The top material seems to resist water okay, the sides not at all. We just got it on when a typical southern summer storm hit with 2" of rain in about 45 min. I highly recommend a tarp under at least if you suspect a leak. We're restoring a 70s Winnebago and needed the extra help. If your rig is water tight then its great for uv protection. Goes on in about 20 min or less, not too hard, just be careful and appreciate the material it's made of. Hope it rolls up to fit in the storage bag.