And like cancer, it's best to avoid the conditions that cause it. In the case of structures, the culprits are improper materials, flashing and design. Dryrot's name is a misnomer because the rot occurs in wet conditions, not dry. It occurs when water is allowed to penetrate wood in places and in a way where it won't dry out.
Wood destroying fungi require a food source, oxygen and favorable temperature in order to survive.
Moisture promotes fungi which increases wood permeability which allows moisture to penetrate further which encourages more decay, etc. etc. Wood strength decreases as the growth spreads. Most of the damage to structures is caused by brown rot. White Rot Wood decayed by white rot often assumes a bleached appearance, frequently has black lines through it and feels spongy. Wood strength decreases gradually.