The Difference Between Dormer and Gable Windows

Dormer Description

• A dormer extends out from the diagonal slope of a roof. Dormer sizes can vary, from just wide enough for a window to large enough to accommodate two windows. Although dormers usually have at least one window, windows are not a required feature of dormers. Windows can be standard square or rectangle shapes, or they might be half or full circles.

Dormer Purpose

• Dormers serve two purposes when added to a roof line. They increase living space in interior rooms, especially when converting attic space beneath pitched ceilings. Adding dormers provides a horizontal living area that extends out from the triangular-shaped ceiling. Additionally, dormers with windows bring in natural light to make room interiors more pleasant and livable. Sometimes a dormer holds an attic vent and not a window. These dormers are “false dormers” and add style but not living space or light.

Common Dormer Styles

• Dormers come in several different shapes. A shed dormer has one flat roof with an eave line parallel to the roof line. A hipped dormer has three planes that slope out from the center. An eyebrow dormer curves in a half-circle shape -- often an ideal shape for a curved window. Gabled dormers have a triangular roof.

Gable Roof

• A gable roof -- whether on a dormer or on a building -- has a triangular shape where the two roof planes meet in the center. One of the most common roof designs, a gabled roof has the benefit of allowing moisture to run off easily. A dormer with a gable roof will have a standard triangular roof that sits above the structure.

Gable Windows

• Because the gable is a feature of the roof design, windows are not usually included in the gable design unless they follow the triangular gable shape of the roof line. A gabled dormer typically has a window on the front. Although the most common window shape is square or rectangular, some gabled dormer windows are triangles beneath the triangular shape of the gabled roof. The triangular windows might be one large window or two smaller windows that make up the triangle shape.