Polyurethane(PU) Crown Molding

Polyurethane(PU) Crown molding encapsulates a large family of moldings which are designed to gracefully flare out to a finished top edge. PU Crown molding is generally used for capping walls, pilasters, and cabinets, and is used extensively in the creation of interior and exterior cornice assemblies and door and window hoods.

In recent times, PU crown moldings have generally made their appearance as mostly decorated plaster or wooden trim where walls meet ceilings.

Installation
PU Crown molding is typically applied along the seams where ceiling meets wall. Usually it is not placed flush against the wall nor against the ceiling. Instead, when viewed from the molding's end (or as a cross-section), it, the ceiling, and the wall form a "hollow" triangle. This adds a difficulty to the installation process, namely the need for complex cuts to form corners where two walls meet.

There are two common ways to fashion inside corners. One is to use a compound miter saw to cut the ends of the corner pieces along two axes simultaneously. The other, called coping, is a two step process, first to cut a simple miter and then to use a coping saw to undercut the miters.

Many different companies now manufacture crown molding in materials such as plastic and foam. These typically are offered with corner blocks, and are popular with DIY home improvement enthusiasts.

The use of a coped joint for interior corners saves the trouble of having to determine and cut the exact inside degree measurement, since most corners are not exactly 90/45 degrees. Outside corners must be mitered, and care must be taken in measuring and cutting, since not all outside corners measure true. If the angle is not exactly 45/22.5 degrees, a corner measuring device or piece of scrap crown molding may be used to obtain the right measurement before the final cut is made.