A puzzle: Can you figure it out?

This photo is from a very nice home at Point Roberts. The roof had been installed within the last few years and the shingles were still in good shape. It was 3-tab composition material, neatly installed and with a uniform overlap so the self-sealing tabs lined up correctly on each course at the upper and lower roof. Standard felts were in place underneath. So, with all of this done so right, what could have been so wrong that the buyer demanded major changes to the roof prior to closing? See how you do and please let us know below. The answer is below the photo.

 Answer: The lower roof was fine, and sloped at 3/12. The upper roof was so low sloped, barely 1/12, that it could almost be considered a flat roof. 3-tab shingles are not designed for such a low sloped application. 3/12 slope is as low as they go, with some people suggesting no lower than 4/12. Manufacturers would not stand behind this installation and they are more vulnerable to leak as they wear. The problem is, these shinges are designed for slopes and work like an umbrella -- they keep the water running down off the roof. If it is able to collect, and pool, it will work up under the material. Granted, it is standard on many mobile homes to use 3-tab with slopes between 2/12 and 3/12, which is not great but how they do it. It does work for a time, although that marginal application shortens the life of the roof and leaks are more likely; everyone has heard that story of mobile homes having frequent roof leaks -- that is one reason for it. In fact, if the slope is steeper, it is amazing just how bad a roof can be and still shed the water. In this situation in the photo, the upper roof was, properly so, changed to a standard coating for a flat or low sloped roof. This person chose torch down, although EPDM and some other options were available. I hope posts such as this give you some insight into all the different things home inspectors have to remember.

Thanks for looking,

Steven L. Smith

Bellingham Washington Home Inspector