100% silicone caulk will have no detrimental effect on rubber. Silicone lubricants are used all the time to seal and lubricate rubber “O” rings and gaskets. I would recommend sealing the rubber to the pipe but not to the roof.

If the boots are installed properly they do not need to be caulked unless it is a metal roof.

Good info from both. Thanks for the quick responses.

There is only one place on a roof that you should ever need to use a "caulk" that is the last piece of ridge cap that you have to face nail.

Caulking or 100% scilicone does not last the life of the roof and should not be used. what you are refering too is a salesman way of saying that we go out of our way to do a great job for you!

Then again this is just my opion

Do rubber boots last the life or the roof? One of the roofers told me that most of the time when he has a leaking roof, the problem is with an old rubber boot that has shrunk.
Comments?

I have recently removed some that were put on roofs in the early 80's that were in good shape.

Maybe what your contractor was refering to was they were installed inproperly.

most of the leaks that I encounter are form chimney flashings where the flasing and the counter flashing were fastned together and the could not move when the chinmey shifted.

If your going thru the bidding process, be very careful of any roofing contractor that wants money up front. There is no reason why one would ever need money before the job is started!

If you have any other questions contact me at leecooperroofing@cs.com or leeyohe322@cs.com

shingle monkey, thanks for the good advice. Nobody has asked for up front money. I think all 3 I've talked to are basically honest. I just want to get all details right.
Thanks again to all posters.