Fire and structural wood
There is no doubt that the general public is becoming more aware of sustainable and ecological construction with structural timber.
Even so, and despite the efforts of most of those involved, information of dubious quality can be found and a misuse of the sustainable and ecological definitions referring to construction, which can generate certain doubts.
Something that is common in our presentations, site visits and meetings with interested parties is the concern about the relationship between fire and wood in our buildings. We understand it, it is what is called an atavistic relationship, so I will try to dismantle the existing myths about it.
Dramatic and historical fires in antiquity, (London 1666, Rome 64 to give two well-known examples), have created an image that the relationship between both concepts, wood and fire, is unworkable. Although history has also shown us, (New York 2001, San Francisco 1906, p.e.), that steel, iron and concrete structures are, in similar situations, perhaps more dangerous.
The following information will provide you with knowledge that will eliminate your concerns about the relationship between fire and structural wood used in construction.
Wood, as a natural element, as a noble qualified material, offers advantages that make it a valuable element. Quite likely the structural element of the future.
Let’s get to it. These are, from our point of view, the four main arguments to deal with:
– Intoxication by inhalation of toxic gases
Did you know that most personal losses in a fire are caused by poisoning from inhalation of toxic gases, not burns?
Well, yes, they do. The gases emitted by the combustion of structural wood are much less harmful than the gases emitted by petroleum products such as polystyrene and polyurethane. This gas intake is more dangerous than the fire itself.
– The speed of propagation
Wood offers very low thermal conductivity, (Property of materials that quantifies the capacity to transmit heat through them), preventing the propagation. In fact, wood needs over 300º Centigrade of surface temperature in a sustained way to burn and the carbonization of the exterior layers acts as an insulating barrier, (up to 6 times more), which slows down the advance of the fire.
– Isolation and protection
Our constructions made with structural wood are equipped with added factors that increase the protection and in addition the fire resistance. In most cases, depending on the design applied, structural wood is protected by insulating elements such as rock wool fibres and fibre and plaster panels, whose main characteristics are thermal insulation, soundproofing and fire resistance.
– Structural modification by expansion
Steel, iron, are structural components widely used in «traditional» construction but have a very high thermal conductivity, being also materials very prone to expansion, which leads to weakened structures in case of fire being highly likely to collapse the structure. We all have impressive images in our retina caused by this effect.
On the other hand, structural wood not only has a very low thermal conductivity index, but it also has practically no expansion effect due to temperature, which makes it easier to mechanically maintain the spatial designs until the disaster is very advanced, thus allowing a possible evacuation.
We can see that although it might seem the opposite, structural wood offers very interesting and practical qualities such as reaction to fire, structural resistance to deformation, load and collapse in comparison with other materials.
If you have found this topic interesting or you want to know more about it I recommend the following articles.
I hope that the notes presented have served to minimize your concern and strengthen the confidence and interest in sustainable and ecological construction with structural wood and its relationship with fire.
In future articles we will try to expand the knowledge base of what for us is, without doubt, the future of construction.
If you want to contact us via email we will be happy to assist you, and if you want to expand your knowledge of sustainable and ecological construction visit our blog.
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Eco Construction Design.