since you can't get good coal tar pitch, & a good tar co. would want too much to do it would pass on a small roof, you're left w/ jack-legs who will screw it up! Many things can go wrong & you'll never know. not enough layers mopped down, the tar under heated, or worse over heated ( do you want to stand out there w/ a thermometer? ) go w/ torch down, or check out ge single ply rubber ( pretty cool, but i think only for flat roof, if one single plane they could probably do it!)