Wood working15.04.2014

Paint brings fire protection to sawn goods as primed.

Koskisen's Fire-retardant sawn timber is also available as primed.

Koskisen's Fire-retardant sawn timber is also available as primed.

A combination of fire retardant and paint developed by Teknos is an easy way to achieve fire-retardant sawn timber with the highest possible classification.

Teknos initially introduced its Teknosafe fire-retardant paint two years ago. The paint offers exterior cladding boards and interior panels the highest possible fire classification for construction products in Finland: B-s1, d0. Construction product classification B means that the product will have limited combustibility, s1 means very little smoke production, and d0 means that no flaming droplets are formed.

“The product really took off last July, when manufacturers of fire-retardant sawn timber were required to have the CE marking in accordance with classification 1,” explains Janne Ilo, Teknos’s sales representative.

There are currently four manufacturers in Finland who sell fire-retardant sawn timber, and Koskisen is one of them. Late last year, the company became the third Finnish manufacturer to receive certification.

Long-term protection using fire-retardant paint

The fire-retardant paint system is a four-stage process: first the timber is painted on four sides with a colourless wood preservative, and then the four sides are painted with TEKNOSAFE 2407 fire-retardant primer. This ensures fire protection also for the exterior surface of the ventilation gap, i.e. the back surface of the cladding boards. Finally, the sawn timber is treated as usual with opaque paint.

This treatment results in the highest possible fire-resistance classification, P1. The paint additionally gives the wood product good weather-resistance properties in a range of weather conditions and, above all, long-term fire resistance, as the maintenance interval for the TEKNOSAFE 2407 coating system is as long as 10 to 20 years. Even then, a regular coat of paint is enough to maintain the surface.

Result of extensive testing

The need for the product initially came about from the needs of a Norwegian company, as the only products available were various fire-retardant intumescent coatings, which have poor long-term performance.

“With this sudden need arising from a customer, Teknos took the bull by the horns and began developing a product that would offer long-term protection against fire,” says Ilo, recounting how the method was sparked.

Overall, the product development project lasted several years, and it is by no means over, as new products are continuously being developed and old ones improved. Testing also took its time, as that is the only way to be sure that the combination really works and that it is sustainable.

“The product has undergone NT Fire testing, various weather tests conducted by testing institutes, and Teknos’s own accelerated weather cabinet test and outdoor test, which involves monitoring the product at regular intervals in normal outdoor conditions in order to observe whether the paint dissolves on the surface of the exterior cladding,” says Ilo, explaining some of the testing methods for the paint combination.

Many benefits over other methods

Sawn timber treated with fire-retardant paint is an excellent alternative to other similar methods. For one thing, the entire exterior cladding can be made of the same fire classification material, which makes the work easier. In addition, fire-retardant exterior cladding boards can be delivered to the construction site either ready to install or almost ready, which means they are fire-protected already during construction.

Timber that has been treated with the combination of fire-retardant paints does not require fire-protection eaves or the 8 metres of protective distance from the next building. Firestops are also not needed in the ventilation gaps.

“In wooden construction of public buildings, exterior cladding treated with the fire-retardant combination appears to be the easiest and even the most economical option compared, for example, to installing fire dampers and making firestops,” says Ilo.

Wooden construction of public buildings and especially the use of fire-retardant timber have been on the rise in Finland in recent years, and proof of that is the fact that sales of fire-retardant paint tripled in 2013 compared to the previous year, and that so far this year the sales figures of last year have already been reached.