Finding Hidden Water Damage Before You Buy a Used RV

Two hundred dollars of vinyl plank and a gallon of interior paint will hide almost every visual cue of a long-term leak. New flooring laid straight over a soft subfloor still feels firm underfoot for the first year because the plank spans the compromised area. A coat of paint over a stained ceiling panel erases the tea-colored ring that would have told you exactly where the roof penetration failed. Neither operation touches the actual damage, and neither takes a full weekend.

Understand that this is often not fraud. Plenty of sellers genuinely believe a leak they had repaired in 2022 was the end of the story, because the visible evidence went away when the ceiling got painted. Water in an RV enters at a roof penetration, a window corner, a slide seal, or a compartment door, then runs laterally along the floor or between wall layers until it finds a low point. Fixing the entry does nothing about the substrate that already went soft twelve feet away.

So the inspection strategy is simple. Ignore the surfaces a seller can refresh cheaply. Spend your time on the surfaces nobody bothers to refresh, because they are hidden, awkward, or expensive to access.

Call ahead and ask that the unit be left closed up until you arrive. Then open the door and stand in the doorway for ten seconds before you step in. A coach with active moisture in the walls or the subfloor has a specific smell, damp cardboard with an edge of mildew behind it, and that smell is strongest in the first breath of stagnant air. Once the windows and the roof vent have been open for twenty minutes, it is gone and you will not get it back that day.

Be equally suspicious of the opposite. A used RV that smells strongly of air freshener, carpet powder, or fresh paint on a warm day is masking something, and the mask is deliberate. Note it, and go check the compartments and the underbelly first, because that is where the smell will still be honest. Bay doors and the area under a dinette bench hold the odor long after the living space has aired out.

Use the heel of your hand, not a fingertip, and press with real weight. You are feeling for compliance, meaning the surface gives slightly and then springs back, which is what delaminated luan or softened decking does. A sound wall or floor feels dead solid with no travel at all. Work systematically rather than randomly, because water follows gravity and geometry, and the failure points are the same on almost every unit ever built.

On the walls, run a flat palm across the exterior in raking light while you are at it. A shadow line or a gentle wave that only appears when the sun is low is the outside face of a delaminated area, and delamination adjacent to a window corner or a slide opening is almost always a water story rather than a heat story on coastal and inland units.

Empty every exterior compartment and look at the floor of each one with a flashlight held low and sideways so the light rakes across the surface. Compartment floors are usually thin coated sheet material with no covering over them, which means nobody refinishes them and they record everything. Look for staining, swelling at the edges, rust weeping from a screw head, and a floor that flexes when you push down on it with a straight arm. Check the seal around each door and whether the drain holes are open.

Then get on the ground. The underbelly on most modern trailers and fifth wheels is a coroplast or vinyl sheet stapled or screwed to the frame, and it should be flat, dry, and intact. Sag between crossmembers means it is holding water or holding wet insulation. Patches, mismatched tape, or new fasteners in one area mean somebody has been in there. Water stains running down a frame rail from a specific point are a map to the entry above it.

While you are under there, look at the frame itself in the same areas. Wet insulation sitting against a steel crossmember for a couple of seasons produces surface rust in a distinctive band, and that band tells you how long the problem has existed better than the seller does.

Bring your own ladder and do not walk a roof you have not been given permission to walk, and not at all if the seller cannot tell you whether it is a walkable structure. From the top of the ladder you can see ninety percent of what matters. Look at every penetration individually: vent flanges, the AC gasket line, the antenna base, the refrigerator vent, the ladder mounts, the front and rear cap seams, and the termination bar along both edges.

What you are grading is the sealant, not the roof surface. On an inland valley or low desert unit, self-leveling lap sealant hardens, shrinks, and pulls away from the flange edge from thermal cycling, and the failure shows as a hairline crack running along the perimeter of a bead rather than a hole. Multiple layers of fresh sealant slathered over old cracked sealant is a maintenance shortcut that traps water underneath and tells you how the previous owner handled problems generally.

A pinless meter reads through the finished panel into the material behind it without leaving a mark, which is why it is the only way to survey a unit you do not own yet. It reads relative moisture content, so the technique is comparative. You establish a baseline in an area known to be dry, then work across the wall and the floor in a grid, and you are hunting for the readings that are meaningfully higher than that baseline rather than any absolute number.

This is how a wall that feels perfectly solid gets caught. Substrate can be carrying enough moisture to have already broken the adhesive bond and started rot without having lost enough structure to feel soft under a palm. It is also how the actual extent gets mapped, and the extent is routinely three to five times the area an owner points at. That mapping is what turns a vague worry into a repair number you can negotiate with.

When we run a pre-purchase inspection at the shop, this survey is the core of it, along with an entry point search, a roof and seal assessment, and a look at the frame and running gear. It runs $250 to $1,200 depending on the size and complexity of the unit.

Damage is a known quantity you can price. A prior repair of unknown quality is not, and it is worse news, because a repair that failed means the entry point was never actually found. Water jobs that come back are almost always jobs where somebody replaced the wet material and never traced the path. The second failure then happens behind the new material, which is more expensive to open than the original ever was.

Look for the tells. A section of flooring that does not match the rest, screws in a subfloor that are a different type or spacing than the factory used, interior trim with fresh caulk at one corner only, a wall panel that is a slightly different sheen, or butyl squeeze-out at one window and not the others. Ask directly what was done and who did it, and ask for the invoice. An owner who had it done properly kept the paperwork and will hand it over.

The decision rule is straightforward. Get the repair scoped and priced before you commit, then subtract that number plus a contingency from what you are willing to pay. Water damage is not automatically a reason to walk away from a unit that is otherwise well built and well equipped. It is a reason to stop paying the price of a dry unit for a wet one.

The contingency is not optional. Water jobs grow once the floor is open more often than they come in under scope, because the survey maps moisture and only teardown reveals how much of the substrate is actually gone. On a used purchase where you are the one absorbing that risk rather than a carrier, build in twenty to thirty percent above the scoped number before you decide what the unit is worth to you.

And if the seller will not allow an inspection, that is your answer. A private seller with a sound coach has no reason to refuse a few hours at a shop, and plenty of them will meet you halfway on the inspection cost because it sells the unit.