The excellent fire-resistance of massive wood
Press release 07.12.2012
Massive wood is a fire-resistant material. In a fire test carried out by the VTT Expert Services of the VTT Technical Research Centre of Finland, a load-bearing Honka Fusion massive wood wall, 128 mm thick and made of non-settling logs, withstood a fire load for more than 90 minutes. In practice, this result means that a log house made of massive wood allows time to escape a fire as its load-bearing structures can withstand the heat of the fire for a long time without collapsing.
“In the test, it’s amazing how one side of the wall was engulfed in flames at a temperature of more than 1,000 °C, and at the same time the other side of the massive wood wall, the thickness of a just a couple of file binders, remained at a normal temperature and touchable with a bare hand for more than an hour and a half,” says Sanna Wester, Honka’s Vice President, Marketing, Design and R&D.
Honka Fusion is a high-quality innovation in wood construction, combining new-technology non-settling log structures with different materials, such as stone and glass, thus creating new kinds of massive wood buildings. Honka Fusion structures have been used in residential houses and vacation homes not only in Finland but also in Switzerland, France, Germany and Japan, as well as in restaurants and day-care centres in France, among other countries.
Log and massive wood construction innovations featured in the test wall
The result clearly exceeded previous fire test results for log walls. The fire-resistance of the test wall was as good as in a previous fire test where normal 40% thicker laminated log was used. This was the first time that the Honka non-settling Fusion laminated log was tested.
The test wall featured the new Honka Tech™ sealing solution as well as an innovative notch solution at log corners.
In the test, the Honka Fusion wall structure achieved the REI 90 fire resistance class. REI 90 means that the structure can be used in demanding buildings where load-bearing wall structures must be able to withstand fire for 90 minutes, be tight and be insulated against a rise in temperature.
Tight massive wood structure fire-safe and energy-efficient
A fire-tested wall structure is now available for Honka residential houses. “We have been working intensively on the tightness of log houses for a long time. Tightness is very important not only in terms of fire safety but also from the point of view of a house’s energy consumption,” says Honka’s Eino Hekali, M.Sc (Tech.).
Description of the test method: The test was conducted under standard SFS-EN 1365-1:1999 ‘Fire resistance tests for load-bearing elements’. In the test, one side of a load-bearing wall was engulfed in flames at a temperature in excess of 1,000 °C. The fire must not spread to the other side of the wall where, during the test, the temperature must not exceed 180 °C. With the Honka Fusion massive wood wall, the rise in temperature during the test did not exceed 10 °C, so the wall could be safely touched with a bare hand throughout the test. The very small temperature rise on the other side of the wall also demonstrated in practice the excellent thermal insulation capacity of wood. The fire test was performed by the VTT Expert Services Ltd.
VTT Expert Services Ltd: Fire resistance test on a loadbearing timber log wall, Test report No. VTT-S-04924-12, 2012
Ala-Outinen, Kajastila, Oksanen: Rakenteiden palotestaus eurooppalaisilla menetelmillä (structural fire-testing using European methods), Pelastustieto. Palo- ja pelastustieto ry. Vol. 58 (2007) No: Special edition, 37 – 41
The National Building Code of Finland E1: Fire safety of buildings, 2011