In most cases if the shingles go past the drip edge about 3 4 of an inch the shingle edge will break the surface tension unless your roof has a shallow pitch then the water will reach the drip edge and if drip edge is tight to the facia board it will run down the fascia so as added insurance leave space between the fascia and drip edge.
Gap between roof sheathing and fascia.
This material should have extended all the way to the bottom ends of the rafter joists where the roof deck meets the fascia board basically the area where the gutters are hung.
I think that this practice differs by region though.
Slowly move down the joint to apply a steady bead of caulk into.
As a result the drainage improves water flow and protects the roof from potential water damage.
Smooth the caulk bead with your finger and begin caulking the joint between the fascia board and the soffit also known as the eave.
The worst part looks about 10 long but i can t see the whole roof since it is too high.
Then i do a metal drip edge to cover it all.
Unfortunately in most homes this is not the case.
On my shed my sheathing does not protrude actually how both my house and shed are done is a 1 x 6 house 1 x4 shed fascia is installed to end of rafters then 1 x 1 1 2 is tacked onto the fascia at the top.
The roof sheathing comes down and ends on top of the 1 x fascia.
This is a pretty expensive home.
Why is a drip edge important.
The roof decking is left slightly shorter than the rafter ends creating a gap between the roof and the gutter.
Builder looked at it and said he d have one of his siding guys come out and install flashing to fill the gap.
The staining on the fascia suggests that this bat problem has been going on for a while.
The gap between the roof sheathing and the fascia may be small but it was all the space that bats needed to get into the attic of this house in atlanta.
I doubt that that is the root of the problem though.