What Is a Gable Dormer?

Written by joseph benincase
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What Is a Gable Dormer?
Gable dormers peak in a triangular shape. (gable end image by Rob Hill from Fotolia.com)

A dormer is a component of a house or other building that extends outward from the plane of a roof's surface. A gable is a part of the structure that encloses, in a triangular shape, a protruding structural element. Gabled dormers are structural elements with triangular peaked, sloping roofs. Dormers are useful for creating space in a roof's structure, particularly as an attic.


In classic Greek and Roman architecture, the word "tympanum" refers to a triangular space forming the centre of a pediment, typically for decoration. This type of dormer was out of fashion for sometime until, in the 17th century, French architect Francois Mansart developed a similar style and updated it to a modern application. Today, gable dormers are still used for many houses in the United States.


Dormers allow for extra attic and bedroom space in homes. Gable dormers may add headroom in a bedroom and provide wall space for additional windows. They allow for ventilation installation. Gable dormers are viewed largely as aesthetic decorations.


The word "gabled" refers to houses with peaked, sloping roofs. The main identifying element of a gable dormer is the triangular shape created by the pediment. They extend past the roofline of the building, and with two triangular slopes meet at a peak. A hipped dormer, although having similar functions, inclines from the roof along with its sides. This creates a vertical rectangular shape rather than a triangular shape.


One of the most famous houses with gable dormers is the House of Seven Gables in Salem, Massachusetts. Its design maximises space for additional rooms, windows and attics. Many Cape Cod-style homes up to the mid-20th century are known for their gable dormers. The triangular shape of the feature is common for Gothic, Colonial Revival, Tudor and Georgian homes.

Other Names

Gable dormers are sometimes referred to as "tympanums." They are also referred to as "pediment dormers," "dog house dormers" and "A-shaped dormers."

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