Theeaves are the edges of theroof whichoverhang the face of a wall and, normally, project beyond the side of a building. The eaves form an overhang to throw water clear of the walls and may be highly decorated as part of anarchitectural style, such as the Chinesedougong bracket systems.
According to theOxford English Dictionary,eaves is derived from theOld Englishefes (singular), meaning "edge", and consequently forms both the singular and plural of the word.[1][2] This Old English word is itself of Germanic origin, related to the German dialectObsen, and also probably toover.[3]
TheMerriam-Webster dictionary lists the word aseave but notes that it is "usually used in plural".[4]
The primary function of the eaves is to keep rain water off the walls and to prevent the ingress of water at the junction where the roof meets the wall. The eaves may also protect a pathway around the building from the rain, prevent erosion of the footings, and reduce splatter on the wall from rain as it hits the ground.
The secondary function is to control solar penetration as a form ofpassive solar building design; the eaves overhang can be designed to adjust the building'ssolar gain to suit the local climate, the latitude, and orientation of the building.[5]
The eaves overhang may also shelter openings to ventilate the roof space.[6]
Aesthetic, traditional, or purely decorative considerations may prevail over the strictly functional requirements of the eaves. TheArts and Crafts Movement influenced theAmerican Craftsman tradition, which has very wide eaves with decorativebrackets technically calledmodillions, for which there is not necessarily a real functional need; likewise the Italian-style eaves.
The eaves may terminate in afascia, a board running the length of the eaves under the tiles or roof sheets to cap off and protect the exposed rafter ends and to provide grounds on which to fix gutters. At thegables the eaves may extend beyond the gable end wall by projecting thepurlins, or addinglookouts, and are usually capped off bybargeboards to protect the wall and the purlin ends. The overhang at the gable is referred to as agable overhang, as opposed to eave overhang, or they both may be referred to as overhang.
The underside of the eaves may be filled with a horizontalsoffit fixed at right angles to the wall, the soffit may be decorative but it also has the function of sealing the gap between the rafters from vermin and weather.
Eaves must be designed for local wind speeds as the overhang can significantly increase the wind loading on the roof.[7]
The line on the ground under the outer edge of the eaves is theeavesdrip, or dripline, and in typical building planning regulations defines the extent of the building and cannot oversail the property boundary.
Media related toEaves at Wikimedia Commons| Roof shapes |  | |
|---|---|---|
| Roof elements | ||
| International | |
|---|---|
| National | |
