Delamination Repair: Cost, Hours and Process in Hacienda Heights

A laminated RV sidewall leaves the factory as six layers bonded into one assembly in a heated press: gel coat or paint, a fiberglass reinforced sheet, a bed of structural adhesive, luan plywood, a block foam core set between aluminum tube or wood studs, and the interior decorative panel. The stiffness of that wall comes from the bond, with the skin working in tension, the luan in compression and the foam holding the two apart.

That is the part owners rarely hear, and it changes how you should think about a bubble. The fiberglass skin by itself will flex in your hands. The luan by itself snaps. Bonded, the pair behaves like a beam. Break the bond over three square feet and you have not acquired a cosmetic blemish. You have a section of wall that has lost most of its bending stiffness, and every mile of road input from there on works the boundary of the void a little wider.

Delamination is the name for that specific failure. It is not rot, it is not a dent, and it is not a paint defect, and none of the three are fixed the same way. The visible bubble is only the skin relieving stress into an empty space that used to be full of adhesive.

• Gel coat or painted outer surface
• Fiberglass reinforced sheet, commonly Filon or Lamilux stock from Crane Composites
• Structural adhesive bond line, methacrylate or urethane
• Luan plywood underlayment, typically one eighth inch
• Block foam core between aluminum tube or wood studs
• Interior decorative wall panel

Water is first and accounts for most of what arrives here. It does not come through fiberglass. It comes through an opening: a window frame flange, a marker light, an awning rail, a slide flange, the roof to sidewall trim, or a screw hole somebody added for a bike rack. Water reaches the luan, the luan swells, and swollen luan releases from cured adhesive. The bubble shows up months or years later, usually below and often several feet sideways from where the water actually entered.

Heat cycling is second. Fiberglass and luan expand at different rates, so every hot afternoon puts shear stress into the adhesive between them. Dark graphics make it worse, because a black or deep red decal field runs thirty to fifty degrees hotter than the white next to it. That is why the first bubble so often appears directly under a stripe. A coach parked in the San Gabriel Valley with its long side facing west takes that cycle every day of the summer, which is a harsher duty cycle than the panel was validated against.

Third is a bond that was never good. Press dwell time, adhesive spread rate and surface cleanliness all vary on a production line, and a wall built on a bad morning can let go at four years with no water anywhere near it. We can usually tell at teardown, because the faces of the void are clean and dry rather than stained and swollen.

Fourth is impact. A strike that never breaks the skin can still shock the bond loose in a ring around the contact point, and that ring surfaces as a halo bubble weeks after the event. It is the reason we read the wall around any body repair rather than only the panel that got hit.

Diagnosis here is physical and the first tool is light. The coach comes out of the bay and the wall gets read with light raking along it at a low angle, which turns a wave you cannot see under overhead shop lighting into something obvious from thirty feet. The boundary gets chalked on the wall right then, because it will be invisible again by midday.

Second is a tap test. Bonded laminate returns a sharp report and a void returns a hollow one, and the transition is usually crisp enough to mark within an inch. Third is moisture. We read the luan through the interior panel and along the wall to floor joint on a grid against a dry baseline taken on the same coach, because the entire repair decision turns on wet versus dry rather than on how big the bubble looks.

Fourth is a look inside. Cabinet backs, the underside of a dinette bench and the wall behind a wardrobe tell you more about water history than the outside of the coach ever will. A stain line inside puts a date on the intrusion and tells us whether the framing is likely to be involved.

That work is what the collision teardown estimate at one hour of body rate buys, and it is credited against an authorized repair. We do not quote delamination from photographs sent in. A photograph shows a bubble. It says nothing about whether the luan behind it is dry, and that single fact separates a $3,000 job from a $15,000 one.

Injection is the repair owners want, and where it is appropriate it is genuinely good work rather than a shortcut. The sequence: mark the void, drill a grid of small ports through the fiberglass skin only, inject a low viscosity structural resin so it wets both faces of the void, then lay a vacuum bag over the panel and pull the skin down flat against the substrate while the resin cures. West System epoxy and ITW Plexus methacrylate are the two systems we use most, selected on void thickness and how much working time the area needs.

The vacuum is what separates a lasting repair from a seasonal one. Clamping boards flatten the middle of a bubble and leave the perimeter standing high, so the wall reads wavy in exactly the light that showed the problem in the first place. A bag applies even pressure across the whole area and pulls the skin back into plane.

Cure is the part nobody discusses. Structural resin cures on a temperature schedule, and pulling the bag early hands back the shape you just corrected. That is one reason this is bay work and cannot be anything else. The temperature of the building is part of the specification, not a convenience.

• The luan and core read dry on a grid, not merely dry to the touch
• The void is bounded and reachable from ports rather than open along a panel edge
• The luan itself is intact, not swollen, crumbling or separated into plies
• The skin is not crazed or cracked over the high point of the bubble
• The area runs roughly under ten to twelve square feet rather than most of a wall
• No previous injection has already filled the void with cured resin

When injection is out, the answer is to open the wall. The fiberglass skin is cut at a natural break, usually a trim line, a seam or a cutout edge, and peeled back off the substrate. Wet luan comes out. Crushed or shrunken foam comes out. Framing gets inspected, and where an aluminum tube has corroded through or a wood stud has gone soft it is replaced rather than boxed over. New luan and core go in, fresh adhesive is spread at the rate the system specifies, and the skin lays back down under vacuum.

Sometimes the skin does not survive removal. Old Filon that has been baking for eighteen years is brittle and will crack along a fastener line as it comes off. When that happens this becomes a panel job instead of a delamination job, and we tell you at teardown rather than at the end.

On cost, the band on this page is wide for one reason: the wet substrate boundary. A single dry bubble on a fifth wheel front wall sits near the bottom. A motorhome with two thirds of the driver side delaminated, wet luan from the roof line down to the floor and a corroded stud sits at the top and can pass it. Labor bills at the posted body and paint rate of $210 per hour across ten to a hundred plus hours.

The calendar runs longer than the labor because of drying. A wet wall gets opened, dried with managed airflow, then read again before anything is bonded, and that is days where nothing visible happens. It cannot be compressed, and the shops that skip it produce the repairs we get asked to redo two summers later.