Signs of Dry Rot

What are the first signs of dry rot in timber: Visible large brown cuboid damage in timber with thick strands would typical signs that the decay has been going on for an extended period.  Its fruiting body often occurs when the outbreak is distressed (It is the flower of the fungus).  Dry rot will not live in masonry (without a wood source), the strands bringing nutrients back to the main body to help balance its digestive system and can pass through weak mortar or render (often lime-based), but not solid stone or brickwork.

Dry rot affecting treated framing

Dry rot (Serpula Lacraymans) is the most critical wood-rotting fungus in Europe.  The name dry rot is misleading as the timber must be damp for it to occur. Initially, Dry rot is spread by spores which germination on woody matter. It requires an initial germination temperature of between 21 and 25┬░C preferred pH level in the acid to neutral range, limited air movement and suitable water supply (28-30%WMC).  You can get a smell sweet, musty order from the mycelium.  Therefore despite its negative reputation, dry rot has a high degree of sensitivity to its environment.

Once it has colonised the timber and started to break down the wood, it can survive in lower moisture contents (around 18-20%), which are lower than other wood-rotting fungi.  There is nothing dry about dry rot except its name and visual damage to the timber after the fungus has consumed the wood.  It is important that you get it investigated by a suitably qualified person.

Dry rot is dangerous as it compromises structural timbers.

  • Inspect to find the extent of the infection by carrying out exposure work were possible.
  • Cut off the source of water to the outbreak.  This can take time and is the main reason for preservative treatments.
  • Once the area of the outbreak has been exposed, then carry out necessary repairs to the affected timbers.


The Dry rot fungus Serpula Lacrymans is relatively simple to address provided you cut off its water supply.  Chemicals are commonly used to hold the situation until the area has dried out. We then carry out timber structural repairs. I am aware of some conflicting information available and can clarify your concerns.

We would like to help you and show you how treat dry rot infection in your Edinburgh property.