A projection from a sloping roof to provide more headroom under the roof, allowing the installation of dormer windows. The dormer itself has a gable-style roof. Enter the length of the projected face in linear feet. Use the unfinished cost for unfinished upper floors and for unfinished attics. Dormer cost includes the dormer framing; exterior finish, windows, additional roof framing and bracing, flashing, etc. Costs for small dormers will usually be more expensive per linear foot than larger or longer dormers. For example, a small dormer in a fair quality residence may require good-quality costs for pricing purposes.