Eaves

The eaves are the lower edges of a sloping roof, typically projecting beyond the face of the walls. The word comes from the Old English efes, meaning edge, and is used in the same form for singular and plural, although "eave" is accepted in American dictionaries.

Functions

• Shedding water: the overhang throws rain away from the walls and windows and protects the vulnerable junction between roof and wall.
• Protecting the base of the building: wide eaves reduce splashing and can shelter footings and paths.
• Shading: in passive solar design, eave depth is tuned to latitude and orientation so high summer sun is blocked while lower winter sun reaches windows.
• Ventilation: soffits beneath the eaves often hold intake vents for the roof space.
• Character: deep bracketed eaves define styles such as American Craftsman; East Asian architecture uses elaborate bracket systems (Chinese dougong) to carry deep eaves.

Parts of an eave

• Rafter tails: the projecting ends of rafters or truss top chords.
• Fascia: the vertical board capping the rafter ends, which usually carries the gutter.
• Soffit: the underside lining between fascia and wall; leaving rafters exposed creates an open eave.
• Drip edge or eaves trim: metal at the deck edge.
• Ice barrier / eave protection: a sealed membrane over the deck at the eaves in cold climates.

Design considerations

Deep overhangs increase wind loads on the roof, so they must be designed for local wind speeds. In cold climates the overhang is the coldest part of the roof, which is why ice dams form there and codes require ice barriers measured from the eave edge to a line inside the wall. In planning law the dripline below the eave edge is often used to define the building's footprint relative to property boundaries.

Regional terms

The gutter fixed along the eaves is called an eavestrough in Canada.