Q: What is the proper pitch of gutters? Do you attach the gutter over flashing or under it? - Rod Hibbard, Manitowoc, WI
A: A commonly recommended pitch for gutters is 1/4 in. every 10 ft., but the only rule is that gutters must pitch toward the drain. Water finds its own level, so even a very slight pitch will allow water to drain. However, a too-steep pitch can lead to overflows during heavy downpours.
Strip flashing prevents water from flowing behind the gutter and damaging the fascia boards, but it is not always necessary. Flashing is most important on low-pitch roofs (such as those with a 4/12 pitch) because capillary action is likely to draw the water back under the drip edge or shingle. When you install strip flashing, it must run under the drip edge or roof material and over the top edge of the gutter (see illustration above). - HANDY