Crown molding

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Crown moulding encapsulates a large family of mouldings 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 mouldings have generally made their appearance as mostly decorated plaster or wooden trim where walls meet ceilings.

[edit] Installation

Crown moulding 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 moulding'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 mitre 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 mitres.

Another way and the easiest way to install crown moulding is by using crown corner blocks. This eliminates the need for mitre cuts or coping; the moulding is installed with a straight flat cut.

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

[edit] Angle calculations

The calculation of the angles to cut crown moulding is affected 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()) = Miter 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.

[edit] External links

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