Flat dormers do not have pointed gables located on top of the window. Commonly called a "shed dormer," this style of dormer is constructed into the roof slope and can extend the headroom in a second-story room. Installing windows into the dormer allows natural light to penetrate the room. Sometimes, the flat dormer can be placed in the roof overlooking the living room, allowing natural light to enter the main living area and opening up the ceiling.
An arched dormer is still installed into the roof slope, but the roof line above the dormer is arched in a semicircle instead of flat or pointed. These types of dormers can be difficult to install unless the wood is already formed into a designed arch. Many arched dormers have a brick or stone face because it is easier to form stone into a semicircle than it is to bend wood to fit the semicircle arch.
The pointed dormer design is the most common dormer and gable. Many single-story homes have gables located on the end of the main roof, but have pointed dormers installed along the front face of the roof. Each dormer has a gable end, and generally more than one dormer is installed into the roof surface. The pointed dormer and gable design is easier to install by cutting an opening into the roof. The design allows natural light into the rooms below, but has no other practical purpose other than cosmetic.
Ventilation dormers do not have windows located in the front of dormer. Instead, the dormer has a small vent to allow air to flow into the roof, providing more ventilation to the underside of the roof. These types of dormers are small and only extend a short distance out of the front of the roof. Gable ends are located above the dormer.