--- title: "How to Check an RV Sidewall for Delamination by Hand" description: "Delamination is audible before it is visible. The palm pass, the tap boundary and the four places on a laminated wall where bond loss starts." focus_keyword: "how to check an rv sidewall for delamination by hand" canonical: https://ocrv.me/blog/what-a-delaminated-sidewall-sounds-like/ kind: blogPost updated: 2026-07-29 source: OCRV Center --- # What a Delaminated Sidewall Sounds Like Under a Flat Palm > By the time delamination shows as a bubble, the bond has been gone for a while. A **flat palm and a knuckle** map it early, and **extent decides the repair**, not appearance. ## How do you check an RV sidewall for delamination by hand? Slide a flat palm across the wall in overhead passes feeling for flex, then tap the boundaries with a knuckle to hear where bond loss starts and stops. Rancho Santa Margarita owners bring walls mapped this way to our Yorba Linda shop, which shortens the estimate considerably. - Use a flat palm, not fingertips, and work in horizontal passes - Tap to find edges, because sound changes at the bond line - Check below windows and above the belly seam first - Map the extent in chalk before anyone writes an estimate ### Key facts | Item | Value | | --- | --- | | Wall construction | Fiberglass over Azdel or lauan, foam core, aluminum frame | | Earliest detectable stage | Flex under a palm, no visible change | | Where it starts most often | Below a window, at the belly seam | | Body and paint labor | $210 per hour | | Written estimate | $150 (Credited in full against an authorized repair) | Every article about RV delamination shows the same photograph: a sidewall with a bulge in it that looks like a blister on a sunburn. That is a real and terminal stage, and by the time a wall looks like that the bond has been failing for two or three years. The useful window is much earlier, and it is not a visual window at all. A laminated wall is glued together. Delamination is glue failure, and glue failure changes how a panel responds to pressure and to vibration long before it changes how the panel looks. Both of those changes are detectable with a hand. Here is the method we use on incoming units, which takes about fifteen minutes per side. ## What is actually glued to what From outside in: a thin gelcoated fiberglass skin, then a backer sheet, then rigid foam block filling the spaces between aluminum framing members, then an interior wall panel. The whole assembly is vacuum bonded, which means it was pressed together with adhesive under vacuum in a press. There are no fasteners holding the skin on. Adhesive is the entire mechanism. The backer is the part worth knowing about, because it determines how the wall fails. Lauan is thin plywood and it swells, delaminates internally and then loses its grip on both neighbours. Azdel is a polypropylene composite that does not absorb water, so a wall built with Azdel tends to fail at the adhesive line rather than inside the backer itself. Different failures, different repair extents, same first symptom. ## The palm pass Place a flat hand on the wall with your fingers together and your palm making full contact. Push in gently, then slide the hand horizontally about eighteen inches and push again. Work across the wall in bands, from the belly seam up to the roof line, on a cool morning rather than a hot afternoon. Heat makes a laminated wall softer everywhere and it will lie to you. A bonded panel does not move. There is no give at all, because you are pressing on a foam block that is glued to a frame. A debonded panel deflects a small amount, perhaps a sixteenth of an inch, and it feels like pressing on the lid of a tin. You will know it immediately once you have felt the difference, and the difference is unmistakable within a single pass. - Flat palm, fingers together, full contact - Horizontal bands, roughly eighteen inches per step - Belly seam upward, both sides of the unit - Early morning, before the sun has been on the wall ## Finding the boundary with a knuckle Once you have found a region with give, switch to a single knuckle and tap. Over a bonded area the sound is tight and short. Over a debonded area it changes to something hollower with a faint ring, because the skin is now free to vibrate against an air gap instead of being damped by adhesive and foam. Work outward from the middle of the soft region in four directions and mark with chalk where the sound changes. What you produce is a rough outline, usually not a circle but an elongated shape following the framing bays or running downhill from a seam. That shape tells a technician more about the water path than any photograph, and it takes five minutes. ## Where bond failure starts on most units Below a window is first, by a wide margin. A window frame is