Although the name states 'dry rot' the fungus needs damp conditions to begin and subsequently travel. A combination of damp conditions, humidity and inadequate ventilation are what cause dry rot to germinate and spread.
Dry rot typically occurs in the areas of a property that are not often seen, such as floor voids or behind timber panelling. Damage caused by dry rot may be extensive before the attack is discovered.
Initially the fungus appears as off-white, cotton-wool like substance on masonry and timber. In later stages, dry rot can develop fungal strands that resemble roots that you would associate with tree growth. Where the fungus is exposed to light, it often has a lemon-yellowish tinge. Damage is often confined to timber but large flat mushroom-like fruiting bodies can easily grow through finishes such as plaster or paint. These fruiting bodies may be the first visible sign of dry rot, and they produce numerous spores which are normally brick-red in colour.
Entirely dry rot decayed timber can be crumbled between your fingers. The fungus leaves deep cracks running across the grain, and there is often evidence of off-white residue of the fungus on the wood.
Removing the source of moisture should form the core of any dry rot eradication strategy. Timber can become damp for a number of reasons. Among the most common causes are:
- leaking washing machines, shower trays, baths
- condensation
- The dampness can also come from outside the building:
- leaking roofs
- rising damp
- dampness penetrating through walls
It is important that measures are taken to defend against re-infection. Any affected timbers should be removed and replaced with pre-treated timber. Any remaining timbers at risk of being affected by the dry rot should be treated with an effective fungicide.
Where the dry rot has passed through the masonry, it should be isolated using masonry sterilisation.