What is Dry Rot? Causes and Dry Rot Treatment in Ireland

This article covers how to identify dry rot, what the causes are, and dry rot treatments in Ireland.Dry rot in Ireland is a particular problem because our Irish climate is ideal for the germination and growth of the fungus.

Serpula Lacrymann, or “dry rot” as its more commonly known, is a fungus which attacks and breaks down wood. If left untreated, dry rot can spread and cause serious problems to buildings.

What is Dry Rot?

Dry rot is a type of brown fungus named after the colour it turns affected wood. The process of dry rot attacks and breaks down the cellulose in wood, and gives it the characteristic dark brown colour.

Indications of a dry rot outbreak include:

  • Cuboidal cracking – this is caused by the removal of moisture from the wood, this is an indicator of a brown rot attack.

  • Dry timber – crumbles easily between fingers.

  • Strands within the fungus (hyphae strands) are grey/white in colour, c. 2.8mm in thickness.

  • Fleshy fruiting body – Pancake shape, red/brown colour, due to spore covering.

  • Mushroom like odour

Cuboidal Cracking

Cuboidal Cracking

There are three conditions under which dry rot will grow:

  1. Warm, moderate temperature :- The ideal temperature for dry rot to flourish is 16 – 18 degree celsius, temperatures above 40 degrees celsius will kill the fungus.
  2. Source of timber :- Nutrient rich timber, such as sapwood timber, is ideal for the fungus to propagate.
  3. Source of moisture :- Despite its name, dry rot needs damp conditions to survive, wood with a 28% – 30% moisture content is ideal for the fungus to grow
Case of Extreme Dry Rot

Case of Extreme Dry Rot

Because of the conditions under which dry rot grows best, it often goes unnoticed for some time. Dry rot favours dark, humid, stagnant areas, such as, underneath stairs, behind cupboards and up in attic spaces, these are all prime locations for a dry rot problem to develop. If undetected, dry rot can grow up to two meters per year. Its roots may also travel over mortar and other areas to seek out new wood to infect. Dry rot has been known to spread through a number of attics within a row of terraced houses.

If you suspect your premises has been affected by dry rot, it is very important to call a damp proof/ dry rot specialist for curing dry rot, wet rot or other fungicidal problems. If not treated correctly, dry rot fungus has been known to remain dormant in materials such as mortar blocks for up to 12 months, and will spread again, once the conditions are right. Protum Ltd. use specialist dry rot chemicals as well as specialist application and chemical injection methods.

Brown Fungus

Brown Fungus

Dry Rot Treatment at Holyrood Palace

A famous case of dry rot was at Holyrood Palace,the Edinburgh residence of the Queen. The building was commissioned in 1498 by King James IV and later reconstructed to its present day glory by King Charles II. It was also the residence of Mary Queen of Scots from 1561 to 1567.
Stuart McAlpine a dry rot specialist, was contracted to carry out the work. He began by identifying the affected area, and removing the source of moisture. The moisture had entered the building through a leak in the roof.
All the timber in the affected area was tested for structural integrity, and the unsound timber was removed, and replaced with concrete lintels.
A number of preventative measures were also employed to reduce the possibility of dry rot returning. All the rubble was removed from the site, as it contained dry rot spores, and all affected plaster work and framing were removed.
Affected masonry and stonework were treated with specialist chemicals, and a fungicidal gel was applied to all timbers which were in contact with damp walls.

Dry rot in a building can lead to many problems. If you suspect that you have a dry rot problem make sure you contact an expert to take care of the problem.





  1. […] It relies on a high moisture content within the wood to survive, typically above 40%. Like dry rot it thrives in dark, stagnant, moisture rich areas, so weather conditions are ideal for wet rot to […]

  2. Great post on Dry Rot! dry rot is a major building decay fungus and is one of the most insidious and destructive problems a property can have. It can really eat away at the structure of your building if left to a long period!

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