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The Treatment

Russwood timber cladding can be pressure impregnated with NON-COM Exterior fire retardant under controlled conditions in a vacuum pressure impregnation plant. Further to kiln drying and high temperature curing the timber will then be returned to the optimal moisture content of 16-18% (+/- 2%) and will be ready for delivery to site.

When subjected to fire, the fire retardant in the timber will react with the combustible gases and tars normally generated by untreated wood and will convert them to carbon char, carbon dioxide and water. This insulating layer of char retards the process of combustion, dramatically reducing flame spread and heat release to allow people more time to escape, and limit fire damage. Additionally, less smoke will be generated – the primary cause of death in fires.

The Benefits

  • Consistent application guaranteed

    Factory conditions ensure a consistent level of protection, which may be more difficult to  achieve if an alternative treatment is applied by hand on-site

  • Leach-resistant

    The treatment is leach-resistant (as listed in the UK WPA Fire Retardant Manual) meaning that it can be used without a protective coating, allowing the cladding to weather naturally over time

  • No re-application

    The timber is impregnated on all faces and there is no requirement to re-apply the treatment during the  life of the timber

  • Non-corrosive

    The treated timber has been tested for its corrosive action on mild and galvanised steel and it has been shown that it does not contribute to the corrosion rates of these materials, so fixings should not be affected

  • Excellent stability

    Due to the ingredients being non-hygroscopic (i.e. they do not absorb moisture) this means that the treated timber can be used in projects where high/fluctuating humidity is an issue

  • Fire protection

    Dramatically slows down fire spread and reduces heat and smoke generation, saving lives and restricting fire damage costs

Timber Suitability

With the exception of Accoya®wood, all other Russwood timber cladding species are suitable for treatment with NON-COM Exterior. We do not currently offer timber which is painted and NON-COM Exterior fire-retardant treated, but this is something which we hope to make available in the future.

European Standards

The principal and most up-to-date European test and classification system for fire performance is BS EN 13501-1 (Fire Classification or Construction Products and Building Elements). In accordance with this system, NON-COM Exterior is fully tested and certified to achieve a Euroclass B/C fire performance.

Please note that this new Euroclass replaces the previous Class 0 (BS 476 Part 6 & 7) and Class 1 (BS 476 Part 7) and Euroclasses B and C are accepted by UK Building Regulations for timber in place of the National Standards of Class 0/1.

NHBC Building Control Service

NON-COM Exterior is accepted by the National House-Building Council (NHBC) Building control service for exterior cladding timbers, based on its excellent durability of over 30 years. It is also the only leach resistant treatment approved by the UK Wood Protection Association.

Internal Fire Retardant Impregnation

NON-COM Exterior is recommended for use with external cladding. If Russwood products are to be used internally, for example for panelling or sarking, we would recommend factory impregnation with Dricon instead – this is a similar product to NON-COM Exterior but is formulated specifically for use in internal and weather protected situations.


Full assistance with the writing of fire retardant treated timber cladding specifications is available on request. Please contact us.