Hi, I have a friend (I know, sounds very cliché but it's actually true) who has rot in a couple of their panels (vertical). What I'm now wondering out of pure curiosity is whether rot can spread to other healthy wood or if it only stays with the "affected" panels?
Rot can indeed spread. It depends a bit on why it started, so first, you need to know why it occurred in the first place. If you don't address the cause of its initial occurrence, you won't get rid of it. However, it often works well to address the source of the rot and replace the damaged panel boards, which will hopefully resolve it simply and cheaply....
to call Anticimex