Timber makes for a very strong, solid and durable building material but have you ever posed to think why this is so? The timber consists of millions of fibres that are held together by a naturally occurring organic polymer called lignin. It is the natural glue that binds together the millions of fibres that stretch from end to end in the trees and harvested timber.
The lignin material does not just serve a bonding function. It also protects the timber fibres from diseases and insect infestation. It is what is responsible for the durable quality of timber materials. It therefore goes without saying that when this binding material disintegrates, the timber begins to lose its useful qualities such as strength, durability and fine grains. The fibres will begin to disintegrate and the timber will acquire a “hairy” grain. Of the most significance is that the timber will lose its high tensile and compressive strength when it loses its lignin and it will no longer offer the structural integrity needed to keep buildings safe.
Delignification occurs when the timber fibres break down as a result of the deterioration of its lignin. The material is defibrated and becomes weak with a hairy texture. Delignification can be minor or a major deterioration. In minor delignification, the timber material may acquire a hairy surface texture without losing its strength and causing structural issues. So it is still practically functional. However, in extreme cases of delignification, the timber material loses it all leading to a structural loss of strength. Such a material no longer serves the function and must be replaced otherwise the roof or timber structure might cave in over time eventually leading to a collapse.
What Causes Delignification?
There is naturally occurring delignification such as those caused by fungi. Then there is chemical delignification which occurs when the timber is exposed to certain chemical triggers that will eventually cause a deterioration of the lignin and the timber fibres. In Australia, some of the most common causes of delignification in structural timber include the following:
- Living in close proximity to the sea or salty atmosphere exposes the wood grains to the chemical effect of the “saltiness”.
- If you live close to arterial roads, the timber in your house will be exposed to vehicular pollution which will slowly lead to the disintegration of the fibres.
- If you are living close to industrial plants, chemical plants or factories, the fumes from the industrial plants will find their way to your structural timber and cause gradual delignification.
Because structural timber is largely hidden from view, delignification is not always easy to spot. In most cases, it will be happening out of view behind the ceiling. A professional building inspection is generally the ideal way to unearth structural problems on your property.
There are certain protection measures that will successfully prevent or slow down delignification such as sealing the wood, applying oil or painting the structural timber. These are best done during the building stage. These measures will minimise the exposure of your structural timber to airborne chemicals thereby slowing down the process.
There are extreme cases that may require the complete replacement of the affected structure. This is often a costly exercise and that is why prevention is generally the best bulwark against delignification. If you suspect your timber structures are deteriorating or you are planning to purchase a new property, make sure you hire a building inspector who will carry out a comprehensive roof inspection to identify the weak links.