keystone surround arch

A keystone surround arch is a polyurethane arch piece formed by placing a keystone at the centre top of the upper curved part of an arched surround. On window and door openings it joins with the side surrounds to form a curved upper frame, with the keystone emphasising the centre point. It is used on classical-style facades and in interiors. Polyurethane is lightweight and attaches directly to the surface with mounting adhesive; it resists moisture and impact, does not crack or blister, and is paintable. Being much lighter than a stone arch, it is easy to install even on high openings. Being mould-cast, the arch and keystone details are identical on every piece. Polure produces the keystone surround arch in different span and profile sizes.