Installing Crown Molding: The Ultimate Guide

Simple and inexpensive design accents, such as crown molding, can add class and sophistication to any home interior. Traditionally, crown molding was carved from heavy hardwood and was considered very difficult and cumbersome to install. Things have changed, and today crown molding is made from polyurethane foam and is more affordable, lightweight, and looks just as beautiful as its predecessors.
Most crown molding is pre-primed and ready to accept latex or oil based paint application. The following guide will assist you in properly installing crown molding that has been purchased online and delivered to your home for optimal interior design.
Items you will need before you begin:

• Miter box


• Hand saw or power miter saw


• Caulking gun


• Premium paintable, silicon or super latex adhesive caulk


• Caulk line box and pencil


• Tape measure

Optional (but recommended) materials:

• 1.5" – 2.0" putty knife


• Hammer and nail set


• Elastomeric adhesive caulk (White Lightning™ Recommended)


• Extra fine sandpaper


• 6d or 8d finishing nails (bright finished or electro galvanized) fasteners must penetrate substrate a minimum of ½ to ¾ inch

Preparing your room for crown molding installation

• Before you begin installing your crown molding, it's good to plan your layout in order to determine the amount of crown molding you'll need.


• Measure the entire room (the width of every wall) to find the total length.


• Add 10% to this total for miter waste


• Divide the total linear feet buy the crown molding lengths. These lengths usually come in eight, 12, and 16 foot measures. So if your total wall length is 34 feet and you're using eight foot molding lengths, this means you'll need five lengths of eight foot molding at a 40 feet total. You'll always want to round-up. It's better to have more molding than not enough.


• If you're not using cornices, consider buying additional molding in order to match the pattern of the molding when you're eight foot length ends in the middle of a wall. If your molding has a repeat pattern of 6" or greater, you'll want to purchase an extra 5% of molding.


• Always store your molding in a dry area and never outside.

Things to consider before installing your crown molding

• It is recommended that you paint after installation since the caulk that you'll by using to help secure the molding to the wall will push through the joints and may create some white areas within the crown molding gaps. You'll also be using the caulk to cover the nail/screw holes created when mounting the molding to the substrate. You'll be using a putty knife to fill these holes and later, extra fine sandpaper to smooth-out the caulk for painting or staining.


• Clean all surfaces of molding with a cloth or wet sponge. Make sure surface area is completely dry before installing.

Measuring and mitering your molding for installation

• The first piece of crown molding to be cut should be a piece that will be behind a door or at an inconspicuous corner. This is because when matching molding patterns, where the total installed length of molding begins and ends, the pattern will usually not match-up.


• Measure the length of the wall the crown molding is to be installed on. When cutting your crown molding length, add 1/32" to either side to compensate for taking.


• Place the molding in the miter box and make sure to be aware of the wall facing side of the molding and the ceiling facing side. The wall facing side is usually the longer side of the molding. It would be good practice to always place the ceiling side of the molding on the bottom of the miter box and the wall side of the molding on the miter box wall opposite you.


• Measure the joint angles of your walls (inside and outside angles) with a good protractor. For cutting joints, measure the angle where two walls meet and divide this angel in half. This divided amount will be the angle you'll want to cut the molding joint at.


• When cutting, take note of the molding pattern. Cut the left side piece of molding first and then match the pattern before cutting the right side piece. Do this for all joints, inside and out.


• After cutting, place your cuts together to check how they fit. If it looks good, move on to the next molding length to be measured and cut.


• As you're cutting and mitering all your molding lengths, lay them down in front of the walls that they're to be installed on. Do this until you've finished cutting all molding lengths and double check them for correct measurement.

Crown molding butt joints

• Sometimes when crown molding does not span the entire length of a wall, you'll need to butt joint two crown molding lengths together.


• Make sure there is pattern continuity between the two lengths of crown molding to be joined.


• Place the crown molding in the miter box and cut a straight edge.

Installing your cut crown molding

• The first piece of crown molding you'll want to install is the piece you cut first.


• Take the molding and add a continuous bead of ¼" construction adhesive caulk along the ceiling and wall facing sides of the crown molding, as well as the butt joint ends. Gently press the crown molding against the wall and use the caulk to fill in any gaps.


• Next, nail or fasten the molding into place using trimhead drywall screws or finishing nails. Make sure to place the nails into areas of the molding where there is no ornamentation so that the nail or screw hole can be filled with elastomeric caulk and later sanded down to a smooth finish.


• After the molding is secured there may be some adhesive caulk that has been pushed out around the edges and joints of the molding. Wipe off the excess caulk using a wet cloth. Caulk will usually dry in two to three hours.


• Once the molding has been installed fill all gaps with caulk. Smooth with a putty knife, wipe off excess and allow to dry.


• Sand down caulked areas to a smooth finish to prepare for painting or staining.


• Paint or touch-up molding with paint or stain as needed.

This comprehensive crown molding installation guide has been brought to you by InvitingHome.com. Remember - when installing a cornice or crown molding it is important to establish a plan for the layout prior to commencement. Measure twice, cut once and use these handy instructions to give your home the classy interior décor you've always dreamed of.

Neel johnson holds a B.A. in Religion from Columbia University and an M.A. in New Media from Emerson College. In his spare time, he enjoys doing things on purpose.