The answer to 'what causes fascia' is that fascia boards are the horizontal boards that run along the lower edge of a roof, connecting the roofing material to the exterior walls of a home. Fascia boards serve several important purposes, including:
Protecting the roof edge - Fascia boards provide a finished, weatherproof edge to the roof that helps prevent water damage and rotting of the roof structure. They also support the lower edge of the roof shingles or other roofing material.
Providing a mounting point - Fascia boards give a solid attachment point for gutters, downspouts, and other roofing accessories that need to be securely mounted to the home's exterior.