Thursday, April 25, 2019

Up on the r-o-o-o-o-f

Back when I took the big leap and cut a 14-inch hole in the Rolling Steel Tent’s roof so I could install a vent fan, the conventional wisdom included sealing the screw holes and hood edges with the same stuff the RV industry used. Dicor self-leveling sealant. Or Dyco C-10 self-leveling sealant. I chose C-10 because someone on a forum said something bad about Dicor.


A couple of years later the ravages of UV rays had cause the C-10 to dry and crack—which was what Dicor had been accused of doing. There had been no leaks, but better safe than sorry. So I applied another coat of C-10. And repeated the process the next year.

When it was time to refresh the sealant again, a friend gave me a tube of Dicor. Oh, a comparison test. Science! Eh, same results.

A few months ago, another forum guy highly recommended 3M 4200 Marine Adhesive/Sealant. Superior UV resistance, he said. Okay.

Unlike self-leveling sealant, 3M 4200 is thick and gummy, so it’s harder to apply elegantly—especially when you’re on a ladder, stretching to the middle of the roof. But I used an old business card to spread the adhesive/sealant around and cover all the critical points. We’ll see how things are next year.



  1. Last year I resealed a bunch of seams and it looks like a rookie job. Then I found a utube video showing how an RV dealer does the job. Their seams look beautiful. The trick, they said, was the use of mineral spirits. I tried it and can confirm it works well. Clean before applying with mineral spirits and the follow the application with a finger wetted with the spirits. The soaked rag from the first part of the process works to clean your finger on as you go. Another pro tip was to work in short sections so it doesn't skin over before you dressed it up.

  2. I read on a forum post that you can prevent UV damage by covering up your sealant with aluminum tape. I think I'll go try that. Ming