I used to worry every time I installed a skylight. Even with the best installation detailing, I could still expect a storm to hit from just the right direction and drive water behind the flashing. When I discovered peel-and-stick membranes, my worrying days ended. Now I follow a series of simple steps that hasn’t failed in more than 15 years’ worth of installations. The key to success is integrating the membrane and the flashings with the shingles to direct water back to the surface of the roof. Although the project shown here is a retrofit, I would flash it the same way on a new home.