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What causes timber decay?

Timber decay can be a serious problem for buildings of all ages, and wood rot and insect infestations are often found in older properties and period homes. In short, the timber elements in a building can decay and rot as a result of adverse environmental conditions such as water leaks and prolonged exposure to damp or wetness.

If you are considering the purchase of a property and your home survey has flagged up timber decay, it’s important to understand the nature of the beast. Armed with information, you can decide whether and how to proceed with the transaction, and how to tackle the problem. At Cosey Homes, our experienced surveyors can advise on all building problems and carry out specific structural inspections to check the health (or otherwise) of the timber in the property.

Many living organisms use timber as food, and biological attack can take many forms. The most common and destructive types of timber decay are caused by Dry Rot, Wet Rot, Death Watch Beetle, Common Furniture Beetle and Powder-Post Beetle. Let’s take a look at each of these in turn.

Dry Rot

Dry rot is caused by a fungus called Serpula lacrymans. It can lie dormant in wood for years until the right conditions in terms of moisture, oxygen and nutrients present themselves. With a relative humidity of 95% and a moisture content in the timber of more than 20%, the fungus will bloom and start to cause decay. Be under no illusion that dry rot is a serious issue. It can destroy softwood timber and even hardwood can be affected.

Dry rot, in its mature stages, has a distinctive plate-shaped fruiting body that is orange with white edges. Greyish white threads (mycelium) help the dry rot to spread across other building materials including brickwork. Timber that has been affected by dry rot has a characteristic appearance. Usually light brown in colour, it is dry and brittle with cuboidal cracking. Learn more about dry rot infestations in our recent blog here.

Wet Rot

The vast majority of timber decay in buildings is caused by wet rot. Wet rot or cellar fungus (Coniophora puteana) can either result in timber darkening (known as brown rot) or timber bleaching (aka white rot). In order to thrive, this fungus requires the presence of persistently damp conditions with a moisture content of about 50-60%.

Although some fungi produce fruiting bodies that are similar to dry rot, the main evidence of a wet rot attack is usually found in the form of blackish brown strands. Similar to dry rot, there may also be cuboidal cracking present.

Death Watch Beetle

Large-sectioned hardwood timbers made from oak or elm that are already affected by wood rot are the most likely places you will find a death watch beetle infestation in a building. Older properties are therefore more at risk. For a death watch beetle (Xestobium rufovillosum) infestation to become established, damp conditions must be present. But even if the wood is subsequently drying out, the attack may still continue albeit at a slower rate.

Death watch beetles are most active during the spring when they emerge through bore holes that are around 3mm in diameter, leaving behind coarse bore dust. And in case you were wondering, the name derives from the distinctive tapping or ticking sound they make during the mating season that can often be heard in the dead of night, supposedly heralding tragedy according to ancient superstitions.

Common Furniture Beetle

Anobium punctatum is the common furniture beetle, better known as woodworm. While it much prefers the sapwood of softwoods and hardwoods, rot affected heartwoods may also be vulnerable to attack. Badly ventilated roof voids and damp areas in suspended timber ground floors are most at risk from woodworm attack.

The furniture beetle is at its most active between March and August when the weather is warm. Tiny bore holes of 1-2mm in diameter with gritty, cream coloured bore dust are its calling card.

Powder-Post Beetle

Finally, the powder-post beetle (Lyctus brunneus) attacks the sapwood of hardwoods such as oak, ash, chestnut and elm. Softwoods and older hardwoods are immune to damage from this wood-boring insect.

The powder-post beetle is active year-round, and loves buildings that are centrally heated. Tell-tale signs of a powder-post infestations are bore holes that are around 1.5mm in diameter, and very fine bore dust that resembles powder – hence its name.

Inspecting the building

If damp is an issue in the property, or you suspect fungal decay, it is essential to instruct a professional surveyor to inspect the building without delay to detect where the water is coming from and how extensive the timber damage is. The following checks should be carried out:

It should go without saying that if your property is affected by timber decay, professional guidance must be sought without delay. Cosey Homes have nearly 20 years’ experience in the surveying industry, having served thousands of clients with expert advice, quality reporting and outstanding customer service. Contact the Cosey Homes team today.

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UK Wide Chartered Surveyors
Cosey Homes offer the full range RICS home surveys from Level 1 - 3 with national coverage provided by our experienced local property surveying team.