are necessary for handling FR treated timber scaffold boards over and above those for handling untreated boards.

‘WPA Approved’ Type ‘INT2’ and Type ‘EXT’ systems generate lower levels of smoke when compared with untreated timber.

In addition, independent testing carried out on the corrosion of metals in contact with FR treated timber show there is no more corrosion than with untreated timber.

Getting FR treatment specifications right first time

The WPA ‘Flame Retardant Specification Manual’ (free to download on is regarded as the best practice guide to the specification and use of industrial flame retardants in the UK and includes detailed FR product data and a simplified way of specifying treatment using the ‘WPA Commodity Code’ system. Scaffold Boards should be treated to WPA Commodity Specification FR4.

Alternatively, a buyer of FR treatments can specify in accordance with BS EN 13501-1:2002 (Euroclass B or Euroclass C levels of performance). This standard is now considered the norm for FR performance rather than the older BS476:7. Class 0 or Class 1standard.

Most contracts where FR treated timber scaffold boards are mandatory require Euroclass C surface spread of flame performance as the minimum standard of treatment. In high risk areas treatment may be needed to Euroclass ‘B’.

FR treatment Quality Assurance

Care should be taken when ordering materials to ensure that the supplier is able to offer a certificate of treatment and/or conformity and that this can be substantiated by an original test certificate from a UK recognised and accredited fire testing laboratory. Only FR products manufactured in accordance with ISO9001 quality assured procedures should be specified.

The WPA Benchmark of quality

The WPA operates a third-party quality assurance and product approval scheme for fire retardant treatments known as the WPA Benchmark. The National Association of Scaffolding Contractors (NASC) recommends that only FR treatments that are ‘WPA Approved’ should be used to fire-proof scaffold boards.

The treaters and products that have achieved certification/approval under the WPA Benchmark FR scheme can be found listed in the WPA FR Specification Manual (available as a free download) and on

(Below) Putting safety first Timber Scaffold boards treated with a WPA Approved FR and certificated under the WPA Benchmark FR quality scheme. Photo courtesy: Marley Eternit - JB FireSafe


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Posted at 9:32 am on May 17th, 2017