17th May 2022 What is a Shadowline ceiling? A Shadowline ceiling is a treatment where a traditional cornice mould is not used. Instead, a shadowline using a metal angle is created in the ceiling where it connects to the wall. This differs to square-set where a 90 degree angle between the walls is used without a shadowline. It is common when selecting a Shadowline ceiling to complement the contemporary modern style with Shadowline skirting and doorjambs to provide a consistent style. The Intrim Shadowline system is not available for ceilings.