Water damage from moisture inside and leaks outside can do amazing damage on an RV, especially an older one. Phrannie’s Handling Moisture in RVs article is a great indepth, step-by-step description of what to look for in every part and piece of your trailer, motor home, or van to stop the drips, leaks, rot, mold, and mildew. The fixes range from emergency fast fixes on the road to more indepth ripping and tearing.
If you can take something that’s leaking apart, do it. Then seal the mating surfaces and put it back together. A “seal” can be a gasket (like under the air conditioner) or an RV putty tape (doors, windows, roof vents and the like) or “Kool Seal Patching Tape” (lots better that RV putty tape). However, smearing globs of caulking all over everything is not sealingâ€”and it doesn’t work.
“Caulking” is something you reserve only for things that can’t be fixed properly in the first place (or that you’re too lazy to fix properly). Caulking is also “insurance.” First you seal something (like a roof vent); then, for insurance, you caulk it to keep moisture from getting at the seal that does the real job.
“Coating” is the last step. After you’ve applied your sealing material and assembled things properly (without a lot of holes and gaps) and caulked (if necessary); then you coat the whole surface if appropriate.
Coating can be as simple as paint (prevents weathering, ultraviolet decay, rust and makes the thing look decent); or more complex (elastomerics that provide more durability and insulation) or more complicated and expensive (like custom-fitted vinyl sheetingâ€”the so-called “Rubber Roof”).
Fixing: There’s no point in doing any of the above unless you first repair structural defects. Impossible to cover all variations, but here are some that many people don’t consider.