Identifying Dry & Wet Rot

wooden roof

What is dry and wet rot? What problems can it cause in your home? How can you identify and remove it? Find out in our guide.

By Steve Hodgson

What Is Dry & Wet Rot?

Dry rot is only caused by serpula lacrymans (see page two for more details) and is the most serious form of fungal decay in a building. It can spread onto and destroy much of the timber.

Wet rot occurs more frequently, but is less serious; decay is typically confined to the area where timber has become and remains wet.

Why Does Wet Or Dry Rot Occur?

Outbreaks of dry rot and wet rot start in similar ways. The mature fruiting bodies of wood-destroying fungi that develop during an attack produce millions of microscopic spores and these are widely dispersed by air currents. If they fall on untreated damp wood they will germinate by pushing out a hollow tube called a hypha which grows and branches to form a mass of hyphal threads called mycelium.

This develops inside the timber and breaks down the wood for food. The timber may darken in colour and develop a characteristic cracked appearance. Some wet rots may result in bleaching of the wood; these are more common in doors and window frames. Eventually, the wood loses its strength and in some situations may become dangerously unsafe.

What Is The Difference?

The main differences between dry rot and wet rot are the degree of development of mycelium on the wood surface and the ability of the fungus to spread into other timbers via adjacent masonry. It is important that the two types of decay be distinguished since they require different treatment.

How To Treat Wet & Dry Rot?

Both need professional diagnosis and treatment. Use the links list below to find a firm that will do a good job for you.

Useful Links

The Royal Institution of Chartered Surveyors can help you find a local building surveyor contact via their website. And when making an appointment ensure the surveyor is experienced in carrying out tests and making recommendations regarding damp. Click here for recommended firms

The Property Care Association (PCA) was previously part of the British Wood Preserving and Damp Proofing Association (BWPDA), but became an independent association in 2006. They actively work to increase the standard of expertise of its members who are authorised to display the Association's logo in their advertising. They also offer a mediation procedure for the settlement of disputes.

Treat Damp website offers a huge range of low priced damp proofing products.

HSS offers a full damp proof course injection kit, a damp test meter and a wide range of other damp-related products for the DIY-er.

Steve Hodgson is the General Manager of the Property Care Association, which is a trade body which represents specialists in British wood preserving and damp proofing. For professionals in your area, go to


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