chemical delignification
  • March 17, 2021
  • Effective Building
  • 0

Chemical delignification is a problem that’s usually undetected or covered up in Sydney. It’s generally detected during a pre-purchase building inspection or timber pest inspection. Once these are found, it can make or break the deal.

Before we have a thorough discussion on chemical delignification, let’s first understand what a timber is.

What is a Timber?

Timber makes a solid and very strong building material. But have you ever thought why is this so? The timber consists of millions of fibres that are held together by lignin, a naturally occurring organic polymer. It’s the natural glue that binds together the millions of fibres that stretch from end to end in the harvested timber.

The lignin material doesn’t just serve a bonding function. It also protects the timber fibres from insect infestation and other diseases. It’s that’s responsible for the durability of timber materials. 

When the binding material disintegrates, the timber begins to lose fine grains, strength, and durability. The fibres will begin to disintegrate and will acquire a “hairy” grain. Timber will lose its compressive and high tensile strength when it loses its lignin and it will no longer offer the structural integrity to keep the buildings safe.

What is Chemical Delignification?

Chemical delignification occurs when timber fibres break down due to lignin deterioration. The material is defibrated and becomes weak with a hairy texture. Delignification can be a minor or major deterioration. In minor delignification, the timber material may get a hairy surface texture without losing its strength and causing structural issues. So it’s practically functional.

However, if it’s extreme delignification, the timber material loses the structural loss of strength. Such a material no longer serves the function and must be replaced. If not, the roof or timber structure might cave in time and collapse.

Where Will I Find Chemical Delignification?

Chemical delignification is a problem associated with timber roof battens identified within the roof loft space during a pre-purchase building inspection. Although chemical delignification can affect other timbers within the roof loft space, due to the sectional size of the roof battens accompanied with their position within the roof loft space, they’re the first to suffect the effects of this chemical reaction. 

If a timber-framed roof had a roof tiled covering & timber battens, it would be fair to assume that a roof collapse would occur before any significant delignification happening to any structural framing members.

Although delignification has been associated with timbers with weak durability properties, here in Sydney, we have witnessed that delignification can also occur to durable timbers. 

Even if chemical delignification will take several years before collapse occurs, it will be classified as a major defect while conducting a pre-purchase building inspection. Due to the threat of the roof cover collapsing, it’s not recommended to walk on any roof cover when chemical delignification is identified.

What Causes Delignification?

There’s naturally occurring delignification such as those caused by fungi. Then, there’s chemical delignification which occurs when the timber is exposed to certain chemical triggers that will cause lignin and timber fibres deterioration. In Sydney, some of the most common causes of delignification in structural timber include the following:

  • Living nearby the sea or salty atmosphere exposes the wood grains to the chemical effect of saltiness.
  • If you live near arterial roads, the timber in your house will be exposed to vehicular pollution which will lead to fibre disintegration.
  • If you are living near factories, industrial plants, or chemical plants, the fumes from the industrial plants will find their way to your structural timber and cause gradual delignification.

Spotting and Managing Delignification

Spotting Delignification

Because structural timber is hugely hidden from view, chemical delignification isn’t always easy to spot. In most cases, it’s occurring behind the ceiling. A professional building inspection is an ideal way to see the structural issues on your property.

Managing Delignification

There are some protection measures that will successfully prevent or lessen chemical delignification such as wood sealing, oil application, and structural timber painting. These are best done during the building stage. These measures will reduce the exposure of your structural timber to airborne chemicals which slows down the process.

There are extreme cases that may require the complement replacement of the affected structure. This is often an expensive exercise that’s why prevention is the best bulwark against chemical delignification. If you suspect your timber structures are deteriorating or you’re planning to purchase a new property, ensure you hire a certified building inspector who’ll carry out a comprehensive inspection to identify the defects.

For more information about building inspection, visit our Help Centre.

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About Elie Farah

Elie Farah is a Building Consultant with over 25 years of experience in the property industry. Elie has specialised knowledge in development acquisitions, blue-chip properties and inspections, as well as flood-affected and waterfront properties, heritage buildings, bushfire management and existing use rights.

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