Rot can occur anywhere on a wood structure. Four things are necessary for rot to occur.
- Wood (or other suitable substrate)
These four things combined create the conditions that allow fungi in the air (it is everywhere as many allergy sufferers know) to take root and begin breaking down the wood substrate. As long as these four conditions persist, rot will continue. Remove any one of these and rot will stop.
Removing the wood is one way to stop rot but often not feasible. Replacement by a substrate that would not rot (concrete for example) could be very expensive and difficult in an existing home. Eliminating oxygen and controlling the temperature are usually beyond our control. This leaves moisture.
Without moisture, rot cannot start or continue. This is why a good Home Inspector will identify ways for you to control moisture access to your home, i.e. maintaining clearance between shrubs and the siding on your home and the distance between the exterior covering on your home and the ground (we like to see 6-8 inches between the ground and any wood portions of your building), repair any leaks in your roof, increase ventilation inside the home, and stop any leaking drain pipes inside the house.
No moisture = no rot!