Roof sealant question

BrianT · June 25, 2016

My rubber roof seams are getting pretty old and cracked. I need to go over them with Dicor. But I have a question.

Are you supposed to dig out the old stuff before applying the new sealant?

The reason I ask is because of an experience I had a few years back. I had a leak somewhere around the skylight just over the bed. I tried laying new sealant over what was there 2 or 3 times. Still leaked. I got frustrated and scraped as much of the old stuff off as I could, cleaned with alcohol on a cloth and resealed again. It has been leak free ever since.

When I find youtube videos, they usually just show them putting a bead of sealant over what looks like a brand new RV that doesn't need a thing... it's a tv production, I guess... complete with a commercial.

Anyway, just thought I'd run it past you guys to see if I'm on the right track in my thinking.

Thanks for the input,

I'mdonewiththis forum · June 25, 2016

Yep, you found out the hard way what you need to do. Remove as much as the old stuff as possible and clean the surface with alcohol or something similar, allow it to dry and reseal. Sounds easy, but as you know the old stuff is a PITA to remove.

chirakawa · June 25, 2016

Some RV pros use this tool with a similar blade to remove old caulking.

Kirk W · June 25, 2016

The reason that you need to remove most of the old caulking is that if it has cracked enough to leak, you are not filling the leak but only trying to cover it up. If only a small area is in question and has not begun to leak, then it might work to add a bit more, but you do not want to just keep piling more and more on.

The material used is a "self leveling" caulk which means that it will flow and if you remover most of the old it can then flow down into any openings which are potential leaks and seals them before the leak begins, rather than just covering the opening up. As far as removing caulking from a roof, I have used the oscillating tools and there is no way that I would allow one to be used on an RV roof of mine, and especially not if it is EDPM. I have watched the tech remove caulking on our present RV with a metal roof and have done so myself with both metal and EDPM and I only use plastic tools on EDPM and mostly use them on aluminum. It might be possible to use the oscillating tool to remove caulking, but it will cut very quickly into roof materials if you happen to hit it. There is noting better for making holes sheet rock and plywood.

pugsly · June 26, 2016

Some RV pros use this tool with a similar blade to remove old caulking.

I've used that, but only because I have a fiberglass roof. If you have anything else I think a plastic scraper and a heat gun on a warm day is the best option.

I scraped off everything on my roof earlier this year and redid everything. Previously I had just done touch-up work, but after 10 years it was time to make a clean start.

After doing a lot of research I decided to use the ProFlexRV brushable sealant. I liked being able to tape everything off with blue painters tape and put on as many coats as I wanted. http://www.campingworld.com/shopping/item/proflex-brushable-sealant/21208

BrianT · June 26, 2016

Thanks, guys. I had a feeling...

Yes, I would think it would be easy to damage things if getting too aggressive with the tools.

Can't say I'm exactly looking forward to the job ahead but I'm pretty confident I can get 'er done.

Thanks again for the input! I appreciate it.

Kirk W · June 26, 2016

Can't say I'm exactly looking forward to the job ahead but I'm pretty confident I can get 'er done.

It really isn't too bad a job but try not to choose a really hot, sunny day and if you have the option, put the RV under a cover to provide shade for better working conditions and so that you don't have to get it all done in one day, in case of rain. Most caulking wants 24 hours before it is rained on and I prefer to give it at least 48 hours.

BrianT · June 27, 2016

I figured on doing one piece at a time. For instance, I'll probably start with one of the skylights, start to finish. Then, if I'm taking too long or need a break or it gets too hot or whatever, it's no big deal. I figure once I've done a few smaller seams, I'll be a bit more practiced for the longer runs down the sides.

Ray,IN · June 27, 2016

My experience is, a power tool helps me make a mistake___ quicker. I use the heat gun method, then clean up with mineral spirits(non-petroleum product) on a damp rag.

dartmouth01 · June 27, 2016

If you prefer to take an easier route, I would consider using eternabond to cover all the joints. I have only used it on a skylight install, but wouldnt hesitate to use it instead of Dicor for anything else. I believe others on this board have used it over every place that has been Dicor'd, with fine results.

pugsly · June 27, 2016

If you prefer to take an easier route, I would consider using eternabond to cover all the joints. I have only used it on a skylight install, but wouldnt hesitate to use it instead of Dicor for anything else. I believe others on this board have used it over every place that has been Dicor'd, with fine results.

I keep Eternabond in my bag of tricks, but more for on-the-road emergencies. If you need to patch a crack, hole, or leak "NOW" then it is an excellent choice if not the choice.