A traditional Handcrafted Log home offers superior performance and protection in a bushfire over a conventionally built home. The CFA recommends everyone living in bushfire prone areas to have a Bushfire Survival Plan, and have their property prepared. No matter if your plan is to leave early or to stay and fight the fire, a log home is a smart choice and offers very high survivability in both cases.
The thermal mass of log walls protects occupants inside the home from the intense radiant heat of the fire front. Logs can burn, however large diameter logs are difficult for fire to take hold of, take some time to do so, usually just char, and smoulder out once the direct heat / flame has been removed. When the fire front and radiant heat threat has passed, occupants can go outside and extinguish any spot fires etc. A handcrafted log home (unoccupied at the time) near Buxton Vic, survived the full force of the Black Saturday Bush Fires in 2009.
This Log Home survived the Black Saturday Bushfires unscathed.
At Alpine Log and Timber, we use large logs 350mm to 500mm in diameter. Log of this size require a constant flame to be applied for a long time before they would begin to catch fire and burn on their own. We build our ‘full scribe’ log walls with horizontally fitted logs that have no gaps between them, meaning flames cannot take hold easily. In a bushfire, a log wall subjected to flame will be scorched, but this scorching and charring produces a protective layer, the timber underneath retains its structural integrity. This protective char coat is like the effect created by some chemicals used as a fire retardant to protect materials and structures during fires. Damage caused by scorching can be later cleaned up effectively by sandblasting.
Compare this to conventional homes. Independent studies show heavy timber construction resists fire better than steel which can weaken when exposed to intense heat. The radiant heat of a bushfire front can be up to 1600⁰ Celsius, enough to cook brick mortar into powder, and collapse a steel structure. It is known that structural steel begins to soften around 425°C and loses about half of its strength at 650°C. Put simply, conventional construction can fail due to the radiant heat, regardless of whether it catches fire or not. Log Structures insulate effectively from radiant heat and take a long time to fail structurally if they do catch fire. The use of Full Round logs for the Log Trusses, Roof Beam’s, Veranda Posts, and Walls makes log structures a top choice for Safety.
Analysis conducted in Canada, United States, Germany, Finland and the Czech Republic subjected a ‘full scribe’ Log Wall 2.4 m high x 4.0m wide to a vigorous test, by placing it into a burning furnace at a temperature of 1100⁰ Celsius for a test time of 3 hours with a simulated roof load of 15kN per/m. The results speak for themselves. After 1 hour there was no recorded temperature change on the inside of the wall and after 2 hours the inside wall temperature had risen to only 48⁰ Celsius. Near the end of the test, at 2 hrs 54 mins, the wall (under simulated roof load) compressed by only 5mm in height. At the end of the 3-hour test, the fire had caused a maximum of only 25mm of charring at the extreme outer edge of the log wall. This test clearly established the capacity of a log wall to withstand intense heat and its capacity to retain structural integrity in fire conditions.
Alpine Design’s Plans and Alpine Log and Timber’s Structures are scrutinized by Building Inspectors, Engineers, and Council Planners to meet all their requirements and comply with the Australian Standard AS3959 (construction of buildings in bushfire-prone areas). We generally experience no problems building in BAL (bushfire attack level) 29 and lower, please contact us if you have questions about building in BAL 40 or BAL Flame Zone areas.
STUDY’S AND REPORTS UNDERTAKEN ON FIRE RESISTANCE OF LOG HOMES
Click on the links below for further information …
Fire Resistance of Log Walls, by Dalibor Houdek, Ph.D. International Log Builders Association – PDF
Fire Performance of Log Walls, prepared by the Technical Committee of the Log Homes Council – PDF