How to Measure and Cut Crown Moulding

carpentry crown moulding Feb 17, 2021

Installing traditional crown moulding requires patience and effort. Precise measurements and quality cuts ensure a smooth joint between segments. Read on to learn how to cut crown moulding like a professional, as taught by professional carpenter Aaron Butt in his MT Copeland online course Coping Crown Moulding and Trim

Measuring for crown moulding cuts

The most important thing for measuring crown moulding is consistency across a job site. Most builders choose to measure inside corner to inside corner. 

Tools needed

  • Measuring tape
  • Protractor or angle finder
  • Pencil and writing surface

How to measure length

  1. Measure for length first and create a cut list that includes length, type of corner, and type of cut. Also consider drawing a chart of the room with all the corners and adding the measurements to it—this can be very useful.
  2. Take the length measurement from where the crown hits the wall, not the ceiling. This is the bottom run of the crown.
  3. The first measurement and cut should be a flush, square cut along the longest wall. 

Measuring corners

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Mitered corners vs. coped corners

Mitered joints are used to join two corners at 90 degrees using two 45 degree cuts. Mitered joints are quick and easy to make but since walls seldom meet at a perfect right angle, imperfections are simple to spot. Mitered moulding must be cut at the exact right length and angle or a new piece might be needed. Coping those miter cuts allow for a snug fit on a wall or ceiling that is a couple degrees off.  

To measure the angle of the cuts for a corner, use a bevel gauge and protractor or an angle finder tool. When using an angle chart, it is important to know the spring angle of the crown, which is the measured angle between the back of the crown to the wall when the molding is installed.  

Crown typically comes in 45°/45° or 52°/38°. If the spring angle is not known, use a bevel gauge to check the angle or cut test blocks of 45 degree, 52 degree, and 38 degree angles and slide them under the crown.

How to measure corners using a bevel gauge and protractor

  1. Measure with a bevel gauge. Place the stock of a bevel gauge on one side of the corner and rotate the gauge blade until it is flush against the other wall. Transfer that angle to the protractor.
  2. Find the angle. Lay the stock of the gauge flat against the bottom of a protractor and find the angle the blade makes on the protractor.
  3. Calculate the miter angle. Take the angle measurement and subtract it from 180 degrees. Then divide by two. When using the flat method for cutting, this measurement needs to be found on an angle chart to get the correct saw settings.

How to measure corners using an angle finder tool

An angle finder is a small measurement tool used for inside and outside corners. It is simple to move around and can firmly hold any angle from 0 to 90 degrees, making it a great tool for miter joints with irregular walls. Digital models will calculate your miter-bevel cuts for you without an angle chart.

  1. Determine the corner. Angle finders open on a hinge similar to a protractor. Locate the corner that will be measured and open the angle finder. Angle finders have a large rotation that can be used on inside and outside corners.
  2. Capture the angle. Firmly place the edges of the angle finder along the corner walls and lock the angle on the tool.
  3. Take a measurement. With the blades snug against the walls, read the angle and record the measurement.
  4. Calculate the miter angle. Use an angle chart; or, some digital models can calculate the angles on their own. 

How to cut crown moulding

Crown moulding is often cut with a compound miter saw. A miter saw allows trim to be cut at any angle. The fence and base of the saw mimics where walls and ceilings meet at 90 degrees.

 The two main methods for cutting crown moulding are the nested method and the flat method. Both techniques require the use of the powered miter saw. The nested method uses the saw fence and eliminates the need for a bevel cut. The flat method is a compound cut where the bevel and miter angles are cut at the same time. 

Tools needed

  • Miter saw
  • Pencil 
  • Angle chart (flat method only)
  • Eye and ear protection

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Nested method

When using the nesting method, the best practice is to cut the crown upside down. Think of it as if the base of the saw is the ceiling. 

 

  1.  Place the bottom of the crown against the fence of the saw and gently rock until firmly flat against it. 
  2. Once the moulding is set flush against the fence, mark the height of the crown with a pencil. 
  3. Measure the projection of the moulding from the base of the fence to the edge of the crown. The crown will be cut at that angle every time. To maintain the consistency of those spring angles, place the crown stops at the base of the saw. The stops will allow the moulding to lay flat and flush against the fence and base. Some saw models come with stops or you can make stops with extra pieces of wood.
  4. With the saw set and the crown nested securely, make the cuts.

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Inside corner:

For an inside corner on the left side of a wall, set the miter saw at 45 degrees to the right. Save the right end of the cut. To make an inside corner on the right side, move the blade 45 degrees to the left and save the left piece of the cut.

Outside corner:

  • For the left side of an outside corner, pivot the saw to the left and keep the right piece. For the right side of an outside miter joint, move the saw to the right and keep the left end of the cut.

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Flat method

In this method, you’ll take the crown and lay it flat against the base of the saw to make the cuts. This is a compound method that will require bevel and miter angles. When cutting with the flat method, you need to know both the spring angle of the moulding and the bevel. An angle chart will list the appropriate miter-bevel settings for the spring angle of the moulding. 

  1.  Measure the crown moulding spring angle. Use test blocks or use a bevel gauge to find the angle and measure it against a protractor.
  2. Use an angle chart and tilt the saw blade and set it at the appropriate angle for the bevel cut. 
  3. Swing the saw table to set the correct miter angle and make the cut. 

Note: Very few buildings have corners that meet at an exact right angle. Use scrap pieces of moulding to ensure the miter cuts fit well. 

Inside corner:

  • For a left side cut, place the top of the moulding against the fence. Set the bevel and miter angles. Set the miter right and save the left side of the cut. For the right side, set the bottom of the moulding against the fence, miter left, and save the left end of the cut. 

Outside corner:

  • For a left side piece, put the bottom of the moulding against the fence and set the bevel angle. Set the miter base to the left angle and save the right piece. For the right side, set the top of the moulding against the fence, miter right, and save the right end of the cut.

3 Tips for using a miter saw safely

  1. Always make sure the blade is at full speed before cutting. 
  2. Have a firm grip on the piece and make sure that hands are out of the blades path.
  3. Only cut one piece of moulding at a time.

MT Copeland offers video-based online classes that give you a foundation in construction fundamentals with real-world applications, like coping crown moulding. Classes include professionally produced videos taught by practicing craftspeople, and supplementary downloads like quizzes, blueprints, and other materials to help you master the skills.

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