I have a roof that is approximately 250 square feet that is going to be realtively flat. There will be about a 6" slope running over 12' (width) for approximately 21'(length). What would be the best way to seal this that would last and not leak? Any assistance would be appreciated. The decking is going to be on 2X8 spaced 12" on center with 3/4" OSB.

Hi all- I'm on the board of a 22 unit self managed condo. We have a 4 year old rubber roof (part of a gut rehab) that leaked into a few top floor units after some really heavy rains. The installer came out and noted that some water got past the flashing and underneath the membrane, then travelled into the leaky units. He claims this is because the masonry and limestone caps got saturated and that's how the water got past the flashing. I don't doubt his claim, but we're looking to resolve the situation so that we don't experience more water damage in the future. The drainage seems to be working fine, though I haven't seen it from the roof during really rainy weather. No offense intended with this, but if not sealing the masonry comprimises the roof as a system, shouldn't that still be part of the roofer's installation? I.E. if we had a chimney that leaked because water got past the flashing, who should we call- a mason, or a roofer? Finally, is there a best way to seal the masonry and limestone? How long should such a sealant last? Thanks very much!