Dear Dave,
My husband has done a terrific job of keeping our old RV looking new. The inside has been updated, and he is a mechanic so everything is kept in tiptop shape. For 15 years we lived in it full time and we have 150,000 miles on it. It is washed monthly using Johnson’s Baby Shampoo and waxed two times a year using Nu Finish. It is kept outside under a tree on our property but used at least every month now.
About a year ago we noted what looked to us like mold which seemed to be under the finish. It could not be cleaned off and was evenly distributed everywhere. The roof still looks great and does not leak. Recently, my husband was cleaning off the deck and aimed the pressure hose at the RV. He was using Olympic Deck Cleaner also. I worried about the pressure hose and the deck wash further harming the finish, but the upside is all the blue/black (mildew?) streaks are gone. There are still no leaks in the RV.
Was this dangerous to do?
My question is, was this a dangerous thing to do for what little is left of our finish on our RV? My husband was considering repainting the RV but feels like we don’t have to do that now. Did we just get lucky and happen on a way to rehab the outside of our RV? Or was this a dangerous thing to do? This morning is cool here in North Florida. He is going to start waxing today with Star brite wax. Please advise. —Sherry, 2005 Fleetwood Jamboree GT
Dear Sherry,
The short answer, in my opinion, is that pressure washers that are powerful enough to clean a deck are typically not good to use on an RV. That is because anything more than 2000 psi and/or 2 gallons per minute can peel back sealants and decals, and harm the finish. You can either dial down the pressure on the unloader of the pressure washer or use a different tip with a larger orifice that will reduce pressure at the nozzle.
So, I think you got lucky that no water got inside the rig and nothing happened to the finish. I do have a few concerns about the “mold under the finish.” I also have some questions on where the mold was, i.e., sidewall or roof, and what deck were you washing, which I will go into further below.
The long answer
Your 2005 Fleetwood Jamboree Class C motorhome would have had a one-piece fiberglass sidewall outer skin that was made by Crane Composites and was called Filon, or Kemlite. This is a layered laminate sheet with fiberglass fibers embedded into a resin with an outer layer of what is called gel coat.
Gel coat is a clear coating that helps protect the fiberglass laminate. In the late 1990s and early 2000s, most manufacturers used a very thin layer that produced a slightly dull finish called matte finish. They did this to hide the imperfections in the sidewall such as bulges from interior screws and a wavy sidewall. A high gloss finish would magnify those imperfections and not look good.
At some point, buyers started wanting the high gloss as it was more of an automotive finish. I could not believe they would overlook the bumps, waves, and imperfections just to get a high gloss finish—but the RV buyers drive the market. First impressions often sway the buying decision. A sparkling, high-gloss unit sitting beside a dull matte finish one just looks more impressive.
The roof material most likely was a rubber membrane, which would have been EPDM or maybe TPO. I assume you are referring to the sidewall material in the mold and waxing, since the rubber membrane would not be waxed. I bring this up only because you stated “The roof still looks great and does not leak.” And you also stated that your husband was cleaning off the deck and aimed it at the RV. So I hope your deck is at the entrance door level and not high enough to hit the roof, unless you are at a NASCAR track!
Why is there mold under the finish?
If there is mold on the sidewall, it would be under the wax that was applied and not under the gel coat. I would assume that the sidewall was not washed and treated with a fungicide prior to the application of the wax. Johnson’s Baby Shampoo may be too mild to wash the exterior of an RV. It does not have a fungicide ingredient that I know of.
Since you are under a tree, you are most likely in the shade. The cool, damp environment will cause mold and mildew to form, as you have found. What I do find a little odd is the roof looks great. It should also have mold unless it gets partial sun that dries it out, and the side with mold is facing the north, which most likely gets no sun most of the day. My guess is the Johnson’s Baby Shampoo did not take care of the mold and mildew spores and the wax applied makes it look as though the issue is underneath the wax.
I am not a big fan of using a pressure washer unless it is a low pressure (1200 psi) version, as you can blow off sealant and force water into windows, trim, and other areas.
My recommendations to clean RV exterior
A garden hose sprayer with a low pressure soap cannon is my favorite. I would suggest using Meguiar’s Gold Class Car Wash Shampoo & Conditioner. It is recommended for ceramic coating, so it will not do anything to wax or whatever coating is on the fiberglass. You can find it on Amazon here.
Use a soap cannon to completely coat the rig and then scrub with a microfiber cloth. You can find a soap cannon on Amazon here.
Filon recommends Meguiar’s #56 Marine – RV Pure Wax for their fiberglass. You can find that on Amazon here.
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What is best product to restore sun-faded RV fiberglass?
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What is the best way to get oxidation out of my RV’s fiberglass from sun damage? I see so many different products and tools for the job on the internet. I was hoping to do it without very expensive tools or specialty compounds that are hard to find. Or am I better off having it done professionally? —Joel, 2015 Winnebago Minnie Winnie, champagne color
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RVDT2788
Sheen vs. shine? Turns out many fiberglass RVs deliberately don’t have a shiny surface precisely because as Dave said, imperfections stand out. It’s the same reason why most houses use flat paint vs. glossy. Had an RVing friend who beat himself up trying to maintain a short lived shine on a 5th wheel that was meant not to shine. He learned the difference between dull and oxidized and works a lot less hard these days.
I have had good luck with removing mold and black streaks with Simple Green cleaner. I have used it with my pressure washer with a fine spray pattern rather than the pin point pattern which will remove decals!