ProConsult Building Inspections Blog

Delignification in your roof space.
delignification of roof rafters and battens

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Whether you are buying or managing a home, buying or managing commercial property, or in need of an experienced chartered builder for consulting services, ProConsult Building Inspections has you covered.

Roof maintenance is vital in prolonging the structural integrity of your home. Your roof provides defence for you, your family, and the rest of your home against heat, wind, rain and every other element nature throws at us. Just some of the issues we identify during an interior roof inspection include; water ingress, damage or decay, ventilation, poor or faulty installation, and even critters. You don’t even want to know the damage a family of possums living in your roof can do.

One term you may not hear much, but we are on the lookout for is ‘delignification’.

Delignification is predominantly seen on roof tile battens in Perth. This can be due to the type of timber used, the age of the house, and the porosity of the roof tiles. Over time, and for a variety of reasons, tiles do become more porous. This is often evidenced by a white salt residue on the underside of the tiles, which has been left when dampness has dried out. Older clay tiles are more porous and more susceptible to these issues. Moss on the roof cover is a big contributing factor as this holds water. We also see increased moisture levels with the overlapping of two tiles on the battens.

Delignification of roof battens and rafters

Lignin is a natural chemical found in timber, which lends rigidity to the material.

Moisture and salt (remember, in Perth we all live quite near to the ocean) causes the lignin within the roof battens to break down, swell and appear furry and shredded. This is known as delignification. Battens affected by delignification are weakened and will continue to deteriorate if the area is not dried out. Rectification involves removing all moss from the roof cover. This is best done with a pressure washer.  

Top Tip: please make sure you do this from the top with the pressure washer pointing DOWN the roof to avoid flooding your house!!

Always ensure the roof is safe to walk on before attempting any cleaning yourself. Once normal maintenance has been attended to and the moss cleared, the roof cover may need seal spraying or coating to ensure longevity. A better flow through ventilation system within the roof void will also help.

Delignification of roof rafters and battens

Please note, if only the battens have been affected, this is not classed as a structural defect. It is only a structural issue if the rafters themselves have been adversely affected. Under Australian Standard 4349 (which we report under) this is classed as a major defect as if left unattended, worsening of the situation will occur.

Ultimately, the affected battens can be replaced in due course.

For more advice on delignification, proper ventilation in your roof space, or to book an inspection with a professional and qualified builder, contact us today.