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. The finished costs are to be used with finished upper floors (be sure to include the floor area of the dormer in your total calculation) or in vaulted or cathedral ceilings, to allow more light. Dormer cost includes the dormer framing; exterior and interior 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.