RV slide-out leaking when it rains: where the water gets in and what it costs to stop it

A slide-out that leaks every time it rains is the most expensive slow failure on an RV in Sebring, because the water goes into the slide floor, and the slide floor is thin plywood that rots in one wet season. The fix is almost always the seals or the topper: $200 to $800 for wiper and bulb seals, $300 to $900 for a topper, done at your site. Trip fee $75 to $150, and we look at the floor while we are there.

Check this first (ten minutes, next rain)

1. Where does the water show up? Along the top edge of the slide inside: the top wiper seal or the topper. Down one side: the side seals or a slide that is sitting slightly racked. At the floor: the bottom seal, or water that came in higher up and ran down inside the wall.
2. Slide in or out when it leaks? Out, during rain: seals. Coming in, after rain: the topper is dumping its pool. Both: probably both.
3. Look at the seals from outside with the slide out. The wiper seal (the flat blade that sweeps the slide box) should lie flat against the box with no cracks, curl, or black mildew lines. The bulb seal (the round one that compresses when the slide is in) should be round, not flattened, and not split.
4. Look at the topper. Standing water on it after rain means it has stretched or lost tension. Black mildew across the fabric means it has been holding water for a while.
5. Press the slide floor near the outside edge, inside the rig. Firm: good. Soft, spongy, or a musty smell: the floor has been wet for a while, and that changes the job.

What is usually wrong

Same figures as the pricing page, with labor at $125 to $190/hr inside those ranges.

Why this is worse here than almost anywhere

Slide seals are rubber, and rubber lives or dies on staying pliable. Sun dries it. Humidity mildews it. In Highlands County the seals get both: a July average high over 91°F on the sunny side of the rig, and 79 percent humidity that never lets the shaded side dry. The wiper seal curls, the bulb seal flattens and cracks, and black mildew grows along every edge where the seal meets the slide box.

Then the rain. Sebring takes about 52 inches a year, with June the wettest month, July having measurable rain on about 22 days, and June through September accounting for more than half the annual total. A slide with a marginal seal is wet, continuously, for four months. Water that gets past the top wiper runs down inside the wall to the slide floor. Water that gets past the bulb seal goes straight into the floor edge. Slide floors on most rigs are half-inch plywood over a steel or aluminum frame, with the bottom skin open to the weather. Wet plywood in a Florida summer is soft by September.

Resort rigs are the worst case, because the slide is out from November to April on the US 27 parks in Avon Park, Sebring, and Lake Placid, and then the owner leaves for the summer with it still out, or brings it in over seals that are already shot. Either way, nobody is watching when the June rains start.

What the repair involves

With the slide out, we replace the cracked or flattened seals, treat the survivors with a conditioner that actually stays on through humidity, check that the slide sits square in the opening so both sides compress evenly, and re-tension or replace the topper. We press the floor from inside and, if it is soft, show you before quoting the floor work separately, because that is a different job and you should see it before deciding.

If the slide is also slow or stalling, tell us; a slide floor that has swelled from water binds in the opening, and the two problems are usually one problem.

When to call

In April or May, before the June rains, if the seals have never been replaced or the topper pools water. Now, if there is water inside or a musty smell. We do these on site across Sebring, the Lorida fish camps, and out to Okeechobee, and the slide-out repair page covers the mechanical side.