Hi, I have a 15 year old flat roof. In a few places, the felt has pulled away from the brick upstand and water is getting in. I have had 2 quotes to repair it - without replacing the whole roof, which is the best method for a proper repair? method 1 - cut away affected felt - sand and cement - prime - re-felt or method 2 - cut away affected felt - grind back mortar bed - trowel on bitumen to build up repair and use grey acropol as a secondary seal Not much in the price, I'm more interested in what will fix the problem for the next 10 years? Thanks in advance!