Crown molding

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.

[edit] Installation

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.

[edit] Angle calculations

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.