The term "dry rot" is actually a misnomer because the decay is caused by certain fungi capable of carrying water into the wood they infest. The water can be transported far away from the source and the wood will often feel dry to the touch thus the term dry rot.
Gradually, the wood decomposes and its strength is lost. Such damage is often inconspicuous until it's final stages, working behind the paneling on the structural framing of the RV.
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. Consider replacing plastic vents with metal ones.
Marker lights are often the source of a leak. Make sure you at least check them each time your reseal the roof. And be sure you replace any broken or missing lenses.
Windows are a major source of water leaks. Especially the front overhang window on class Cs. Partly because they get the full force of rain while driving but mostly because they are too hard for most people to inspect. Or too easy to neglect. If your RV is over ten years old you might want to have all the windows removed and resealed.
Inspect your RV Regularly. On the outside, look for irregularities around window and door frames. If you have screws that won't stay tight you may have a problem. If the screws are rusted or corroded you DO have a problem and it's a good indication of dry rot.
A day or two after you've washed your RV or after a rain storm check along the bottom edges. If it is still wet you probably have a leak. Check it out.
On the inside, look for water marks on the ceiling especially around roof vents. Remove the vent flanges and air conditioner shrouds and look for discoloration in the wood. That's a sure sign of a leak and possible dry rot.
And, of course, check around the windows. Look for discoloration, softness of the paneling and loose screws.
Repairing a leak is only part of the repair. Make sure the wood is dry. If there is any sign of dry rot treat the wood with an antifungal solution. Regular household bleach will work but there are commercial formulas of disodium octaborate tetrahydrate or sodium borate with brand names of Bora-Care®, Guardian®, Jecta®, Shell-Guard®, Tim-bor®.
If the wood has decomposed enough that the screws won't hold, don't just put in longer screws! Git Rot, an epoxy like product, can rebuild dry rotted wood, but if you wait until the long screws won't hold there may not be enough wood left to rebuild.
No doubt dry rot is responsible for the early death of many Motorhomes, Fifth Wheels and Travel Trailers simply because it isn't spotted and repaired before it gets out of hand. Your RV doesn't have to be one them.
If you're battling dry rot, come in and talk with one of our parts consultants here at Rocky Mountain RV and Marine. They will be happy to help you!