Wayne & Silver Estate Agents  _  Hampstead Estate Agents

What is dry rot?

Published: 10/08/2022

Dry rot is a fungal timber decay that occurs when wood gets too wet, and a wood-destroying fungus attacks the timber. ‘Too wet’ in this instance means a moisture content of over 20%.
Dry rot is the most serious type of fungal decay. It is extremely destructive as it spreads across the masonry in your home and destroys all of the timber in its path - regardless of whether it is a skirting board, door frame, structural or flooring. It can affect new and old properties and will be detrimental to the property if it is left untreated as the fungus can weaken the structural integrity of a building and increase the risk of collapse.
What is it caused by?
 When airborne spores come into contact with wet wood, dry rot occurs. The spores germinate and sprout grey root hyphae strands. In turn, these grow into mycelium which covers the wood in a thick substance not dissimilar to cotton wool. The fungus eats the timber and removes the moisture from it, leaving it in a hugely weakened state. The fungus then becomes a fruiting body and then sprouts more spores to continue the life cycle.
Unsurprisingly, the fungus thrives in damp, poorly ventilated, moist conditions. The cause of damp timber could be broken roof tiles, leaking washing machine, condensation, faulty drainage, leaking pipes, or penetrating damp, all situations in which fungi growth is likely.
How to identify it. 
 Your property will suffer more the longer you leave dry rot untreated. So naturally, it is important to identify signs of dry rot as soon as possible, with early detection key to eliminating the fungi.
You should look out for these key signs:
  • Look under stairs, in lofts and attics, behind plaster and in flooring. Dry rot is often found here because the fungus likes damp, dark conditions. 
  • A damp fungal smell.
  • Shrinking or warping timber. This is a sign that moisture has been removed. 
  • Cuboidal cracking across the grain of the wood.
  • Wood that looks dry and brittle, like it could crumble and break in your hand. 
Depending on what stage it is in its life cycle, the fungus will be present in different forms:
  • Spores – dry rot begins as a red-rust, orange, and brown-coloured spore dust.
  • Hyphae – once spores come into contact with wet timber, the spore will germinate to produce hyphae which are identifiable by fine grey strands that grow through the timber.
  • Mycelium – hyphae multiply and generate mycelium growth which is characterised by a white or grey cotton-wool-like substance that spreads across masonry in search of wood for food.
  • Sporophore – this is the fungus’s mushroom fruiting body. It is rust-red and orange in colour and looks like a flat, fleshy pancake. The sporophore releases new spores in order to begin the life cycle of the fungi again.
The solution.
 Once you have identified signs of dry rot, you should immediately have a dry rot survey undertaken to assess the full extent of the damage. If a surveyor finds dry rot, you will need to get a dry rot specialist to remove the infestation.
They will stop the source of the moisture and remove the damaged wood and the surrounding area. They will also treat the existing structural timbers to protect against further growth. Lastly, they will replace the damaged wood with pre-treated timber. Once the work is done, you should make sure the property and area are well ventilated or buy a dehumidifier.