(from French: soffite, formed as a ceiling; directly from suffictus for suffixus, Latin: suffigere, to fix underneath), in architecture, describes the underside of any construction element.
In popular use, soffit most often refers to the material forming a ceiling from the top of an exterior house wall to the outer edge of the roof, i.e., bridging the gap between a home's siding and the roofline, otherwise known as the eaves. When so constructed, the soffit material is typically screwed or nailed to rafters known as lookout rafters or lookouts for short.
Soffit exposure profile (from wall to fascia) on a building's exterior can vary from a few centimetres (2-3 inches) to 3 feet or more, depending on construction. It can be non-ventilated or ventilated for cooling non livable attic space.
Fascia (/ˈfeɪʃə/) is an architectural term for a frieze or band running horizontally and situated vertically under a roof edge, or which forms the outer surface of a cornice, visible to an observer. Typically consisting of a wooden board or sheet metal.
The word fascia derives from Latin "fascia" meaning "band, bandage, ribbon, swathe". The term is also used, although less commonly, for other such band-like surfaces like a wide, flat trim strip around a doorway, different and separate from the wall surface.
The horizontal "fascia board" which caps the end of rafters outside a building may be used to hold the rain gutter. The finished surface below the fascia and rafters is called the soffit or eave.
In classical architecture, the fascia is the plain, wide band across the bottom of the entablature, directly above the columns. The "guttae" or drip edge was mounted on the fascia in the Doric order, below the triglyph.