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 although we do see instances with other tiles. 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.
Lignin is a natural chemical found in timber, which lends rigidity to the material.
Moisture, salt (remember, in Perth we all live quite near to the ocean) and other pollutants in the air causes the lignin within the roof battens to break down, swell and appear furry and shredded. This is known as delignification.
How to avoid the growth of delignification
- Clean any moss off your roof. This is best done with a pressure washer. Please ensure the tile battens are safe to walk on and remember to point the water stream DOWNWARDS to avoid flooding your house
- Allow airflow through the roof space – install a gable vent or whirly bird to dry to air
- Vent exhaust vents outside the roof space to avoid build up of condensation
- Seal the roof tiles.
Should I be worried?
No. There is more information on the technical side of things, including the strength of these battens – in this post.
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