The answer to 'what is fascia' is the horizontal board that runs along the lower edge of a roof, covering the ends of the roof rafters. Fascia boards provide a clean, finished look to the roofline and also serve an important functional purpose by protecting the rafter ends from the elements. Fascia is typically made of wood, vinyl, or aluminum and comes in a variety of colors to complement the home's exterior.
Fascia boards play a critical role in roof drainage and water management. They help direct rainwater and snowmelt away from the home's foundation and siding. Properly installed and maintained fascia can prevent rotting, mold, and other moisture-related damage to the home's structure.