The twenty minute tap test that finds delamination before an adjuster does

Three conditions before a single tap. The wall has to be dry, right through, which after rain or a wash means at least a day. A damp laminate deadens the very difference you are listening for, and a wall that has been rinsed an hour ago will read solid across a void. Park level, because a coach sitting on a slope loads its sidewalls unevenly and a stressed panel and a bonded panel do not sound the same.

And get the sun off the panel. Direct sun does two things, both bad. It heats the skin so the adhesive layer softens and the hollow note tightens up towards a solid one, and it floods the surface with glare so the low angle look described further down becomes impossible. Early morning, late afternoon, or the shaded side of the unit. Work one wall at a time and finish it before moving, because a partial pass down two walls tells you almost nothing.

Start at the front lower corner of the wall and work in columns, bottom to top, then step sideways about a hand span and come back down. A hand span is close enough to six inches for this purpose and it is a distance your body already knows, which matters over a forty foot wall. Tapping at random finds big voids and misses every small one, because a void six inches across sits comfortably between two random taps.

Use the flat of your palm and the heel below it, not your knuckles. A palm covers area and reads vibration through the skin of your hand as much as through your ear, and on a windy day the feel is more reliable than the sound. Two or three taps per position, firm enough to move the panel slightly, not hard enough to flex it. Count the columns as you go and keep a rough tally, because twenty minutes disappears fast and you want to know whether you covered the wall or half of it.

A sound bond is short and dead. The panel absorbs the tap and gives nothing back, and your palm feels a small dull thud that stops the instant your hand does. Move to a void and the note lengthens and lifts. The skin has come away from the substrate behind it, so it now behaves like a drum head with air behind it, and it rings for a fraction of a second after the tap. Once you have heard the pair back to back the difference is unmistakable, which is why the first thing to do is find a patch of wall you are confident about and tap it a dozen times.

There is a third sound worth naming. Some panels give a note that is neither dead nor ringing: a soft, muddy, slightly crunchy response, often near the bottom of a wall. That is usually not an air void but wet or crushed core, lauan gone to pulp or a compressed foam block. It is a worse finding than a clean hollow, because a void can sometimes be injected and a pulped core has to come out. Mark it differently from the hollows.

A coin held on edge and tapped lightly against the wall gives a much finer signal than a palm. It concentrates the strike into a small area, so it resolves the boundary of a void to within an inch or so, which is exactly what you want once your palm has told you roughly where the edges are. Work the coin around the perimeter of a suspect patch in short taps and you can outline the void well enough to tape it.

The coin lies to you in three places. Over any fastener, screw head or backing plate it goes dead regardless of the bond, so a run of coin taps along an awning rail reads solid because you are tapping steel. Over a graphics decal, particularly a thick vinyl one with an air pocket under it, the coin rings and the wall behind is fine. And on a fiberglass gel coat surface a coin can leave a mark. Use it lightly, use it for boundaries rather than for discovery, and never use it as your only test.

Delamination is a water story before it is an adhesive story, so it starts wherever water gets behind the skin and then sits. Six locations account for the large majority of what turns up on intake at this shop, and an owner who taps only those six has already covered most of the risk on the wall. Work each one first, then run the full grid, because finding a void at a known origin tells you where to concentrate.

Tap below and to each side of every window frame corner, not just under the frame itself, because the corner is where a mitred frame gasket opens first and the water runs diagonally. Work the wall under each awning rail fastener individually. Check the flange around every slide opening, top and bottom, along with the wall for a hand span outboard of it. Run the lower belt line from front to back, where road spray and standing water both live. Tap the wall around each compartment door frame, since that frame is a hole in the laminate with a seal around it. And work the front cap seam where the cap laps the sidewall, which is the joint that takes the most flex on the road.

