A dormer is a window that is typically set vertically on a sloping roof, appearing as "the eyes" of a dwelling. The dormer has its own roof, which may be flat, arched, hipped, pointed, or ornamented. Dormer windows may be built into the roof or a wall and they come in many shapes and sizes. Dormers were first used in French and British architecture in the 1600s as a way to add light to a home.
The kind of roof on the dormer may complement the larger roof or other architectural details of the house. Dormers can add beauty and curb appeal to your home, but you should carefully consider when and where to add them so they do not look out of place on your house.
Read on for the history and types of roof dormers seen in various architectural styles, as well as examples of dormers from different architectural periods throughout history.
Dormer Meaning and History
The word "dormer" comes from the same root as the word "dormitory," both coming from the Latin word dormitorium, which means "a place for sleeping. Often, dormers are utilized in attics are often converted, with a dormer and window for cross-ventilation to the space.
From the outside, a dormer is featured in many diverse house styles. Neo-Colonial, Colonial Revival, Stick, Chateauesque, Second Empire, and American Foursquare all generally include a dormer in their designs. Also, a dormer can give a horizontally-oriented house a sense of height.
When designed correctly, a dormer can accentuate the architectural features in the body of the house—Victorian scrollwork, pediments, and even window likeness and symmetry can be enhanced by a dormer with similar detailing.
Why Add a Dormer?
Dormers can have exterior and interior beauty and appeal with either a cohesive look with other windows or a look all their own, including charming glass patterns and shapes.
On the inside, what may be a dark attic space can become habitable with a dormer window in the roof that opens for additional ventilation. A dormer can also create space for an attic bathroom either for a primary suite or for an additional bathroom in the house.
Besides additional space for a home, natural light and ventilation can make interiors more inviting and healthier. If you're planning on installing a dormer in your home, call a window specialist and master carpenter instead of a roofer.
Types of Dormers
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Gable Dormers
A gable dormer has a peaked top that slopes down on two sides. Gable dormers were very popular in the Cape Cod-style home designs of America's midcentury building boom.
The simple dormers were added to the home's gable roof to add light, air, space, and symmetry to the home. You may also see a flared gable roof dormer where the dormer roof flares out for shade over the window.
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Shed Roof Dormers
A shed dormer is a dormer that has the same pitch as the roof of the house and includes windows in its narrow or elongated width. Shed dormers are common in Craftsman-style homes and bungalows.
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Steep Roof Shed Dormer
A steep roof shed dormer is one set so completely into a roof that it is practically flush with the roof itself. This gives you the ability to have windows within a steep space, such as an attic, without breaking the roof line dramatically or resorting to skylights.
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Extended Shed Dormers
An extended shed dormer is a shed dormer that extends nearly the full width of a house. This type of shed dormer adds a substantial amount of interior space without changing the footprint of the home. This type of dormer frequently emerged in the 1960s and remains a popular architectural style.
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Flat Roof Dormers
A flat roof dormer is a type of shed roof dormer with a more modern look thanks to a flat roof that has a slightly angle for water runoff. Here a postmodern architect added this traditional architectural detailing but with a twist.
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Hipped Roof Dormers
The hipped roof dormer is an elegant style that differs from the gable or shed dormer. It often mimics the lines of a home's hipped roof. A hipped roof has four sloping sides that come together in a peak, rather than a gable which has just two sloping sides.
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Arched Top Dormers
The arched top dormer is an iconic element in British cottage architecture. These arched windows bring in more light than space into the home since they sit low on a roof.
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Eyebrow Dormer
An eyebrow dormer is a curved dormer that appears to rise above the window like an eyebrow. These eyebrow dormer windows seem to make this home come alive.
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Mansard Roof Dormers
Mansard dormers are ornately designed dormers that were often seen on Second Empire-style homes. French architect François Mansart (1598–1666) modified the gambrel roof by making the sides steeper and inserting windows. Mansard roofs are some of the earliest examples of dormer windows.
Modern buildings with Mansard roofs usually have dormers—sometimes both wall dormers (through the cornice) and roof dormers. For example, the regal Biltmore Estate in Asheville, North Carolina exemplifies the 19th-century Mansard roof dormer on a chateau-style estate home.
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Through-The-Cornice Dormers
Through-the-cornice dormers are a complex design that is built straight up through the cornice or the roof's edge, rather than the common dormer that is built above the roof line. These "through-the-cornice" dormers serve as a continuation of the wall above the roof eaves.
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Nantucket Dormer
A Nantucket dormer is an iconic style often seen on its namesake island, Nantucket. It consists of two gable dormers flanking a flat shed dormer.
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Recessed Dormer
A recessed dormer is set into a roof rather than protruding out from it. It has a small landing outside the window before the roof line begins again. This typically is a deep dormer that allows for more square footage within the dormer.
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Reverse Dormer
A reverse dormer is inverted into the roof rather than sticking out from the roof. You'll often see this type of dormer used for patio or garden space.
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False Dormer
A false dormer is exactly what it sounds like—a false dormer! It's a faux window that pops out of a roof to add detail or symmetry, but it is not actually functional if you're within the house.
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Prefab Dormers
Adding a prefabricated dormer to an existing home is another option. Though it entails removing part of your roof, installing a prefab dormer may make the project go much faster. This type of dormer likely requires a plan and a permit since it entails home modification.
Cost to Install a Dormer
The cost to install a dormer can vary greatly depending on the style, the home's architecture, and the complexity of the design. Average costs can range from $2,500 to $30,000, though the average is typically $12,000, with a cost per square foot of $115.
It's recommended that you always consult a professional before installing a dormer since changes to your home that involve the roof need to be done carefully to prevent leaks and insulation problems. Depending on your roof's material and design, there may be more complexities in how the project should be planned and executed. Labor and materials are critical costs to consider.
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What is a gable vs. a dormer?
A gable roof has two sides that form a peak at the top. A dormer can protrude through a gable roof.
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Do you need planning permission for a dormer?
You will probably need a permit to add a dormer to your home. Always check with your local town hall to find out what permissions you may or may not need for a project like this where you are modifying your home. Sometimes the town planning department needs to make sure the dormer doesn't exceed height restrictions, for example.
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What are the pros and cons of dormers?
Dormers can add light, liveable space, and air circulation to upstairs rooms and attic spaces, while also adding a charming look to your home. But there are a few cons.
Dormers can be expensive to install and, if square footage is your number one concern, you will lose some space to a dormer.