What is Dry Rot
and How Can it Affect Your Home?

Clients ask me "What is dry rot?" a lot.

Presumably because they're not sure of the differences between wet and dry rot, and with timber forming large parts of our homes and the current trend towards kit homes and the popularity of timber frame homes in the 1980’s and 90’s they’re right to be concerned about rot to timbers (including wet rot as well as dry rot).

What is Dry Rot?

Dry rot is a fungus that grows in timbers once the timber reaches a certain moisture content. The general consensus is that timbers are prone to damage if the moisture content gets above 20% however dry rot, once established, can spread at moisture contents as low as 14-15%. Although it is generally accepted that for an outbreak to start the moisture content needs to be between 20-35% (wet rot generally requires timbers to have a moisture content of 40%).

Dry rot growth occurs between 0℃ - 26℃ with rapid growth occurring as low as 5℃ and it will die when exposed to temperatures of over 40℃ for even short periods.

The Mycelium (thin strands of hyphae that spread though timbers feeding on starch, sugars and moisture) typically reach beyond what visually appears to be affected timbers.

Dry rot can, on average, be expected to grow around 1meter per year but this will depend on local conditions within the property. If you imagine the roots of a tree spreading through the soil in you garden. Dry rot spreads in a similar way by sending out strands of hyphae into damp timbers. 

These hyphae branch off on numerous occasions forming a mat of mycelium which purpose is to feed the fungus. 

Over time a fruiting body will appear which incubates millions of spores until they are ready to be released into the air. Each of these spores is then sent off with a small food supply to try to grow on other timbers.

One of the biggest difficulties with dry rot is ensuring the feeder strands have been killed. 

What happens if you have dry Rot?

If you have dry rot in your home you'll need to get it removed!

But the biggest issue is making sure you've removed all of it, as you have to remove the affected timbers and parts of the visually unaffected timbers in order to avoid it’s reoccurrence.

Whereas wet rot can be stopped by simply removing the moisture source.

The Surveyors Role:

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As most surveys are surface examinations your residential surveyor needs to be aware of what types of buildings are high risk and what defects could potentially lead to the presence of dry rot

Hopefully this will have helped broaden your understanding of “what is dry rot” and help you see just how destructive it can be and why you really don’t want it in your home.

If you’re looking for a residential surveyor to provide you with a residential survey in County Antrim or County Down please request a call back and we’ll call you to discuss your requirements.

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