Our existing roof has an overhang of about 30mm over the gutter. The roof is an extension on the original house, with a sloped tile roof, running onto a corrugated iron roof, which then flows into the gutter. I recently replaced part of the fascia, which is two pieces. The lower section is 180mm high, and the top piece is 65mm High. The lower piece has been replaced at some stage and is still the pink primer that was on it when installed. The upper piece was completely rotten, with the gutter hanging off. I needed a quickish repair, so I replaced the upper section only. I plan to replace both with a one piece fascia, but before I do, I need to understand the gutter installation better. At the moment, with a 30mm overhang, water appears to get behind the gutter, and run down the fascia in a few spots. From what I've read overhang should be 50mm. Will the increased overhang allow water to flow into the gutter better? It seems the water is able to flow uphill slightly to get to the fascia, and also the last batten, and to some extent the ends of the rafters. Do gutters normally get sealed against the fascia to prevent water getting behind it? at the time this was happening I had a look and the gutters weren't overflowing, it was just the water wasn't dripping from the ends of the roof sheets.