Saturday, September 30, 2023


I found a seemingly hollow area on my RV’s roof. Should I investigate?

Dear Dave,
I found what seems to be a hollow area on (under) the roof after washing the RV yesterday. I could not find any cracks or signs of any water leakage. It is forward of the rear A/C unit, next to the shower skylight, and behind a black(?) tank roof vent. It feels like it’s between roof joists. Questions: The ceiling has a hollow sounding area in the hallway, outside of the bathroom. Should I access this area from the inside, as the roof is a one-piece material? Is this something best left to the experts? Thank you, Dave! —Bill, 2019 Winnebago Sightseer 33C Class A

Dear Bill,
Your 2019 Winnebago Sightseer has a one-piece fiberglass roof material, so I doubt I would start cutting into that. The roof is made of the one-piece fiberglass material laminated to a thin piece of paneling called luan. These are laminated to a 3”-thick block foam insulation with perimeter metal framework and selected cross members. Then there is another thin luan panel and the interior ceiling material, which I believe yours is a padded vinyl.

Prewired components

There are several prewired components such as cables for solar panel installation, satellite dish, and other items. There are also cutouts for interior lights, vents, and speakers. Here are a couple of drawings of your roof from the Winnebago Owner Resources site. You can visit it here.

Click/tap to enlarge.
Click/tap to enlarge.

Usually there is a label indicating a buried cable or coax; however, they don’t stay on the roof very long. I would suggest visiting the site first to see if you can identify the hollow area and the corresponding diagram to see if you can identify what might be there.

Research further inside

If you want to research further, I would start with the inside and cut a small slit in the padded vinyl at the point where it is hollow and in the area you found the spot on the roof. Then you would need to cut the luan to access the block foam and the hollow area. It could also be a raceway for 120-volt wiring for a powered ceiling vent.

By cutting just a small slit, you can cover the area with a white plastic cover patch available at any home improvement store. We call these “dummy” plates, as cable or wiring is prewired in rooms and a blank plate covers the box they are in. I have also done a sideways cut and then covered the slit with a piece of wood trim or white trim going from side to side the entire length, which looks like the factory installed split trim.

Should you leave it up to an expert?

Like most of my suggestions, everyone needs to evaluate their level of expertise and comfort when working on your RV. When working on LP or 120-volt electricity, I suggest using a certified technician in that area. This DIY project is not as critical and, hopefully, you can identify a light fixture, speaker, or other component from the diagrams and not have to cut into it. Plus, if it is not leaking or causing any other structural integrity issues, you might just want to leave it as it is. Just make sure to periodically inspect the area inside and out to make sure nothing is changing.

 You might also enjoy this from Dave 

Soft spot on RV’s roof from broken vent seal. Can I just leave it?

Dear Dave,
I bought this unit used. There’s a soft spot on the RV’s roof where a seal around a vent was broken. Can I leave it, and will it stay “as is” if I keep it all sealed now? —Shawn, 2004 Newmar Mountain Aire

Read Dave’s answer.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

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Dave Solberg
Dave Solberg
Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


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1 month ago

If it poses no problem I wouldn’t touch it. However, for peace of mind, if you can gain access to that area, use a viewing scope to verify the void, A scope with a 3 foot reach can be purchased relatively cheaply at certain hardware chains.

Bill Byerly
1 month ago
Reply to  Ray

Makes great sense to me…

Bob P
1 month ago

For Shawn, if it ain’t broke don’t fix it!

Mikal H
1 month ago

If there is no sign of damage or leaking, I’d vote to leave it alone. If you must look, is there a removable bezel on the skylight that you stated this area is next to? If so, perhaps removing the bezel would provide some kind of access.

I would only cut into that padded vinyl ceiling as a last resort. Messing with that can cause an area of the padded vinyl to detach from the substrate forming a bubble. More common on older units, but a risk none-the-less. Don’t ask me how I know, as a former Winnebago owner.

Last edited 1 month ago by Mikal H

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