By Floyd Mayberry
READER SUBMISSION TO RVTRAVEL.COM
I have seen posts on various RV forums inquiring about RV fiberglass damage known as “thermal checking.” I had never heard of this issue before experiencing it and have discovered the same to be true for most RV owners. I recently went through a massive and expensive repair to correct this type of damage, so I thought I’d pass along my experience. I am by no means an expert, just someone who now has a better insight into what causes thermal checking and how to address it.
Thermal checking in fiberglass occurs when the heat of the sun breaks down the surface of the fiberglass, creating fine cracks that first appear as white flicks in the paint (see photo). Thermal checking is more prevalent in darker colors since they tend to absorb more heat.
Sun-damaged clear coat only perpetuates this issue. In my RV’s cause, I had thermal checking and clear coat damage in several places along the left side of my 2005 motorhome, where it faces south while stored at home in the hot California sun. The damage is initially only considered to be cosmetic. If, however, it is left untreated, over time it can lead to major surface cracking and eventual wall delamination as the fiberglass begins to absorb moisture. This can take several years, depending on where you live. I personally could not ignore the way my RV looked any longer and decided to do something about it.
I spent a year researching the issue while gathering quotes from various RV body shops in my area. I discovered that the process was extremely expensive since it also involved a re-paint of the affected area. My wife and I talked it over and we decided to just re-paint the entire rig with a fresh new look. This, of course, significantly increased the cost of the repair.
Repairing and repainting the entire left side of our motorhome was going to run us $20,000. Painting the entire rig brought that total up to $33,000. One might ask why we would invest so much money in an older motorhome. This was a personal decision and there were many factors involved. We love our motorhome – it has been dependable and has treated us very well. Yes, a new motorhome would be nice, but we would need far more than $33k to purchase one. My wife and I are both retired, so it didn’t make sense to go back into debt for a new rig.
SOME BODY SHOPS repair thermal checking by sanding off the damaged layers of the fiberglass, then reglazing new fiberglass over the old. Some shops remove the old fiberglass panels entirely, installing new fiberglass in their place. The shop we chose did a full fiberglass replacement. All new fiberglass sounded better to us at the time, but it ultimately was the wrong decision, at least in our case.
Styrofoam is used to insulate most RV walls: It is glued in place between the exterior and interior walls. Because of this, when a shop removes a fiberglass wall panel, they end up inadvertently destroying the styrofoam at the same time, so it must be replaced. During this process, our shop somehow damaged our interior walls, creating small tears and cracks in many places. Our interior wallboard is no longer manufactured, so there was no easy way to repair this.
Since all of the damage ended up on the lower half of the walls, I suggested the shop install a wood veneer halfway up the walls, using a wood that matched our cabinetry. I instructed them to do the same to the opposing walls even though they weren’t damaged, so that the interior wouldn’t look awkward. This all turned out OK, and was done at the shop’s expense. If we had chosen a shop that merely sanded and reglazed the existing fiberglass, this would not have been an issue.
When my exterior fiberglass panels were originally installed by the RV manufacturer, they used a process called Vacu-Bond, which bonds the fiberglass panels to the wall structure with limited ripples in the surface of the fiberglass. Repair shops cannot employ this same method since the interior walls are already in place, so they use other methods such as clamping. I was assured that my exterior panels would be straight. Unfortunately, they have far more ripples than I had hoped for.
In hindsight, had I known what I now know, I would never have had my fiberglass panels replaced; I would have had them reglazed instead. There would have been no interior wall damage and fewer ripples on the outside.
THE BIG QUESTION
So the big question is, how can you as an RV owner prevent thermal checking from developing in the first place? The only effective way to prevent thermal checking is to keep your RV completely shaded from direct sunlight when it is not is use. This is not practical for many people, as it involves an RV garage or expensive indoor RV storage rental and it obviously can’t be accomplished by full-time RVers. Since thermal checking is heat damage from the sun, it is more prevalent in dryer climes with heavy sunshine.
You may never experience thermal checking if you live in a wet climate with mild summers. I religiously kept my RV waxed and covered it with a polypropylene RV cover while stored at home. Sadly, all of my hard work did very little to prevent thermal checking.
With all of this in mind, an informed RVer should consider paint schemes when purchasing their next RV. The darker the colors, the more susceptible to thermal checking that RV will be. When planning out our replacement paint scheme, we purposely chose lighter colors in hopes of preventing this from happening again.
Lastly, if you’ve been to an RV show or dealer recently, you’ll notice that a vast number of today’s RV paint schemes involve a great deal of black paint – the perfect target for thermal checking. I agree the black looks appealing, but I personally would not consider a black-painted RV for this very reason. Then again, I know folks that buy a new RV so frequently that their RV will develop thermal checking long after it’s been traded in on a new one! Keep this in mind if you are considering the purchase of a used RV. You might want to think twice if you come across one with visible thermal checking.