A Practical Prefab Dormer, Images 21-28

Ridge: Next we laid out the ridge board and secured it between a second pair of rafters at the back of the dormer.

Ridge: We placed a straightedge across the front face of the dormer to make sure there was no deflection in the hinge joint at the top plate.

Ridge: We spiked the ridge to the floor at its back end, so that the whole dormer assembly was stiffly braced.

Subfascia: After filling in the rest of the rafters, we ran 2x4 ceiling joists across the plates, extending them a few inches to catch a 2x6 subfascia.

Subfascia: For speed we ran the subfascia long, then trimmed it at the gable; we held up its angled end on a scrap of 3/4-inch sheathing, so the roofer would be able to slide his shingles into the gap.

Scribing the Valleys: We now had a pattern in place — the gable sheathing — from which we could accurately project the curve of the roof from front to back. The top of the 2x6 subfascia defined the bottom edge; the flare would smoothly transition into the straight 2x6 rafters at its top. The first step in the process was to cut plates for the valleys out of 2x12 stock and position these between the subfascia and the ridge.

Scribing the Valleys: These plates provided a target for projecting the flare from the gable, which we did by using various pieces of framing lumber, depending on the thickness and angle required.

Scribing the Valleys: With the curving valley thus scribed on the 2x12 plates, we pulled them out, cut the curved profile, then reinstalled the plates permanently at the ends of the jack rafters and blocking.

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