keystone surround

A keystone surround is a polyurethane surround arrangement in which a keystone is added at the centre top of the upper arch part of a window or door surround. On classical and neoclassical openings it is used to emphasise the centre point of an arched surround; the side surrounds, arch profile and keystone together form a continuous frame. The polyurethane pieces are lightweight and applied to the surface with mounting adhesive and screws; they resist moisture and impact, do not crack or blister, and can be painted with exterior facade paint. Being lighter than a plaster surround, installation is fast. Being mould-cast, the surround and keystone details repeat identically on every piece. Polure produces the keystone surround in different span and profile sizes.