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Dormer windows are most associated with Colonial and Greek Revival architecture, but it’s common to see them on any home with a sloped roof. Like their architectural predecessor, the lucarne, they bring light and airflow into vaulted upper levels of a house. There are several styles of dormer windows. Below, we’ll explain these options as well as the cost and installation process.
What Are Dormer Windows?
Dormer windows became popular in 16th century Britain. Their name is derived from the French word “dormeor,” which means “sleeping room.” They provided a way to get natural light and air into attics and lofts that were used for sleeping but didn’t allow for traditional windows due to steep vaulted ceilings. Though dormer windows can still serve these purposes today, they’re usually more of an aesthetic preference.
Dormer Windows Functionality
Dormer windows are most commonly found on a pitched extension of a front-facing sloped roof. They can be operable or inoperable. Operable windows are most commonly designed to raise upward, though some can tilt inward. They add extra space on the interior, creating one or more nooks for window seats, reading areas, or storage.
From an outside perspective, dormer windows help break up a roof and give a house the appearance of added height. They can accentuate the home’s architectural details and finish the facade the way that eyes do a face.
Dormer Window Styles
Dormer window styles are defined by the roof type above the window. Below are some of the more common types of dormer windows:
- Blind dormer: Blind dormers—or false dormers—are for appearance only. They look like ordinary dormer windows from the outside, but they’re only attached to the facade. Internally, there is no window.
- Bonnet dormer: Bonnet dormers have a curved roof and vertical walls on each side of the window.
- Eyebrow dormer: This style of dormer has a gently curved top and no additional wall space on either side.
- Flat dormer: Flat dormers are named for their flat roofs. These are often found on the front and back of a house.
- Gable dormer: Gable dormers are the most common. They have a triangular roof over the window, which is positioned symmetrically under the roof’s pitch.
- Gambrel dormer: This dormer style also has a pitched roof but descends into two steeper roof slopes on the sides, giving the window a barn-like appearance.
- Hip dormer: A hip dormer has three roof planes, one on each side and one in front. All planes slope upward and meet at a point.
- Lucarne dormer: Lucarne dormers pay homage to those found on Gothic cathedrals, featuring gable roofs and a tall, narrow design.
- Shed dormer: Shed dormers have just one roof plane that slopes the same direction as the main roof but with a much shallower pitch.
- Wall dormer: Wall dormers can have any style of roof pitch. What distinguishes them is that they’re flush with the front of a home’s facade instead of the bottom of the window sitting on top of the roof.
The roof pitch of dormer windows traditionally follows the home’s primary roof, though it’s becoming more common to vary roof lines as long as dormers are complementary to the overall facade.
Dormer Window Installation
For new-construction homes, a contractor will construct the dormer frame at the same time as the primary roof structure. Sheathing must be applied to the outside dormer walls and over the rafters of the main roof. Vapor barrier wrap is installed over the sheathing on vertical walls. The window can then be installed, followed by the roof’s shingles. After completing the dormer’s exterior, its interior can be finished to match the rest of the room.
If you want to add dormer windows to an existing house, you’ll need approval from your township or county since dormer window installation is considered a major structural change. If approved, a licensed roofing contractor and window specialist can install the dormer window. You can opt for a false dormer window that gives the appearance without as much invasive construction if you prefer.
Dormer Window Cost
Based on 2022 research by HomeAdvisor, the average cost to install a dormer window is $12,000. This price fluctuates based on dormer size and style. Estimate roughly $115 per square foot for the project. Eyebrow dormers, which are smaller than more traditional gable-style dormers, may cost closer to $4,000, while adding a large flat dormer can cost upwards of $25,000. Keep this in mind if you’re installing multiple dormers.
Should You Install Dormer Windows in Your Home?
Dormer windows can increase natural light and air circulation and add visual interest to your house. It’s important to note that since dormer windows penetrate your main roof, they increase the chance of developing a leak. This is why it’s important to hire a licensed, experienced contractor to perform the installation.
If your house has a dull or awkward roof line, adding dormer windows can help balance the look. Make sure to hire reputable professionals to perform the work, and choose quality windows with a good warranty. See our guide to the best window brands to start your search.
Dormer Windows FAQ
What’s the purpose of dormer windows?
Dormer windows were and still are used to allow sunlight and air into an upper-level vaulted room, such as an attic.
What are the benefits of dormers?
The main benefit of dormers is that they allow you to add windows to rooms with sloped roofs not suitable for traditional windows. They also increase natural light, interior space, and curb appeal.
What is the difference between a dormer and a gable?
A traditional gable window is flush with the wall of a house. A dormer window protrudes from a house’s roof.
What are the disadvantages of dormer windows?
The primary disadvantage of dormer windows is the risk of a roof leak. A qualified contractor should install flashing that prevents this, but dormers penetrate your roof, so there’s still a chance a leak could occur.