What is Chemical Delignification?
Prior to the early 1990's chemical Delignifaction was referred to by many as Hairy Timber.
Chemical Delignification describes the deterioration in it's true form, the lignin in timber is damaged by airborne chemicals.
Lignin is the natural glue that holds the fibres of wood together and is therefore a major component of any wood. When the lignin is broken down or damaged the fibres then detach from each other creating a visible hairy surface to a section of the timber, as the delignification progresses the structure of the timber section is weakened and therefore Chemical Delignification is regarded as a structural pest of timber in service.
Chemical Delignification damage is most commonly found in timber sections used as roof tile battens of buildings that are located in close proximity to the sea, large chemical factories or major arterial roads that have heavy traffic.
Chemical Delignification generally will not occur to timbers in service that are sealed, painted or well oiled as the lignin is protected from airborne chemical substances.
When chemical Delignification is found in roof tile battens or rafters then it is recommended not have persons walk on the roof as collapse may occur and therefore a fall could cause bodily injury.
The photo below is a great example of how Chemical Delignification can affect the timber roof battens found supporting the roof tiles.