I know that I have water damage to some extent on my recently purchased 2003 1161. Is there a simple method to discover the extent of decay or rot, and determine when major reconstruction is needed? When I knock on the Filon surface on various areas of camper it seems solid (that is no obviously weak or soft areas) As I recently mentioned on another thread, I did replace the lower step inside the door because it was noticeably weakened toward the outer-rear corner when I stepped on it, so I know I have (or at least had) some water getting in that lower-entry corner. If the skirt 1)"knocks" solid and 2)has no obvious soft spots; does it need replaced if there is no further leaking? The skirt isn't necessarily structural is it?
Regardless, I do realize I must seal it up to stop any current leaks and remain vigilant to prevent future water leaks. Part of my solution is to store it inside my barn, nice and dry when not in use.
Just how much water damage/rot is mechanically OK? I realize that there may likely be no consensus among the responses as this is very subjective and that some of the more zealous among us (with more time on their hands) might suggest zero tolerance for any imperfection.

Lance replaced both lower rear quarters on my 1121 a few years ago(under warrenty). Pushing in on the outside laminate should feel solid, If you feel anything giving(soft) to the pressure then there is deterioration in that area. The panels are available from Lance and can be replaced in sections.
JMTCW