If the sidewall of your RV is starting to look like it has goosebumps — waves, bubbles, soft spots that seem to get bigger on a hot afternoon — that's delamination. And it is never "just cosmetic." That fiberglass skin is structural, and every day it sits separated, the damage is spreading underneath.
Most laminated RV sidewalls are a sandwich: a thin fiberglass skin on the outside, a luan plywood backing, foam or insulation in the middle, all glued together under pressure at the factory. Delamination is when that glue bond lets go and the skin starts floating free of the core. I've seen walls where you could slide your whole hand into the gap.
What causes it
Nine times out of ten, it's water. A window seal that dried out and cracked. The roof-to-sidewall seam where the caulk gave up. Beltline molding that let go. A skylight, a compartment door, a marker light — any penetration where water gets behind the fiberglass. It wicks into the luan, the wood fibers separate and swell, the adhesive bond dies, and the skin starts to bubble. Florida heat accelerates all of it.
The tenth time, it's pure glue failure: heat and age break the bond with no water involved at all. That distinction matters — dry, solid luan can be re-glued, but waterlogged, punky luan can't, and no adhesive will hold it. Know which one you have before you touch it.
Step 1: Map it honestly
Knock on the wall with your knuckles and listen. Solid laminate sounds sharp and dead. Delaminated wall sounds hollow, like tapping a drum. Do it on a hot afternoon when the bubbles are at their worst — heat makes the failed area expand, which is actually useful for finding the true boundary. Trace the outline with painter's tape so you can see the real size of it. Then scan the area with a pinless moisture meter like the Klein Tools ET140. If the meter pegs in the delaminated area, you have water in the wall and a leak to fix first. Period. No exceptions.
Step 2: Fix the leak before anything else
This is the step that decides whether the repair lasts. Nothing else you do matters until water stops getting in. Find the entry point — window frames, roof seams, beltline moldings, anything mounted through the wall — and reseal it. On horizontal roof surfaces I use Dicor self-leveling lap sealant; over a clean, dry, failed seam on a sidewall, Eternabond tape is a permanent answer. Then hose-test it hard and check for drips. Fixing delamination over an active leak is just scheduling the same repair twice.
Step 3: Dry it out
If the core is wet, epoxy will not bond to it. This is non-negotiable. Give the wall real drying time — days in shade and airflow. If the luan crumbles when you poke it, that section of core is done and no injection repair will hold it.
Step 4: Inject the epoxy
For small, dry delaminated spots — think a foot or two across, not a whole wall — injection works. Drill small holes, about 1/8 inch, through the fiberglass into the void: a ring around the perimeter about six inches apart, plus a couple inside the bubble. Inject epoxy resin from the bottom holes up, using large syringes, so air pushes out the top instead of getting trapped. Work in small batches. Once epoxy is mixed with hardener, the clock is running, and a cup of curing resin is useless to you.
Step 5: Clamp it like you mean it
This is the part people underestimate, and it's the whole repair. The epoxy has to be under sustained pressure for the full cure — 24 hours — or you don't get a bond. A flat sheet of plywood against the repair area, braced with 2x4s against something that will not move: another vehicle, a building, a tree. A roller and five minutes of pressing will not do it. Pressure for hours, or nothing.
Step 6: Finish it right
Fill the drill holes, touch up with gelcoat or matched paint, and reseal everything around the repair. Then hose-test the whole area again, hard.
What NOT to do
- Caulk it back. Caulk is a sealant, not an adhesive. Squirting sealant under a bubble hides the spot and does nothing structurally.
- Inject epoxy into wet wood. It won't bond, and you'll have sealed moisture inside a wall where it will keep rotting.
- Mix up a big batch of epoxy and try to work fast. Mix small, inject, mix again.
- Skip the clamping. No sustained pressure, no bond, no repair.
- Try to save a whole wall with injection. A small bubble is a DIY repair. A whole sidewall looking like a relief map is a panel job — know the difference before you start.
Delamination is one of those repairs that rewards honesty: be honest about the size of it, honest about whether water is still getting in, and honest about whether the core is sound enough to save. Get those three right and a small repair will hold for years. Get them wrong and you'll be staring at the same bubble next summer, only bigger.
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