Dry rot in an RV can be caused by an undiscovered plumbing leak but is usually caused by a leak in the outer skin which lets rain water in.
Almost everyone is good about re-caulking the roof seams but that’s only part of prevention. Cracks can develop in the rim of plastic roof vents well above the seam.
Windows are a major source of water leaks. Especially the front overhang window on class Cs. RVers with RVs over ten years old should consider having all the windows removed and resealed.
Check all cargo and access doors for damaged caulk and loose screws.
Marker lights can be a neglected source of leaks. Make sure you check them each time you reseal the roof. And be sure you replace any broken or missing lenses.
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