We started by framing in the dormer on the existing roof.
Once the dormer was framed in, we added wood decking to it. Then we used Owens Corning Pro Armor synthetic underlayment to prevent moisture buildup.
Once the dormer was built, we were able to match the exact shingles from the existing roof to perfectly blend the old and new portions of the roof. We also matched the vinyl siding of the house for the front of the dormer.