Timber rot is a destructive decay that can significantly impact the structural integrity of a buildings, importantly as timber joists hold up floors and ceilings. It is primarily caused by fungal growth that thrives in certain moisture conditions. The understanding and identification of different types of rot are crucial for effective treatment and prevention.

Types of Timber Rot

Timber rot can be broadly classified into Brown Rot and White Rot.

Brown Rot

Brown rot, including Dry Rot (Serpula lacrymans) and Cellar Rot (Coniophora puteana), manifests as cuboidal cracking in the timber. It primarily consumes cellulose, leaving a brown residue that crumbles easily.

  • Recognition: Identifying brown rot early can prevent further damage, and treatment involves removing the source of moisture and replacing or treating affected timber.

Dry Rot (Serpula lacrymans)

Dry rot is a severe form of timber decay, caused by the fungus Serpula lacrymans. It is capable of growing across and through non-wood materials to reach timber, and can remain dormant yet viable in dry conditions for about a year. Dry rot is identifiable by a distinct mushroom smell and often rust-red spores. It is a fast-growing rot and needs to be dealt with promptly.

  • Germination: The fungus requires some amount of oxygen for germination but can thrive in less ventilated areas as it carries its own water supply.
  • Treatment: The key to treating dry rot is eliminating the source of moisture and ensuring good ventilation without blowing spores into other damp areas with timber.

Wet Rot, all other rot other than Dry Rot

Wet rot encompasses various types of rot other than dry rot, including certain brown rots and white rots. The name derives from the fact that these rots usually occur in conditions of persistent dampness.

White Rot

White rot, such as that caused by Phellinus contiguus (Window Rot), attacks both cellulose and lignin in the timber, leading to a fibrous, stringy appearance and cracks along the grain.

  • Manifestation: The distinct pattern of decay makes white rot identifiable, and like brown rot, treatment involves addressing the moisture source and affected timber.

Respiration and Moisture Perpetuation

Rots respire, releasing vapour and thereby increasing the moisture content in the surrounding area, often perpetuating the rot cycle. Some rots require more oxygen for this process, which is why ventilation can play a crucial role in managing rot by aiding the evaporation of moisture.

Common UK Timber Rots

Aside from Dry Rot and Cellar Rot, the UK sees a variety of other timber rots:

  • Window Rot (Phellinus contiguus): A type of white rot common in window frames.
  • A variety of Asterostroma species, Donkioporia, and Plaster Fungus: These are other common rots, each with unique characteristics and treatment requirements.

Treatment and Prevention

Identifying the root cause of moisture is paramount in treating timber rot. Once the moisture source is eliminated, supporting or replacing damaged timber is typically the necessary step. Regular inspection and maintenance, coupled with good ventilation and moisture management, are key to preventing timber rot and ensuring the longevity of wooden structures within buildings.


Timber rot is a prevalent issue that requires a nuanced understanding for effective treatment and prevention. Recognizing the signs of different types of rot, particularly dry rot, and taking swift action to eliminate moisture sources and enhance ventilation can significantly mitigate the risks and damages associated with timber rot.

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