What Is an Eave and What Does It Do?

All About Eaves

A new home with four roof lines and four separate eaves
A House Can Be Designed With Many Eaves. Photo by Fuse / Corbis / Getty Images

An eave is the edge of a roof. On the outside of your home, 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.

Centuries ago, the eavesdrop was the 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.

Definition of Eave:

"the lower edge of a roof which projects beyond the face of the wall."—John Milnes Baker, AIA

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.
  • A box eave is enclosed with a soffit.

What does an eave do?

  1. An eave can protect the siding 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.
  2. In hot climates, a large eave on a properly positioned home can provide a sun shade for interior spaces.
  1. The eave can help define the architectural style of a building.

An Element That Defines an Architectural Style:

When determining the style of a house, look at the eaves as one of the many components that define style.

  • Overhanging eaves are characteristic of the Prairie House Style.
  • A-Frame houses have eaves that can reach ground level.
  • Decorative, overhanging eaves on a slightly pitched roof are characteristic of Italianate style.
  • Eichler Houses exaggerated the eave to define a mid-20th century architectural style.
  • The Asian pagoda is defined by tiers of multiple eaves.

Origin of the word Eave:

The word is from the Old English efes, meaning "edge" or "border." It is often misspelled as "eve" or "eeve." 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.

Who Is That Nesting In My Eave?

Open eaves invite overnight guests—the kind of pests you may not welcome (like your brother-in-law?). The longer the roof overhang, the more protected space that insects 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 Avian Averting 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 involving netting, wire, and sticky stuff are available to the homeowner. Certain companies like Bird-B-Gone specialize in their offerings of gel, spikes, and repellent.
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More About Eaves:

Source: American House Styles: A Concise Guide by John Milnes Baker, AIA, Norton, 1994, p. 170