Delamination, Void Mapping and Injection

A laminated RV sidewall is a sandwich: an outer fiberglass or filon skin, a substrate layer of Luan or thin plywood, a block foam or aluminum framed core, and an interior finish panel. Those layers are bonded under pressure at the factory, not fastened. Delamination is adhesive failure between them. The skin stops carrying load with the core, and the wall loses stiffness even where the outside still looks intact. Pressing a delaminated area with a flat palm gives a hollow flex that a sound wall does not have.

Three causes account for nearly everything we see. Water intrusion from a failed window seal, roof penetration or clearance light is the most common, and it works top down. Heat cycling is second, and in Southern California it is a serious load: a dark graphics band on a south facing wall parked outside runs far hotter than ambient air, and years of expansion cycles fatigue the bond line. Third is impact, where a strike releases the bond well beyond the visible damage boundary.

Void mapping is percussion plus moisture data. A technician taps a grid across the panel with a plastic mallet or a knuckle and marks the transition where the tone goes hollow, then repeats vertically and horizontally to close the boundary in pencil on masking tape. Moisture readings go on the same map. The result is a scaled sketch with square inches on it, not the phrase 'bubble by the window' that so many outside estimates carry. Scope, method and price all follow from that sketch.

The map answers three questions. Is the substrate still sound, or is it delaminated because it is rotted, in which case adhesive has nothing to bond to. Does the void reach a structural member, a window opening or a slide out cutout, where the wall carries concentrated load. And is the void contained, or does it run past a seam into a second panel. A wet, rotted, load bearing void is not an injection candidate regardless of size, and saying so early saves the customer money.

Injection reintroduces adhesive into a dry void and then holds the sandwich together under uniform pressure while it cures. Access holes get drilled on a pattern through the outer skin, low viscosity structural epoxy is worked in progressively from the low point upward, and the surface is squeegeed to distribute it. Then the panel goes under a vacuum bag. The bag is the part that matters. Clamps and boards produce point pressure and a mottled bond, while a bagged panel sees even atmospheric pressure across the whole repair.

Cure is a hold, not a labor operation. Depending on the epoxy system and the shop temperature, the bag stays down eight to twenty four hours, and the bay is occupied the whole time. After the bag comes off, the access holes get filled, the surface is faired, and the area is refinished and blended into the adjacent panels. Because that refinish crosses into paint labor at $210 per hour plus paint supplies at $55 per paint hour, the finish work often exceeds the injection work on the invoice.

Panel replacement means cutting the skin at seam lines, removing the failed substrate, repairing or replacing framing, bonding a new Alpha Systems or equivalent panel, and refinishing across the full panel. It is the correct repair for a wet, rotted, structurally involved or very large void. Lead time is the constraint rather than labor. Color matched or profile specific panels commonly run three to six weeks from the manufacturer, and discontinued profiles sometimes require fabricating from a plain sheet and refinishing the entire side.

The crossover is usually a matter of area and moisture rather than a dollar threshold you can memorize. Small dry voids of a few square feet in a non structural zone favor injection by a wide margin. Voids past roughly fifteen to twenty square feet, or any wet void, close the gap fast, because injection prep, multiple bag cycles and a wide blend start to approach the cost of simply replacing the panel and refinishing once. The void map is what tells you which side of the line you are on.