Sores are blown around in the wind, carried by insects, animals or unsuspecting humans until they come in contact with the timber. If the conditions for the growth of dry rot are present, it will attack and spread.
Spores land on the wood. They germinate and spread like roots (Mycelium)
As Mycelium grow by penetrating wood to feed and gain moisture they turn into a white growth called sporophores
Sporophores produce tiny spores which spread to other wood causing the fungus to spread to other wood and the cycle begins again