Eaves are the horizontal section of a roof that extends beyond the outside wall of a structure. The sloped connection between a gable or shed roof and an exterior wall is called a rake. Building eaves provide protection to buildings. The overhang created by eaves prevents rain, snow and other debris from spilling directly down the side of the building and causing damage to the siding or foundation.
In addition to their mundane function, roof eaves have historically been used as architectural features. In Dutch Colonial houses, the bottom tips of flared roof eaves curve up and away from the roof creating a silhouette reminiscent of traditional Dutch caps. Frank Lloyd Wright used sweeping, elongated eaves on his prairie style residential homes to create flowing lines seemingly connected with the earth. Traditional Asian architecture of the Zhou period took advantage of extended sloping building eaves to construct the intricate painted designs, as is common on pagodas.
There are four basic types of eaves: exposed, soffited, boxed-in and abbreviated. In an exposed eave, the finished underside of the roof and its supporting rafters are viewable from underneath. The soffited eave adds a finish, or soffit, board that connects the bottom tip of the eave with the side of the building at a 90 degree angle. This creates a smooth surface when viewed from beneath. A boxed-in eave also encases the roof rafters when viewed from below, but meets the side of the building at the same angle as the roof itself. An abbreviated eave is cut off almost perpendicular with the side of the house.
Eave detail for the exposed, soffited and boxed-in types of eaves includes air vents to prevent over-heating during warm weather and condensation leading to rot during cool/wet weather. Eave flashing is installed under roofing material and wrapped over the edge of the eave to prevent wind and water damage. This is especially important where the edges of the eave meet the gable, or rake.
Over time, the word eave has also come to mean the enclosed space between the intersection of the roof with internal and external walls of a building. This occurs in buildings where a portion, or the entirety, of the ceiling is parallel rather than perpendicular to the roof – creating a sloping ceiling – which is terminated at some point by a partial wall called a knee wall. The space between the knee wall and the outside wall is commonly called the eaves and is most often used for storage. This kind of eave is common in traditional New England cape and farmhouse style houses.