I’m in the process of mounting some roof ventilation (Maxxair fan) on my van, and I’m struggling to figure out exactly which sealant to go with. Everywhere I look I am getting different advice; there are adhesive strips, sika flex, lap sealants, butyl tape, and various primers to go with everything. It is killing me.
What I have is a plastic frame that needs to be mounted on a metal roof. The opening of the roof is already primed with metal primer (needed anyway after exposing the metal when cutting the hole).
I bought Sika flex-554 as that seemed to be the perfect fit, and I did a little test on the plastic frame just to be sure it would adhere properly. I cleaned the surface properly before applying, and I left it to dry for almost 3 complete days without touching it. In the end I was still able to relatively easily peel it off with my fingers. I don’t feel confident this would hold for very long. Now i’m in the process of figuring out what else to try, and I figured I might as well ask for some advice.
Is Sika flex the way to go? If so, what is the most appropriate? I have also been looking at 449, but in the end it seems very similar to 554 (which i already tried) on paper.
Do I need a primer for the plastic? Is that perhaps why it didn’t stick good enough?
Can/Should I apply some Dicor lap sealant around the edges after the sika flex has dried? Does sika flex and Dicor go well together? Does this make sense?