Canadian Woodworking

Installing crown moulding – part one

Author: Roger Knapp
Photos: Roger Knapp
Illustration: James Provost
Published: October November 2009

Of all the trim work in a house, there is probably nothing that makes such an impact as the look of crown moulding around a room.


Crowns add to the quality and value of the home and bring an element of elegance. The placing of crown moulding ties the ceiling and the wall together, not by blending them but by highlighting their different features.

In this three-part series, my intention is to assist all woodworkers out there who may have considered crowns in the past but were unsure about how to cut numerous compound angles correctly. I will walk you through the measuring, cutting and installation process, and give you tips and solutions to overcome prob­lems you may run into. This is definitely a rewarding home improvement project.

In this first part, I will list the tools you will need for the job and go through the process of installing crown around a room with horizontal ceilings. The second part will guide you through installing crown with a sloped or vaulted shape ceiling. I will also discuss combining crowns with other profiles to create the look of custom mill­work. The last segment will be devoted to readers who have a curved wall for crown­ing. The techniques can also be used to make curved hardwood crown moulding for cabinets.

You will need to cut a set of patterns, which will reduce the chance of making a wrong cut, and another set of longer pat­terns to fit crowns in the corners. All my cuts were performed in position with the mitre saw. This meant that the bevel was set at 0 degrees (no compound angles to calculate). Cutting the moulding in the jig greatly reduc­es the chance of cutting the mitre incorrectly and you only have to concern yourself with one angle setting per cut. If you own a com­pound mitre saw and you wish to make the cuts on the flat, a chart for the correct bevel and mitre angles are available from your saw manufacturer’s website.

The material list should include Spackle drywall filler, Dab paintable caulking, a sanding block, wood glue, brad nails, screws for large backing strip and good quality trim paint.
Crown moulding is available in pop­ular hardwoods like oak and maple, and primed softwood and MDF. Oak or maple crowns can be stained and finished to match existing kitchen cabinets.

I chose MDF over finger joint wood moulding because I needed to bend the moulding on a curved wall, and I believe the bending would strain any finger joint to the point of cracking. MDF is a good product to work with. It is light, uniform in shape, is smooth and takes paint well. You will want to choose the size of moulding that looks best for your house. The crown needs to be as wide as or wider than the base­boards or other trims in the room for a balanced look. Also the height of the walls should be considered in your decision.

The first step is to calculate how much material to buy. Walk through the house and roughly measure the rooms, then add 10% to this estimate. Once home you will need to accli­matize the wood for a couple days by placing it in a warm, dry area. You will also want to paint all the mouldings with one coat of quality trim paint. While the moulding is drying there is a lot of prep to do.

Solid surface
 Nailing strips give you a dependable nailing surface onto which the crown can be secured.

Spring angle
This is the angle from the wall to the back of the moulding.

Crown stop
You can buy or make this stop, which will help simplify the compound mitre cuts.

Cutting with the crown stop
 The moulding must be placed upside down on the saw with the bottom flange against the fence and the top  flange against the jig.

Mark the depth
 The use of a depth block will make it easy to mark the crown location. Avoid chalk lines because they can be quite messy.

Cut patterns
 These simple reference pieces will almost eliminate incorrect cuts at the saw.

The preparation

It is important to familiarize yourself with the terminology given to crown moulding.
Which way is up? This is a simple but often overlooked question. Generally, the part of the moulding that has the largest cove profile is the top. Typically the crown will cover more wall than the ceiling.

The spring angle is the angle from the wall to the back of the moulding. The spring angle was measured with the angle finder protractor. Most crown mouldings have a spring angle of 38 or 45 degrees; this is referred as 38/52 or 45/45. You need to know which mould­ing you have before you can cut it and install it correctly. The spring angle needs to be maintained during crown moulding installation to ensure a proper fit at the corners of the room.

You will notice that I have placed the moulding on the inside edge of the framing square and the upper and lower flange are contacting the square. You should read and record the run and the rise of your moulding. The moulding I used was 2″ and 2 ⅝”.
Make a jig (called a crown stop) that can be clamped or attached to your mitre saw so that the moulding can be cut in position. The jig is simply a ¾” plywood, five inches wide and 30 inches long. I fastened the plywood to my Delta saw through two ready-made holes in the base. Plastic crown stops are available at tool stores such as Lee Valley and Busy Bee.

This crown stop jig allows you to cut the moulding ‘in position’ but it has to be placed on the saw upside-down. With this crown stop you will not have to adjust the bevel angle (set at 0 degrees); only the mitre angle will be changed for different cuts. Set the crown stop the dis­tance of the run from the fence, in this case 2″. Having installed the crown stop jig to your saw, and ensuring that the bevel angle is set at 0 degrees, you are ready to make your first cuts. Remember that the moulding must be placed upside down on the saw with the bottom flange against the fence and the top flange against the jig.

You should start off by making the cut patterns. Having these patterns located at the saw to use as a reference will almost prevent cutting the moulding in the wrong angle. Make them about 4″ long and label them ‘right outside,’ ‘left outside,’ ‘right inside’ and ‘left inside.’ While you are at it, cut four longer crown pieces with the same angles as the ‘cut patterns,’ making them 12″ long. They will serve as invaluable tools to fit your moulding to the corners.

