Fiberglass
Delamination Repair
In short: Delamination is the bond between the fiberglass skin and the substrate failing, almost always because water got in, and injecting adhesive into the gap treats the symptom while the wet wood behind it keeps rotting.
- Typical range
- $1,500 to $20,000+
- Labor hours
- 10 to 100 hours
- Updated
Delamination is the single most expensive thing that goes wrong with a recreational vehicle, and it is nearly always preventable. It is also the failure most owners misunderstand, because the visible symptom, a bubble or a ripple in the sidewall, appears long after the actual problem started.
What is happening inside the wall
An RV sidewall is a laminate: fiberglass or filon skin, adhesive, substrate of luan plywood or foam, framing, insulation, interior panel. It is strong because the layers act as one.
Water enters somewhere, and it always enters somewhere specific: a roof seam that has opened, a window frame whose sealant has cracked, a compartment door gasket, a marker light, a slide-out wiper seal, a poorly sealed accessory somebody screwed into the wall. It runs downward inside the cavity. The luan absorbs it and swells. The adhesive bond between substrate and skin fails. The skin, now unsupported, separates.
Then heat gets involved. The sun on a dark sidewall in California summer drives the trapped moisture to vapour, and vapour pressure pushes the separated skin outward. That is the bubble you eventually see, and by the time you see it the water has usually been in the wall for a year or more.
Why injection is not a repair
The injection kits sold for this work exactly as advertised: they inject adhesive into the void and clamp the skin flat. The bubble disappears.
What has not happened is any removal of the water, any replacement of the substrate that has already turned to pulp, or any correction of the leak that put it there. The wood keeps deteriorating, now sealed under a re-glued skin, and the framing behind it starts going the same way.
On a small separation with a documented dry cause, a hard knock that broke the bond without any water involved, injection is reasonable. That case is a small minority. On water-driven delamination it converts a $4,000 repair into an $18,000 one about two years later.
The actual repair
Find and fix the leak first. Everything else is pointless otherwise. This may mean roof work, reseating a window, replacing a slide seal or resealing compartment doors.
Map the extent. Tap testing and moisture metering across the whole wall, not just the visible area. The wet zone is always larger than the visible zone, usually by a lot, because water travels down and sideways inside the cavity.
Remove the skin. Cut back to sound, bonded, dry laminate.
Strip out failed material. Wet luan, degraded insulation, and any framing that has rotted. On bad cases this reaches the floor structure, because water ends up at the bottom.
Dry the structure. Genuinely dry, verified with a meter, not dry-looking. Re-laminating over damp framing repeats the failure.
Rebuild. New framing where required, new substrate, new insulation.
Re-laminate. New skin bonded with a tapered overlap into the surrounding sound laminate. Vacuum or mechanical clamping across the whole area while it cures.
Fair, prime, finish. Blended into the surrounding paint or gelcoat.
What it costs
| Extent | Typical range | Labor hours |
|---|---|---|
| Small area, under 4 sq ft, dry substrate | $1,500 to $3,500 | 10 to 20 |
| Sidewall section with substrate replacement | $4,000 to $9,000 | 25 to 50 |
| Full sidewall | $9,000 to $16,000 | 50 to 85 |
| Sidewall with framing and floor involvement | $14,000 to $20,000+ | 70 to 100+ |
Body labor is $210 per hour, paint $210 with supplies at $55 per paint hour. The pricing page has everything.
The spread is almost entirely a function of time. Water found in month three is a small repair. The same leak found in year three is a rebuild. There is no version of this that gets cheaper by waiting.
Where it shows up
Fifth wheel front caps and sidewalls, travel trailer sidewalls particularly below windows, Class A and Class C sidewalls, slide-out room faces which are exposed on all four edges and are the most common location of all, roof-to-sidewall transitions, and the lower sidewall on any unit that has spent time parked on a slope where water pools.
Lightweight and ultra-lite trailers delaminate faster than heavier units because the substrate is thinner and the framing is lighter. That is the trade for towing weight, and it means inspection intervals on a lightweight unit should be shorter, not longer.
Catching it early
Twice a year, press firmly along every sidewall in a grid pattern and listen while you tap. Solid laminate rings, delaminated laminate thuds and feels springy. Look along the wall in low sun, which reveals ripples that are invisible head on. Pay particular attention below every window, around every compartment door and marker light, and along both faces of every slide room.
Reseal proactively rather than reactively. A tube of sealant and an afternoon is the cheapest insurance available on a coach, and the failure it prevents is the most expensive one there is.
Estimates are $150 and credited back against an authorized repair. If you suspect delamination and want to know the extent before deciding anything, that is exactly what a hidden damage assessment is for.