Tap Test Your Own Sidewall in Twenty Minutes

This is the single most useful thing an RV owner can learn to do, it takes twenty minutes, and it costs nothing.

Delamination is bond failure between the outer skin and the substrate behind it. It becomes visible as bubbling, waviness or a soft area, but it becomes audible long before that. Which means you can find the real extent yourself, before anyone quotes you.

What you need

A coin, a knuckle, or the plastic handle of a screwdriver. Chalk or low tack tape for marking. That is it. Do not use anything metal and heavy, because you can damage gelcoat on an older coach.

Pick a time when the wall is not in direct sun. Hot fiberglass behaves differently and the sound changes.

How to do it

Work in a grid, roughly every three to four inches, across the whole wall rather than only around the area you are worried about. This matters. People tap around a visible bubble, find soft area around it, and conclude the damage is a foot across. Then they tap eight feet away and find it soft there too.

Listen for the change, not the absolute sound. A sound laminated panel returns a sharp, tight, short tap. It sounds solid because it is. Debonded laminate returns a duller, deeper sound with a slightly longer ring, because the skin is now free to vibrate independently.

Mark every point where the sound changes. When you are done you will have an outline. That outline is the real damage.

Some practical notes:

• Framing members give a different, sharper sound. You are hearing structure, not damage. They run vertically at regular intervals, so once you find the spacing you will recognise them.
• Windows, vents and access hatches change the sound around their perimeter. Ignore a few inches around any opening.
• The area right under an awning rail almost always sounds different, and that is frequently a genuine finding rather than an artefact.

Where damage starts

Almost always above where you find it, because water travels down inside a wall.

The usual entry points, in rough order of frequency:

• Front cap to sidewall seam, which takes highway wind pressure
• Roof to sidewall seam, particularly in the front third
• Awning rail fasteners, especially after any wind event
• Window and vent perimeters
• Any aftermarket hole someone drilled

So if you find debonding low on a wall, tap the area above it and check the seam above that. Repairing the low area without fixing the entry point is money spent twice.

What the sounds cost

At our posted rates, so you can put a number to what you find.

• Delamination repair, mapped area, $1,500 to $20,000 and up at 10 to 100 labor hours
• Fiberglass panel repair, localised, $750 to $12,000 and up at 4 to 60 hours
• Full panel replacement where substrate or framing has failed, $2,500 to $25,000 and up
• Wall and ceiling panel repair, interior side, $500 to $9,500

Body and paint labor at $210 per hour, paint materials at $55 per paint hour, 7.75 percent sales tax on parts and materials only.

The range is wide because the variable is area, and area is exactly what you have just measured. A two square foot debond is at the bottom of that range. A whole side is at the top.

What to do with your findings

Two things.

First, if the area is small and there is no visible water staining inside, get a moisture reading before you do anything. A dry debond is a rebond. A wet one is a substrate replacement and possibly a rot repair, and those are different jobs at different prices.

Second, take the outline to whoever quotes you and ask them to verify it. A shop that tap tests independently and arrives at a similar outline is doing the work. A shop that quotes from the visible bubble is going to come back to you with a change order.

Bring photographs of the marked outline. On an insurance claim they are useful evidence, because they establish extent before teardown and they show the finding was not invented after the fact.

When it is worth doing this on a coach you do not own yet

Every time. Before you buy anything laminated.

A seller with fresh sealant on the front cap seam and a wall that taps hollow across eight feet has a problem they may or may not know about. Twenty minutes with a coin tells you which conversation you are about to have, and it is a considerably cheaper twenty minutes than the alternative.