Backing strips

Because I used 3 ¼” crown, I was able to use ¾” x ⅞” strips that I ripped from some plywood I had. This strip allowed for a 1/16″ to ⅛” gap between it and the back of the mould­ing. Ensure that the backing strip does not contact the back of the crown as this will prevent the flanges from contacting the wall and ceiling. Attach the strips to the length of the wall with long brad nails ending about six inches from the corners. If you are using wider crown moulding, you will have to rip triangle shaped strips (same angle as the spring angle) from 2×4 or 2×6 material and fasten them to the wall top plate with screws or nails.

The use of backing strips provides for a secure nailing sur­face for the crown moulding. You will not have to search for studs and you can also use shorter nails through the crown. Do not rely on cross-nailing into the drywall and gluing with DAP. Such crown moulding will always be loose and pull away from the ceiling.

Lay-out and measuring

Make a small depth block to mark the bottom flange loca­tion on the walls. Make it 3/4 x 2″ x height of the rise less 1/16″. The reason for making the block shorter than the rise dimen­sion is because you need to take into account the thickness of the drywall filler in the ceiling joint.

Take the depth block and hold it to the corner of the ceil­ing and mark the wall with a sharp pencil. Do this every two to three feet along the wall. Do not mark the corners at this time. If you are mounting a wide crown, place the marks at the studs to which you will be nailing. Do not use a chalk line for this as it is not required and it is messy to clean up. To mark the flange location at the corners, take a pair of the 12″ crown patterns you cut earlier and place them to the cor­ner making sure that the mitre joint is closed tightly. Holding the patterns tightly to the ceiling and ensuring the mitre joint is closed, mark the wall where the lower flange con­tacts. Take note of any poor fit at the corners due to dry-wall filler build-up. Performing this step will ensure that the crown mould­ing will be installed at the correct spring angle and only slight adjust­ment will be required to close the mitre joints. The wall length and the corner angles should be measured at the lower flange pen­cil marks as the dimensions will be different closer to the ceiling because of the build-up of the dry-wall filler.

Now take your angle finder and measure the corner (inside or out­side) angles. Due to the uneven wall surfaces, it is important that you use an angle finder that has legs at least one-foot long. Record this angle accurately and write it on the wall where it will be covered by the crown. The mitre cut will be half of the measured angle. It is normal for the corners to be out of square so make the measurements accurately.

Next, measure and mark the length of all the walls in the room. Write this measurement on the walls for quick reference. If there is a wall that is longer than the 16′ piece, then make your measurements for a scarf-joint over a wall stud.

With the walls measured and the mitre angles recorded and the backing strips nailed in place, you are ready to cut and install. Cut and fit only a couple of mouldings at a time, as you are working with irregular walls and corners. Make the cuts about 1/16″ longer than measured as you may find that the measured length varies from the cut length. Better a little too long and then trim than to have it cut too short.

If the room has an outside cor­ner, I would recommend you start there and work your way around the room. Outside corners can be the most difficult to fit and the most satisfying when the mitre closes up tight.

Following these instructions and tips, combined with a little prac­tice, will give you great results that will improve the look of any room. In the next issue, I will guide you through installing crown with a sloped or vaulted shape ceiling and combining crowns with other profiles to create the look of custom millwork.

Installation tips

• When measuring to an inside corner, instead of bending the tape, measure out 10″ and place a mark on the wall. Now measure the wall to this mark and add 10″ for an accurate reading.
• Support the moulding along its length while cutting, as any sag at the saw will change the angles.
• During installation of the crowns, make use of the 12″ long test pieces at all corners to ensure the best mitre fit possible.
• Apply wood glue to all outside corner joints.
• Use the block plane to remove material from the lower flange to allow the crown to conform to the walls at the corners. There will be times when planing the top edge and the back of the crown, to allow it to fit better along an irregular wall and at a corner, will be required to maintain the spring angle.
• Lay the crown moulding on the wall, aligning the lower flange with most of the pencil marks you put on the wall. Do not expect all marks to be contacted as this is an average only.
• Nail the center of the crown first and work towards the ends. Do not nail closer than two feet from the end until the adjoining moulding is fitted to the corner. This will allow you to twist the crown so the mitre will close along its joint. (If the mitre joint is open at the top or bottom, it is because the spring angle is not maintained and you will have to twist either or both crowns to close the joint).
• Start with the rooms with the longest walls at first so that you will gain experience and confidence. By the time you tackle the washrooms, which generally have much shorter walls and many inside and outside corners, you will be a pro.
• Use a scarf joint when joining crowns. Cut the joint with the crown on its edge against the fence and the mitre set to 30 or 45 degrees. This will result in a shorter joint making it less visible. Also place the overlap half towards the light source or away from the most viewed position. Always glue the joint to ensure it does not separate, and locate it over a stud for added strength.
• Use a drywall filler or smooth Spackle filler for all the nail holes and the outside corners as it will not shrink like Dap. Use Dap paintable caulking for all inside corners and along the length of the upper and lower edges of the crown to create a gap-free finish.
• Perform some final sanding and touch up at the corners and scarf joints and apply a final coat of trim paint.

Tool Up

Most serious woodworkers will already have the required tools. You will need:

  • 10″ mitre saw or compound mitre saw for crowns up to 4 1/4″ wide
  • Brad nailer (2″, 18 gauge) with a portable compressor
  • Adjustable protractor or angle finder
  • Sliding bevel square
  • Large protractor
  • Good quality tape measure
  • Stud finder
  • Block plane
  • Two adjustable stands to support the moulding when being cut
  • Shop-built or store bought jig to support the moulding “in position” on the saw

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