The dormer that came later
A lot of the attic space in this valley was made habitable long after the house was built, and that work brought dormers with it. Every dormer added is two more valleys, two more wall junctions and a small roof of its own on a plane that used to be plain.
- 1 The ridge cap. On metal it is a separate piece with closures under it. Blown snow finds the joint that was never closed.
- 2 The seams. A standing-seam roof lives at its seams and clips, not at its surface. The panel outlasts what holds it.
- 3 The valley. One channel taking what two slopes shed — and on the north side, holding snow long after the field is clear.
- 4 Where the ell meets the wall. A lower wing dying into the main house. Two roofs, one wall, and nobody sure whose seam it is.
- 5 The fasteners. Exposed screws through the panel, each with a rubber washer. The washers age; the screws work loose.
- 6 The eave. Drip edge, gutter, and the question every metal roof asks: where does a slab of snow go when it lets go?
A valley is a channel, not a joint
Where two slopes meet, everything both of them shed goes down one line. That line carries several times the water of the field around it, and in this climate it holds snow long after the open slope has cleared — particularly on a north face, where it can stay packed for weeks.
Which is why valleys are lined rather than simply covered, and why the lining is not the place to save money.
Why an added dormer is worse than an original one
A dormer framed with the house sits in a roof designed around it. One cut into an existing roof is fitted to what was already there, often by a carpenter rather than a roofer, and often with the covering worked around it afterwards.
The tells are visible from the ground if you know to look: a valley that dies into a wall instead of running out onto the roof below, a dormer cheek that meets the main slope with sealant rather than step flashing, a gutter that was never extended past the new work.
What a replacement should fix rather than repeat
A tear-off is the one moment when these can be corrected properly, because everything is open. Step flashing along the cheeks, replaced rather than reused. The valley lined and run out, not stopped short. And the ventilation of the room below looked at, because a finished attic that was never given intake and exhaust is the reason ice forms at that eave every year.
If the quote says the dormers will be reflashed as found, ask what "as found" means. It usually means the same detail that failed.