From Wikipedia, the free encyclopedia

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

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

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, it, the ceiling, and the wall form a 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.

Due to the higher cost of woods, crown molding is now available in materials such as plastic and foam.

The calculation of the angles to cut crown moulding is afffected by the angle that the plane of the moulding makes with the walls. Crown moulding is usually sold in either a 45 degree or 38 degree format, so correct angle determination should be made before attempting to cut the moulding.

The formula used to calculate the angle to make the cuts in a spreadsheet is:

• Cell 1 - slope a (in degrees!)
• Cell 2 - A15*PI()/180
• Cell 3 - slope b (in degrees) (note: slopes a and b will be the same when figuring crown molding)
• Cell 4 - C15*PI()/180
• Cell 5 - wall angle (in degrees)
• Cell 6 - E15*PI()/180
• Cell 7 - ATAN((COS(B15)*TAN(D15)+SIN(B15)*COS(F15))/SIN(F15))
• Cell 8 - G15*180/(PI()) = Mitre Angle (in degrees)
• Cell 9 - ATAN((COS(D15)*TAN(B15)+SIN(D15)*COS(G15)/SIN(G15)))
• Cell 10- 90-(I15*180/(PI())) Bevel Angle in degrees

To simplify the cutting process, software can be used to accelerate the calculation process.

• A Web-based mitre angle calculator
• Spreadsheet form using Microsoft Excel
• PerfectCuts, commercial software for determining crown molding angles
• How to install Crown Molding, a full site dedicated to installing crown molding
• How to install crown's angle generator, Bevel & Miter Angle Generator for Cutting on Flat at "How to install Crown"