a hole in the wall with a sealant joint around it, and the bottom of that joint is where water sits. Second is the belly seam where the sidewall meets the underbelly, particularly on fifth wheels where road spray works upward. Third is any exterior fixture screwed through the skin: an awning rail, a grab handle, a light, a table bracket. The fourth location surprises owners, which is directly under a slide room opening. The bottom edge of a slide opening takes water off the room every time it retracts wet, and the sealant there lives a hard life. On destination units that sit for months, that lower edge is the single most common place we find early bond loss. ## Two things that make it worse The first is drilling to inject adhesive from a kit. It works on very small isolated blisters and it fails on anything following a water path, because the void is not a bubble with a defined edge. Injection into a wet, migrating void bonds a small area, leaves the rest wet, and puts a permanent hole through your skin that has to be dealt with later. The second is pressing hard enough to feel better about it. A debonded skin with an inch of unsupported span will crack at the gelcoat if you push it repeatedly, and a crack turns a bond problem into a water entry problem. Test gently, mark the boundary, and stop touching it. > **warning:** Heat accelerates this failure. A wall with early bond loss parked with its damaged side facing south will progress noticeably over one Orange County summer. Turning the unit in a storage lot costs nothing. ## Why extent, not appearance, decides the repair A twelve inch region under one window is a localized repair: open a section, dry it, replace failed backer, rebond and refinish that panel with a blend into the adjacent one. A region running four feet along the belly seam is a different operation, because the repair boundary has to reach sound material and sound material is now a long way away. This is why mapping matters before an estimate is written. Two walls that look identical from ten feet, one with an eight inch void and one with a forty inch void, are separated by an order of magnitude in labor. The wall does not tell you which it is. Your hand does, in fifteen minutes, before anybody has committed to a number. ## What to do with your chalk outline Photograph it with a tape measure in the frame, and photograph the window, seam or fixture uphill from it in the same shot. Those two images are the beginning of a scope. If a claim is involved they are also dated evidence of extent before anybody took anything apart, which is worth a great deal later. Then decide honestly about time. Bond loss does not stabilize and it does not reverse. It progresses with heat, vibration and every additional water event. A wall mapped in March and left until the following March is reliably a bigger job, and the difference is usually larger than the cost of dealing with it in March. ## Questions and answers ### Why use a flat palm instead of fingertips to check a sidewall? Fingertips concentrate pressure into a small area and will find flex almost anywhere, including on sound walls. A flat palm spreads load across roughly forty square inches, which a properly bonded panel resists completely. The contrast between no movement and slight movement is what makes the test readable. ### Does an Azdel wall delaminate differently from a lauan wall? Yes. Lauan absorbs water, swells and separates internally, so failure includes the backer itself. Azdel is a polypropylene composite that does not absorb, so failure occurs at the adhesive line while the backer stays intact. Repair extent and drying time differ, though the first symptom feels the same. ### Do adhesive injection kits fix RV delamination? On a small isolated blister they can help. On a void that follows a water path they do not, because there is no defined edge to fill and the surrounding material is still wet. You end up with a bonded patch inside a failing area and a permanent hole through the exterior skin. ### Does sun exposure make delamination progress faster? Noticeably. Heat softens the adhesive and expands the trapped air and moisture in the void, which works the bond edge every day. A wall with early bond loss facing south in an Orange County storage lot will measurably worsen across one summer, and rotating the unit costs nothing. ### What should a photograph of suspected delamination include? The chalked boundary with a tape measure in frame, plus the window, seam or through fixture directly uphill of it in the same image. That pair establishes both extent and a likely entry point, and if a claim follows it is dated evidence recorded before anything was disassembled. --- Source: [OCRV Center](https://ocrv.me/blog/what-a-delaminated-sidewall-sounds-like/). Last verified 2026-07-29.