Soffit
The finished underside of a roof overhang, eave, staircase, or beam, often ventilated to allow attic airflow.
The soffit is the exposed surface on the underside of an architectural element—most commonly the roof overhang (eave). Soffits are made from wood, vinyl, aluminum, or fiber cement and serve both aesthetic and functional purposes. Vented soffits allow outside air to enter the attic at the eave, flow upward, and exit at ridge vents or gable vents, which is essential for controlling attic moisture and temperature.
Insufficient soffit ventilation is a leading contributor to ice dams in cold climates and premature shingle degradation in hot climates. Building code typically requires 1 square foot of net free ventilation area per 150 square feet of attic floor, split evenly between low (soffit) and high (ridge or gable) vents.
Replacing deteriorated wood soffits with vinyl or fiber cement costs $20–$35 per linear foot installed. Soffit replacement is often done at the same time as fascia and gutter replacement to avoid multiple mobilizations.
Real-World Example
The new vinyl soffits with continuous vent strips replaced the original plywood soffits that had rotted and blocked airflow to the attic.