One would expect that a leaking RV roof would cause a stain, bubble or wrinkle on the RV ceiling. Water has to go somewhere, right? Isn’t it reasonable to assume that a hole in your roof would manifest itself on the ceiling below?

Unluckily for you, dear RV owner, Recreational Vehicles follow their own rules, and no, major RV roof leaks do not always show up underneath. I’ve peeled off rubber roof membranes to expose 40-120 square feet of rotten, disintegrating OSB decking full of rusty staples, and there was nary so much as a wrinkle in the ceiling below. In fact, by the time you see a leak from below, it’s often too late.

Here’s What Causes the Dreaded “Soft Spot” in Your RV Roof

Most RVs have roof decking made of OSB (Oriented Strand Board), which is an engineered wood sheet product made of glue and compressed wood chips. When wet, OSB acts like a sponge, swelling and soaking up available water. The faces of OSB sheets are treated to make them water-resistant, but any cut edges are susceptible. Thanks (or no thanks) to capillary action, water can wick through OSB much like a paper towel.