Dry Rot – an introduction

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A brief introduction to recognising wood rot

Dry wood is a naturally durable material which is resistant to most biological attacks. However, when the moisture content of the wood increases, and the damp conditions are prolonged the wood becomes vulnerable to attack.

Damp wood (above 20% moisture content) becomes a perfect habitat for wood-rotting fungi, which obtain their food by breaking down wood cells and in turn causing loss of strength of the wood.

Provided a building has a great design, good workmanship and the buildings maintenance is planned then preventing wood rotting fungi should not be an issue. However, in contrast, for many reasons, there are scenarios where an outbreak of wood rotting fungi are present and the following can help provide light on which type of wood-rotting fungi is present following undertaking immediate remedial measures to eliminate the source of dampness.

There are two types of wood rots: brown and white.

Brown rots – changes the colour of the wood to a darker colour and causes cracking across the grain of the wood. Very decayed wood when dry will crumble to dust.

White rots – the wood will become lighter and fibrous cause the wood to become lighter in colour and stringy in texture without any cross cracking.

All brown and white rots are collectively referred to as wet rots, with exception to one brown rot which is commonly referred to as dry rot (serpula lacrymans)

Whilst it is not really necessary to know all of the many species of wet rot, due to them having the same remedial measures. It is important to know the difference between the wet rots and the brown rot (dry rot)

The dry rot fungus has the incredible ability to spread far behind plaster and through wall materials such as brick. Effective remedial treatment can sometimes be much more expensive than wet rots.


Identifying fungal growths in buildings Dry Rot –
Fruit-bodies Yellow (young) or rusty redwith grey edges (mature),

then darkening with age.

Plate or bracket shape.

Mature surface has

shallow pores or folds.


Strands White to grey. Up to8 mm diameter.

Brittle when dry.


Mycelium White or grey sheetswith yellow or lilac tinges.

Tears in the direction of


(text sourced from RECOGNISING WOOD ROT AND



If you require our assistance with timber decay, its recognition and remedial please get in touch and we will be able to advise further.


DISCLAIMER: This article is for general information only and not intended as advice. Each project has its own set of unique circumstances, all potential issues should be investigated by a surveyor on a case by case basis before making any decision.

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