What is dry rot?

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Dry Rot is a fungus that eats away at the cellulose component within wood, turning it brown and ultimately reducing the timber to a dry and crumbly state with noticeable cuboidal fractures. It is caused when dampness combined with lack of ventilation provides the ideal conditions for fungal attack. It can affect all types of property, historic or modern and can grow within the cracks and cavities in the walls feeding off debris and wood behind the plaster.

Life-Cycle of Dry Rot

The life-cycle of dry rot can be broken down into four main stages. Dry rot begins as a microscopic spore which, in high enough concentrations, can resemble a fine orange dust. If the spores are subjected to sufficient moisture they will begin to grow fine white strands known as hyphae. As the hyphae germinate they will eventually form a large mass known as mycelium. The final stage is a fruiting body which pumps new spores out into the surrounding air.
Hyphae Phase

Hyphae Phase

Mycelium Phase

Mycelium Phase

Fruiting Body Phase

Fruiting Body Phase


Treating dry rot is a two-step process.

Step 1

Eliminate the source of water causing the damp. Possible sources:

  • Leaky plumbing, guttering or pipework including downspouts and overflows from CPL t/a CPL t/a CPL t/a Rainbow Internationalterns
  • Condensation
  • Rainwater coming through gaps in doors and windows
  • Damaged or ‘bridged’ DPC (damp proof course)
  • Missing roof tiles, flashing or cladding
  • Blocked air bricks

Step 2

Once the damp has been identified you’ll need to thoroughly ventilate the area using dehumidifiers and keeping the heat on low. This will take a while and remember, during this period the fungus can continue to spread.

Step 3

Get rid of all infected timber.

  • You’ll need to remove all affected areas of timber including a 60cm (24in) allowance either side of infection. Try to minimise the disruption of russet-coloured spores when removing timber and spray liberally with fungicide.
  • Structural woodwork such as joists should be replaced with new timbers treated in accordance with Eurocode 5. Cut ends should be re-treated and wrapped to physically prevent the spread of rot.
  • Healthy timbers near a site of infection should be treated with a preservative containing boron.
  • Affected plaster should be removed and replaced with fungicidal plaster. Masonry should be cleaned with a chemical fungicide and sprayed with a masonry biocide.

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For professional help in dealing with dry rot in commercial and residential properties, as well as a range of other industrial cleaning services, contact CPL t/a CPL t/a CPL t/a Rainbow International today for a free quote.