I'm siding around a couple of Dormers. When I install the J-Channel on the bottom of the sides of a dormer along the sloped roof How low should the J-Channel be? Can It touch the shingles? I'd have to nail the J-Channel about 1 inch up on the step flashing if it does touch. Are other steps typically taken, other than the housewrap, to protect the wall of the dormer from water?

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You're right that nailing so low is a concern. Typically I'd leave at least an inch between the shingles and the channel. If you use color-coordinating step flashing this isn't an aesthetic concern. You can also overlay rubberized window flashing tape on the step flashing to seal nail punctures better.

You don't say where you are, but I'd worry about melting snow leaking through low punctures in the flashing, or flow and splash from heavy rain.

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