By Chris Dougherty
Chris Dougherty is a certified RV technician. Here is a letter he received from a reader while he was serving as RVtravel.com’s technical editor.
When inspecting the roof on my Rockwood travel trailer I have noticed some areas of sealant that cause some slight concern, such as cracking. Am I able to apply new sealant over the old or does the old sealant need to be removed first. —Charlie
Yes, you can absolutely put sealant over old IF:
•The sealant on the roof is solid, not peeling up, and is affixed to the roof. Try picking at it. If it peels up, or you see signs of dirt under the sealant, then it should be removed and replaced. If its hard to remove, leave it in place and seal over it.
•The roof and sealant are clean. Cleaning the old sealant first is essential. Clean the area with an RV roof cleaner, and follow up with a good rinse with a wet sponge, then once dry, clean the area with a rag soaked with denatured alcohol.
•A couple of other points. First, use the right type of sealant. Some TPO roofs won’t react well to common lap sealants on the market, so be sure to use the product recommended for the particular roof material you have on your roof. If you’re not sure, you can contact your RV’s manufacturer, although your owner’s packet should have the information you need.
Second, be sure to use self-leveling on the horizontal fixtures on your roof, but the edge seams should get non self-leveling sealant. Third never use silicone sealant on an RV roof or any of the fixtures. Silicone is incompatible with RV roof sealants, and if it has to be replaced, the new sealant won’t stick to it.
Editor’s note: RV roof cleaners and sealants are available at Amazon.com.