large leaking tar flat roof
I own a large, old (late 1800's), mixed use building with a flat roof in upstate NY. The roof has been leaking to the point where I definately would like to do something about it this summer. The roof is in two large sections, roughly 50x65 and 65x65, so approx. 7200 sq ft. The roof is "flat" and it is what I am pretty sure is tar. Seams of what I imagine is tar paper are starting to show through.
I started doing my own research to figure out how I was going to attack this. I'm rapidly coming to the conclusion that I will need help. While I have done all the interior remodeling (framing, plumbing, electrical, etc.), I have never done any roofing work.
My first thought was to go over the existing roof with wood and a fully-adhered rubber roof. My reading leads me to believe this may be a bad idea due to trapping moisture? ripping the roof off seems a monster project. My rough investigation gave me a cost of $18,000 and that was doing it myself with 3-4 man help.
I may re-tar, but such a short lived solution, anyone have any thoughts? and possibly a product/application tips?
any and all thoughts are appreciated.