I have a standalone garage built into the side of the hill. On top is a rubber roof that appears to be in decent shape. However, there is a gutter around the edges that is not sealed to the roof. Obviously I need to clean off the roof and under the flashing/gutter edge. Do I need to take it all off and redo it? Or can I just clean under and seal it with something? What do I use? Roofing tar?
You can seal that gap quite effectively with a product called Eternabond - it's very popular in the RV world to seal roof seams, vents, windows, etc. Simple to work with (it's basically like a roll of tape), waterproof and very durable.
After realizing I had screw holes in my rubber and some other problems, I had to do a total roof replacement. So, sealing this gap wasn't my solution.