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Are there differences between fire retardant treated wood for indoor and fire retardant treated wood for outdoor use?

Yes, there are different classes of fire retardant treated wood: class INT for indoor use and class EXT for outdoor use. For EXT a surface treatment is generally required to withstand weathering. The classes are defined in the Nordic Standard NT Fire 054. A corresponding European standard is expected to be completed in 2010. Always insist on seeing documentation for class of fire retardant treatment.


Can fire retardant treated wood be classified as non-combustible?

No, organic materials cannot meet the requirements for non-combustibility, but fire retardant treated wood however can meet the highest standard for combustible materials, such as European Class B-s1, d0.


Can fire retardant treated wood have a finish applied and maintain the same fire rating?

Yes, but it may vary between different types of paint and paint sets, ask your supplier. Fire protection with colour/paint is always to be documented.


Does fire retardant affect carbonization velocity?

Fire retardant does not normally affect carbonization velocity, which is important especially for wooden constructions. Intumescent paints, however, sometimes delay the time until carbonization starts, but may be sensitive to wear.


How can I see if wood is fire retardant treated?

Fire retardants can be invisible, but the product must be labelled, preferably marked by piece or accompanied by product specifications.


How does a fire retardant work?

Fire retardants reduce the flammability, heat release and flame spread during a fire, which helps to reach a higher fire class. Fire retardants are primarily active for reaction to fire class, but higher fire class can also be achieved.


How is fire retardant construction waste handled?

As any other flammable construction waste.


How is maintenance of fire retardant treated wood performed?

The need for maintenance of fire retardant treated wood depends primarily on whether the product is used indoors or outdoors. It may also vary between different suppliers and products. Always ask for maintenance instructions from your supplier. Recommended maintenance indoors: Clean by dust wipe or wipe with damp cloth. Replace damaged panels. Regular Maintenance: Clean and seal damaged areas. Recommended maintenance for outdoors use: Establish a maintenance log. Clean damages to the paint and immediately cover with a new layer of a paint recommended by the supplier. Recoat in intervals accordance with instructions given by the supplier and with the paint recommended by the supplier. Clean before re-coating, but not with a pressure washer.


Is it possible to achieve a fire class with fire retardant treatment on a mounted wooden facade?

No, there is currently no treatment that can be applied on site and that can withstand weather exposure. 


What are the highest fire class that can be achieved by fire retardant treated wood?

Reaction to fire class B-s1, d0, ignition prevention cladding class K210, B-s1, d0 and facade fire tests in accordance with SP Fire 105 – Increased fire resistance of load-bearing and separating timber structures


What are the main areas of uses for fire retardant treated wood?

Internal walls and ceilings in residential buildings, evacuation routes and assembly rooms – Exterior cladding (provided that the fire retardant is weather-resistant, see question 7) – Ships and offshore installations


What is the cost of becoming a member of the NBT?

The membership fee for the upcoming fiscal year is decides at the annual general meeting.