Monday, January 30, 2023


What sealant should I use on my RV’s exterior?

Dear Dave,
I am starting to see some exterior sealant aging on my RV. What is the best exterior caulk to use? I get so many varied answers from friends, social media.… What does the expert say? —Wallace, 2020 Sunset Trails 18RD Traveler

Dear Wallace,
There are dozens of sealants available and just as many opinions on which are the best. First of all, the most important issue when it comes to resealing your rig is the removal of the old sealant and surface preparation. If it is just some aging and doesn’t look like the sealant is cracking or pulling apart, you can clean it and inspect it for potential leaks. I use Dawn dish soap (blue), as it is excellent on dirt and even tree sap. Remember the ducks, seals, etc., covered in oil in Alaska! A little of the soap in warm water and a light brush do a really nice job. If you need something a little heavier, WD-40 also works well to clean if used sparingly, as it can start to break down the sealant as well.

Pin holes or cracks in sealant

If you do see pin holes, cracks, or separation that might allow moisture to penetrate, you can apply a light amount of additional sealant to coat it. (I’ll cover the type shortly.) If the holes or cracks are severe, it is recommended to remove the sealant and start new. I use a heat gun on the lowest setting and a plastic putty knife. Be careful to not get the heat gun too close to damage the roof material. Use a light isopropyl to clean it.

Now, to stir the pot! You want to use a sealant that is designed for the type of material you are applying it to. I would believe your trailer has some type of rubber membrane, either EPDM or TPO, which you can tell by removing a roof vent interior frame. You should see some excess material tucked inside. If it is black on the backing it is EPDM; if it is the same color as the exterior, it typically is TPO.

I have worked on quite a few Winnebago units and they have a fiberglass roof material, so I have used the NuFlex 311 RV sealant, as this is recommended by Winnebago. In fact, they even have a suggested sealant chart available for each model and each application.

The sealant recommended is PN 185987-03-CHT, which is only available in bulk application; however, they sell the tubes in Customer Service. According to the NuFlex site, it is also recommended for TPO and EPDM.

Flexible sealant

Also important is to make sure the sealant dries pliable so it can flex with temperature changes and road vibration. Heng makes several products for sealants including the NuFlex 311, that many service centers recommend.

Dicor makes a sealant that is designed for rubber membranes. If your rubber membrane has a fleece lining underneath, it most likely is an Alpha product. They have a proprietary sealant for that.

If you are applying the product to the roof, you will want to use a self-leveling lap sealant that will flatten out after you spread it somewhat with a plastic putty knife. This will provide the best coverage. If it is being applied to the side, use a non-leveling sealant so it will not run down the side. You will still want to knock it down with a putty knife or your finger.

 You might also enjoy this from Dave 

What sealant should I use between coach and chassis?

Dear Dave,
The caulking is starting to yellow between the coach and the Chevy chassis on our Class C motorhome. I want to recaulk this with something that doesn’t yellow but stays white. What sealant should I use? Silicone or Dicor or…? Thanks, Dave. —Jerry, 2021 Thor Chateau 22b

Read Dave’s answer.

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

Read more from Dave here


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Left Coast Geek
12 days ago

I prefer urethane sealants like Geocel’s Pro Flex RV. Silicone based products are very hard to clean off, and leave the surface damaged such that nothing will stick properly.

John I
12 days ago

Agreed, Sikaflex 715 rv roof white sealant on top, and Sikaflex 221 on sidewalls, are hands down the best.

13 days ago

I am always skeptical whnever I see tubes of sealant with the word “silicone” on it. I will only use the white Sikaflex 715 on my Monaco fiberglass roof or the clear Sikaflex on the full body painted sides.

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