The roof on Kevin's house was flat, and although built well enough to have lasted more than 100 years, it still collected puddles of water in the rainy season. It also leaked.

Without a significant slope, a flat roof is more vulnerable to water damage. A waterproof membrane prevents leaks but needs periodic maintenance. The post Flat Roof Repair and Maintenance appeared ...

It is a tar-paper roof, applied by professionals over a flat wood surface. They had no idea how to add a slope after I said the roof was gathering several inches of water after heavy rainfalls.