Delignification, What it is and How to Avoid It

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Delignification, What it is and How to Avoid It

Termites and wood borers aren’t the only scourges likely to affect your structural timber. Another erosive but less well known problem that is likely to destroy your structural timber is timber delignification. It is something that you should closely watch out for. Ignore it at your own peril as it might lead to the compromising of the structural integrity of your building.

But what exactly is timber delignification and how can you avoid it in your structures?

Timber or wood is made up of millions of fibres that run through its entire length. The fibres are visible even by the naked eye. What is also visible is how closely these fibres have been bonded together to create a fairly strong and hard timber structure. The bonding of the timber fibres is due to a naturally occurring polymer that is referred to as lignin. It is the powerful natural glue that holds the timber fibres together.

But the lignin doesn’t just perform the bonding function. Other vital functions that it provides in timber materials include transporting moisture from the ground to the tree foliage and providing the tree with protection from insects and diseases. Even after the tree has been felled and the timber harvested and used in construction, the lignin still plays a crucial function in bonding the tree fibres and giving it its strong tensile and compressive strength.

If the lignin is destroyed, the tree fibres will begin pulling apart and the tree crumbles. As a result, the timber loses the advantages that the lignin material bestowed upon it such as strength and resistance to insects.

Delignification is therefore the process that occurs when the lignin is destroyed and the timber fibres begin to break down and develop a somewhat furry finish on the external surface of the affected timber. The timber material can suffer a minor delignification in which case, the structural integrity of the timber is not compromised in any way.

However, in extreme cases where a major delignification occurs, the timber is likely to experience a serious compromise in its structural integrity and there will be significant loss of strength. This usually occurs over a long period of time and may eventually cause the collapse of supporting structures such as the roof structures.

 

Causes of Delignification

Delignification can occur naturally when the timber is exposed to fungi. However, there are manmade factors that may accelerate the process. One of the most common scourges for many homeowners today is chemical delignification where chemical triggers speed up the breakdown of timber fibres and compromise the strength of buildings. It is a fairly common occurrence in Australia.

Some of the causative factors of timber delignification in Australia include the following:  

  • Where you house is exposed to salt in the atmosphere or you live in close proximity to the sea.
  • Living in close proximity to arterial roads which exposes your building timber to vehicular pollution.
  • Living in close proximity to factories, industrial plants or chemical plants

 

How to Avoid Delignification

One of the best ways to give your structural timbers a measure of protection from delignification is by ensuring that they are well oiled, sealed or painted. This will help minimise the exposure of lignified timber fibres to the corrosive airborne chemicals that cause delignification. However, this may not work in existing buildings where you may not get reasonable access to the timber to allow you to apply the oils or sealers.  

The kind of timber you use in your buildings may also dictate susceptibility to delignification. Softwoods are generally more susceptible to delignification than hardwoods. Where the damage is extreme, you may have to replace the affected timber to assure the structural integrity of your buildings. You should also carry out regular roof inspections so that you can spot any anomalies in time.   

 

By | 2018-07-31T03:24:08+00:00 October 19th, 2018|House Inspections|