Always an emotive subject and always in need of clarification. Whilst we all know that the timber buildings are not only attractive, but are also sustainable, economical and provide fast construction solutions; the assumption can be that because we use wood for fuel it must therefore burn easily! However, this is not strictly accurate. In reality, wood is selected as fuel because it burns slowly and at a predictable rate and these are the same qualities which make it a safe construction product in the event of fire and should give you confidence in your timber building.
The “charring rate” of a wood structure means the time needed for the wood to be burnt through. This can be calculated to determine the safety of a building or how long it will take to burn and weaken its structural integrity: a calculation of the “degree of redundancy” in the structure. As a result of the thermal properties of your timber building this can mean that the timber log will char on one side yet not even be warm just a few millimetres inside the log. These qualities contrasts with the unpredictable nature of other structural products such as steel; which heat up more uniformly and give rise to expansion and loss of strength over the whole section, or masonry which cracks and spalls. Fire-fighters prefer to enter a burning building made of timber because they are better able to estimate how long they will be able to remain safely inside. Timber will not fail dramatically like, for instance, reinforced concrete.