A dormer is a window that is typically set vertically on a sloping roof. 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. 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, or they can end up making your house look ridiculous, so you should carefully consider when and where to add them.
Take a look a these examples of dormers from different architectural periods throughout history.
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The Eyes of a Dwelling
The dormers shown here, each having a gable roof, are from a pub called The Myddelton Arms. Located in the Medieval town of Ruthin in northern Wales, these notable and popular dormers from the 16th century are known as "the eyes of Ruthin."
For centuries, windows have been known as "the eyes" of a dwelling. Like a chimney, roof dormers are not part of the roof but stick through the roof. Some dormers, called wall dormers, stick through the edge of the roof at the cornice.
Essentially, dormers are "glazed structures," meaning they are windows. In fact, they are sometimes called lucarne, a French word for "skylight." The gable above the dormer is called the dormer head, and it is often in the shape of a pediment.
To install a dormer in your home, call a window specialist and master carpenter instead of a roofer.
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Why Add a Dormer?
Dormers can have exterior and interior beauty and appeal. On the inside, what may be dark, attic space can become habitable with a dormer window. An additional bathroom can be enlarged by a dormer tucked into a large bedroom. Besides additional space for a home, natural light and ventilation can make interiors more inviting and healthier.
From the outside, a dormer can define certain house styles—Neo-colonial and Colonial Revival, Stick Style, Chateauesque, Second Empire, and the American Foursquare are all house styles that generally include a dormer in their designs. Also, a dormer can give a horizontally-oriented house a sense of height, especially if the house is situated very close to a street. When designed correctly, a dormer can accentuate the architectural details in the body of the house—Victorian scrollwork, pediments, and even window likeness and symmetry can be enhanced by a like-minded dormer.
Avoiding the False Dormer
Like cosmetic cupolas that sit without function atop a roof, the false dormer is a growing trend, especially in new commercial real estate. In an attempt to mimic a certain hometown colonial style of architecture, dormer units are attached to the roof without breaking through the roof. False dormers may be out of proportion—either too large or too small—and look unnatural. The artificiality of planned communities like Celebration, Florida is due, in part, to this type of fake architectural detail.
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Dormer Comes From Dormitory
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." It should come as no surprise, then, that attic spaces are often converted into extra bedrooms with a dormer to cross-ventilate with a gable window. Original dormers may have been built into an older large home to accommodate live-in domestic workers.
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Besides extra sleeping quarters, the additional interior space created by a dormer took a different turn with the invention of indoor plumbing. Bathrooms require headspace for standing, and a dormer allows this height to be added above a toilet, sink, or bathtub. This allows an attic space to have a bathroom for a master suite or as an additional bathroom for the house.Continue to 5 of 16 below.
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Inside Space and Window Options
The amount of light and ventilation afforded by a dormer is a function of the imagination. The windows can match the other windows of the house, or you may make the dormer window fancier, such as with colored glass or a non-traditional shape. The windows may be fixed or they can be designed to open to allow for ventilation.
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Dormers were especially popular in the 1950s Cape Cod style home designs of America's midcentury building boom. There is nothing fancy with these additions—simple gable roof dormers functioned to add light, air, space, and symmetry to the American home. A gable roof is formed by two sloping sections meeting at the top ridge, forming a triangular shape for the top of window wall of the dormer. The walls of the dormer that extend downward from the gable roof are vertical.
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The Shed Roof Dormer
After the gable roof dormer, probably the second most popular roof shape is the shed dormer. Often taking a pitch similar to the roof of the house, the shed dormer can accommodate small or large windows in a narrow or elongated width. Shed dormers are very common in Craftsman style homes and bungalows.
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The Extended Shed Dormer
Perhaps the most common type of shed dormer is the one extending nearly the full width of a house. In the front or back, this type of shed dormer extends interior space without adding to the footprint of the building. It has been very popular since the 1960s to the present.Continue to 9 of 16 below.
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Arched Eyebrow Dormer
For centuries, the playful British have incorporated small arched windows into their cottage architecture. As these windows enable more light than space to enter interiors, eyebrow windows are often considered more of a window than a dormer. The glazed slits can become very narrow and visually seductive.
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Mansard Roof Dormers
Dormers are common features of Second Empire style homes. François Mansart (1598–1666) modified the gambrel roof by making the sides steeper and inserting windows. The French architect had invented what became known as the Mansard roof, a popular roof style. The windows breaking through the Mansard roof are some of the earliest examples of dormer windows.
Even a more modern building with a Mansard roof likely will have dormers—sometimes both wall dormers (through the cornice) and roof dormers. The elegant and regal Biltmore Estate in Asheville, North Carolina exemplifies the 19th-century Mansard roof dormer on a Chateauesque style large home.Continue to 13 of 16 below.
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Most dormers are roof dormer windows—that is, the structure's roof surrounds the dormer as if it were a skylight. Accounting for snow loads in certain climates, constructing roof dormers is relatively straightforward in both original design and renovations.
A more complicated and some would argue a more elegant design is the dormer that is built through the cornice or the roof's edge. Also called "wall dormers," these "through-the-cornice" dormers are common in grand mansions and upscale neighborhoods.
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An Architect's Eye for Windows
Windows are part of an architect's toolbox. In this Southern California house, the renowned architect Paul Williams (1894–1980) combined different window types in an aesthetically pleasing way. A shed dormer and a wall dormer breaking through the roofline are added to more typical windows and an oriel window to make this English Manor style "cottage" look like a simple country home inside and out.
A good architect will have the education and training to envision design patterns that work for your house.
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Not everyone has the funds to hire an architect the likes of Paul Williams to design your home. Not to worry. Adding a prefabricated dormer to an existing home is an exciting adventure. Consider the challenge, but do your homework. This is not a simple do-it-yourself job as it requires skills in roofing and installing roof flashings, or otherwise you will have leaks. You will need to choose a size of dormer that fits well with your house, draw up a plan, and get the required building permits. You will be removing the roofing in the area of the dormer, so you must be prepared to shield it with a waterproof tarp in case of rain. After opening the roof, you can install a prefab dormer and the flashing needed to keep your installation waterproof.
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The Eyes of Your House
Keep in mind that essentially dormers are windows, and glazing is two-faced. A dormer allows light in and gives you a view out of the room. But it also allows neighbors to look in and changes the appearance of your house from the curb. Dormer windows can make your home come alive. Just look at those eyes.
- "Fleming, John, Honour, Hugh, and Pevsner, Nikolaus. "Dormer Window," The Penguin Dictionary of Architecture. Third Edition, Penguin, 1980, pp. 96-97
- Baker, John Milnes. American House Styles: A Concise Guide. AIA, Norton, 1994, p. 170