An eave is the edge of a roof, which is why they are sometimes called roof eaves. On a home's exterior, eaves can project (stick out) beyond the side of the building, serving both decorative and practical functions. The eave of a house has come to mean the underneath area of the roof that projects from the exterior siding, as opposed to a cornice, which is part of the entablature in Classical architecture. Inside your home, usually in the attic, the eave is the angle where the roof meets the outside wall — a good place for insulation, as long as it doesn't get into the soffit (the underside of the overhang).
The architect John Milnes Baker defines eave in this simple way: "the lower edge of a roof which projects beyond the face of the wall."
Think of how a roof extends beyond the siding, and then think about how a hard rain may roll down the roof and onto the ground away from the structure. Centuries ago, the eavesdrop was that indentation line made around a structure when the rain fell off the edge of the roof onto the ground. Anyone standing that close to the house, on the eavesdrop, could overhear what went on within the house itself. That person was called an eavesdropper.
Types of Eaves
A roof can come to an end in basically three ways. A closed eave has very little or no overhang (extension beyond the siding). An open eave has a pronounced overhang, often revealing projecting roof beams or brackets. A box eave is enclosed with a soffit.
What's the Use of Eaves?
An eave can protect the siding and foundation of a structure. A roof eave protruding beyond the sides allows snow and rain to fall from the roof away from the siding, to the ground. The further that the "weather" gets thrown away from the house, the more likely you'll have a dry basement, too.
In hot climates, a large eave on a properly positioned home can provide a sun shade for interior spaces. In rainy climates, the extended eaves of Asian architecture provide shelter from the weather, as well as direction.
In the 21st century, an eave may provide an unobtrusive location for security cameras and light, as can be seen if you look carefully on some of the stately homes on historic Bankers Row in Delray Beach, Floirda.
Also, the eave can help define the architectural style of a building.
About the Word Eave
The word is from the Old English efes, meaning "edge" or "border." It is often misspelled as "eve" or "eeve" as in "house eve" or "eve of house" (definitely not correct!). In Spanish, an eave is an alero. In German, the gutter edge is a traufe. In Portugal, an eave is often called cornija. In Italy, it's a gronda, and in Japan it's a hisashi. Japanese architecture is often designed so that the hisashi becomes the entire exterior, surrounding the center of a building, like the verandas that surround an antebellum French Colonial home.
The Dirty, Little Secret About Eaves
Open eaves invite overnight guests — not the kind of unruly relative that might stopy by for an extended stay, but the kind of pests you may not welcome. The longer the roof overhang, the more protected space that wasps, yellowjackets, hornets, and birds can find to occupy. Without a soffit, birds especially can build their nests tucked in beside your warm house. Even ventilation holes in eaves are entry points for the furry or feathered friend, including bats.
So what do you do? For commercial properties, Avian FlyAway sells "Bird Relocation Systems," which basically are electric grids that keep birds out, much like electric fences keep cattle home on the range. For houses, keeping the eave clean and plugging holes has been the annual maintenance solution. Like everything else home-related, many products involve netting, wire, and sticky stuff. Certain companies like Bird-B-Gone specialize in gels, spikes, and repellents, which sound a lot like hair products.
Fast Facts: Building Styles With Prominent Eaves
When determining the style of a structure, especially houses, look at the eaves as one of the many components that define particular styles. For example, decorative, overhanging eaves on a slightly pitched roof are characteristic of the Italianate style and for some Spanish influenced grand homes. Brackets or corbels find their decorative place in the eaves of this architecture, making homes appear stately
Overhanging eaves are characteristic of Frank Lloyd Wright's Prairie House Style. When the architect had the chance, Wright made the eave more than a byproduct of roof construction. In the 1950s-era Zimmerman House in New Hampshire, Wright used the roof eave as part of the Usonian function.
Beyond the coasts of the United States, the multi-tiered Asian pagoda and the Japanese castle are defined by multiple eaves.
- John Milnes Baker, AIA, American House Styles: A Concise Guide, Norton, 1994, p. 170
- Photo Credits: Japanese Castle, Bernard Annebicque/Sygma via Getty Images; A-Frame House, Paul Lovine via Flickr, Attribution-NonCommercial-NoDerivs 2.0 Generic (CC BY-NC-ND 2.0); Zimmerman and Delray Beach houses, Jackie Craven; Eichler house, Nancy Nehring/Getty Images (cropped); Asian eave detail, Bettmann/Getty Images.