We recently finished a U-shaped 11x18’ addition. The roof is rubber, appears flat but actually has slight pitch/angle which carries water into one gutter along the bottom of the U (the 18’ width) with downspouts on both ends. Strangely, the gutter ends about one inch BEFORE the end of the width of the addition. One side of the gutter seems to catch most of the roof water but the other side does not. As a result, water sprays off the side of the addition, doesn’t make it into the gutter and forms a large puddle next to the bottom of the downspout. We have mentioned repeatedly that we believe the gutter was cut too short and should have extended at least an inch BEYOND the roof line. After much pestering, our contractor agreed to try to fix by installing (humble looking: 6-8” long and less than 2” high) rain diverters on both ends of the roof that empty into the gutter, but they aren’t effective – water still drips off the side and forms a puddle. Is the only solution to tear down the current gutter and install a wider gutter that would better catch the water? I have searched for terms like “gutter extenders” but cannot find possible solutions. While the contractor’s work is still under warranty, we do not trust him at this point so are seeking outside feedback and might even consider having someone else correct it the right way.