A fiberglass siding piece may be formed. The fiberglass siding piece includes an upper seating portion of the fiberglass siding piece. The upper seating portion includes an angled siding seat. The fiberglass siding piece further includes a main portion of the fiberglass siding piece, and a lower seating portion of the fiberglass siding piece. The lower seating portion includes an angled siding seat. The angled siding seat of the upper seating portion is configured to receive the angled siding seat of the lower seating portion of an adjacent fiberglass siding piece. The upper seating portion may include slots configured to accept fasteners to fasten the fiberglass siding piece to a building.