keystone round arch

A keystone round arch is a polyurethane decorative arch element formed by placing a keystone at the centre top of a semicircular round arch. In classical and neoclassical buildings it is used to frame window and door openings with a semicircular arch and emphasise the centre point with a keystone. It integrates with the side surrounds and arch profile. Polyurethane is lightweight and applied to the surface with mounting adhesive and screws; it resists moisture and impact, does not crack or blister, and is paintable. Being much lighter than its stone equivalent, installation is fast. Being mould-cast, the round arch profile and keystone repeat identically on every piece. Polure produces the keystone round arch in different span sizes.