went up on the roof today to clean it (manufacturer says it is walkable) and found a hole in the membrane. only about half an inch cut, don't know if a limb fell on it or what but the OSB was just starting to swell from moisture. used Eternabond so should be good as new, water damage was minamal, not enough to worry about. glad i found it when i did. checking the roof should be right up there with checking the air in your tires. IMO anyway.