• Below and beside each window frame corner
• Under every awning rail fastener, individually
• At the slide flange, top and bottom, and a hand span outboard
• Along the lower belt line, front to back
• Around each compartment door frame
• At the front cap to sidewall seam

Stand at the front corner of the coach with your eye almost against the wall, so you are looking down the length of the panel at a very shallow angle, and find a hard horizontal line to reflect in it: a fence rail, a roof line, the edge of a building. Then move your head slowly up and down. A flat wall bends that reflected line smoothly. A delaminated wall bends it in steps, and the reflection ripples or breaks as it crosses the void.

This is the most sensitive test available to an owner and it takes ninety seconds. It finds shallow, wide separations that a palm reads as solid, because a void can be under tension and still hold its shape while the skin sits a fraction of a millimetre off true. Do it before the tap test and mark what you see, then tap those areas first. Repeat it from the rear corner, since a wave that hides in one direction of light often shows in the other. Late afternoon light at a low sun angle is the best condition for it, which is the one time the sun is useful here.

Owners collapse these two tests together and they should not. Walk the interior floor slowly in socks, putting your weight through your heel, and feel for give: a spot that flexes, dips or creaks under load. That is a soft subfloor, which is water in the deck laminate under your feet, and it is found by loading the panel rather than by striking it. Work the perimeter, the slide thresholds, under the fridge and around the shower pan.

A palm on an exterior wall is looking for something different: an air gap between skin and substrate in a vertical panel that carries no load. The two conditions often share a cause, because the same failed window or slide seal can wet a wall and a floor, but they do not share a repair. Subfloor work runs $500 to $8,500 across 4 to 35 hours. Sidewall delamination runs $1,500 to $20,000 plus across 10 to 100 hours. Finding one does not price the other, so record them separately.

Mark every finding with low tack painter's tape, applied as an outline around the patch rather than a cross over it. Two reasons. A marker on a gel coat or a painted sidewall is a second repair, and even a pencil leaves a graphite line in oxidised paint that will not polish out cleanly. Tape also lets you correct yourself: outlines get redrawn twice on a first pass, and a taped outline can move while an inked one cannot.

Then photograph in three ranges. A full wall shot from far enough back that every taped outline is visible in one frame, so the pattern is readable. A medium shot of each outline with a tape measure lying against the wall inside the frame. And a close shot of the nearest seal, seam or fastener uphill of each void, because that is the candidate source. Note the date, and note the weather for the previous week. That set is what turns an owner's afternoon into something a shop can quote against and an adjuster can read.

The test finds separation. It does not find water. A void can be bone dry, the residue of a heat cycle or a bad bond from the factory, and it will ring exactly like one holding a litre of standing water behind the skin. It cannot tell you whether the core behind the void is intact, wet or gone, and it cannot tell you whether the structural framing behind the core has begun to rot, which is the finding that moves a repair from a panel job to a rebuild.

It cannot date anything. A void the size of a dinner plate might be two months old or five years old, and nothing in the sound distinguishes them, which matters because betterment and depreciation arguments turn on age. It reads badly over fasteners, backing plates, interior cabinet runs and thick graphics, so a solid note in those places is not evidence of anything. And it says nothing at all about the roof, which is where most sidewall water begins. A tap test narrows the question. Moisture metering, an interior teardown at a suspect corner, or a borescope through a compartment wall answers it.

If the wall is clean and the reflection is straight, you have a documented baseline and a date, and repeating the pass every six months alongside the sealant cycle is genuinely worth more than the first pass was. If you found one small hollow at a window corner with no interior stain, the seal above it is the job, and /services/collision-structural/delamination-repair/ describes what a real fix involves so you can judge what you are being offered.

If you found soft floor, a muddy note low on a wall, or voids at more than one origin point, a palm has told you everything it can. An RV systems estimate at this shop is $150, credited against an authorised repair, and it covers slides, awnings, water, electrical and generator. Where the question is what is behind a wall rather than which system failed, an in depth diagnostic is one hour at $285, also credited against an authorised repair. Insurance walk-ins are welcome and we write the estimate. Bring the taped photographs and the dates: the pass you already did shortens ours.