Sealing roof mounted items with silicone vs Dichor

[H3Jim]

Last year I installed various things on my roof using screws and bolts.  To seal, I put goop underneath and all around the edge, and in the hole itself.  I used three different types of sealant, depending on when I did it and what I had to use.

I used silicone sealant to mount a bracket for my roof mounted awning, the best home depot had, longest lasting blah blah blah. 
I used some butyl tape for my air horns and sewer vent pipe.
I installed the rest of the awning brackets, the solar panels and my Fantastic vents using Dicor.

I just looked up there, and all the silicone has peeled and become unstuck.  I think where it is sandwiched between plates, or fills a screw hole it is still water tight, but any on the surface is coming off in sheets or just flapping around.

Dicor is un-fazed by being up on my roof for a year.  Great stuff.

The butyl tape is also holding up nicely. 

So be aware that silicone is not the best sealant for your roof.  I was sold on Dicor before as several people have told me that it is bulletproof (or at least waterproof) and I will not ever have leaks with it, but I just got some firsthand experience. And I wanted to pass this on to the board.

[Dallas]

Jim,

I've been telling people for years that silicone is not the best sealer, especially for smooth surfaces.

One problem it has is that it doesn't really stick to the surface, unless the surface is somewhat roughed up, another problem is that silicone caulk WILL NOT STICK TO SILICONE CAULK!.
I've had great luck using Dichor or Butyl tape. I have better luck using Polyurethane caulk especially for sealing around windows and between metal sheets.

Dallas

[gus]

What the heck is Dichor?? When I google it I get glass and spa chemical?

[Dallas]

Sorry Gus, It's Dicor, not Dichor.  I mispelt it. 

http://www.dicor.com/roofmaintenance.html

[niles500]

I've always had good luck when using sheet metal screws, dipping the threads in the nasty sticky black butyl that comes in caulking tubes - as you drive the screw the butyl seals around the threads and backs up under the screw head - HTH

[jjrbus]

Anything other than butyl rubber tape for attaching anything to the outside of the bus is absolute last choice. The new hi-tech adhesive sealers ie 3M 5200, Sikaflex etc do not come off without a fight. I'm not saying don't use them, just don't use them on anything you may want or have to take off the bus someday.
             HTH Jim

[DavidInWilmNC]

I don't find much info as to what Dicor or which product you're using.  I've found that polyurethane sealer is wonderful for things that you don't want to leak or to be removable.  I believe most of the Sika Flex products are polyurethane, btw.  I use the black stuff in a tube from Lowe's.  It's sold as flashing sealer, but has worked great everywhere I've used it.  It's nasty stuff if one gets it on clothes or hands so use disposable gloves.  I've found that it works much better than silicone.  I also use butyl tape for things like roof vents that will need to be removed at some point in the future. 

David