Originally Posted by KeepItSimpleStupid
The drip edge has a verticle section. That is available in various lenghts from 1" to maybe 6" long. It also has a fixed section that goes under the shingles and the length doesn't matter.
A drip edge is a little fancier than a 90 deg bend, but for all intents and purposes for this discusson, assume that is what it is. About 4" that goes under the shingle and some distance X that folds over the edge.
Assume X is 1". Roof thickness is 5/8" of an inch. 1" minus 5/8 = 3/8". Thus 3/8 of an inch of the drip edge extends below the edge of the roof. The top of the gutter, then buts up against this. This puts the gutter 3/8" of an inch below the bottom edge of the roof.
If that overhand was 2", the gutter would be 2" minus 5/8" or 1 and 3/8. In this case the gutter would be 1 and 3/8 of an inch below the bottom edge of the roof and that would not look good at all.
Make sense?
I'd have to measure what the stuff I used last year was.
Aside:
The tar paper or ice and water shield goes ON TOP OF the drip edge portion that goes on top of the roof.
The drip edge actually extends the roof line by about 1/4", but it mounts flush against the thichness of the plywood. It ten goes down X distance and has a small outward bend to it, so water is directed away, rather than under the roof.