Many people think that cornice is very difficult to install. Others think it very simple because they saw the guy on T.V. do it in half an hour. The truth is cornice can be done by the do it yourselfer, with the right tools and a little bit of patience. Please be aware that this guide is meant for the first time installer, so some of the terminology and things that come as second nature to professionals will be explained thoroughly. There are many schools of thought when it comes to installing cornice; this guide will teach you the method our installers use. It's not to say that the other ways are wrong but we find that this method works very well for us.

One of the advantages of MDF mouldings, unlike plaster, is that the walls and furniture do not have to be covered or draped.  If your house is under construction, the cutting can be done anywhere.  If however you are living in the house, we ALWAYS cut our wood outside, in the garage.  The fine MDF dust would otherwise take days to completely vacuum out.

First we have to look for a large open floor area to cut; normally the garage. Our cornice comes in 12, and 14 foot lengths; look for an area where you will be able to cut lengths of that size. We look for a spot outside otherwise the MDF dust will get everywhere. All cutting is done on the floor using a Compound Miter Saw with a 10 inch draw. The draw is the distance the saw arm can cut in one pull. Although the cornice comes in various widths up to 7 inches, the width of the cornice increases in direct correlation with the angle of the miter.

Start by measuring the walls that are going to be finished. Measure as accurately as possible down to the closest 16th of an inch. Make sure you note the Inside and Outside Corners. To explain inside and outside corners, imagine a perfect square, if you are standing inside the square, you will only see inside corners. If you walk around the outside of the square all you will see is outside corners.

This should allow you to visualize what each corner will look like before cutting. Now that we've cut a few pieces, it's time to pin them up in place. We will require a Compressor and a Pneumatic Finishing Nail Gun.  The reason for the nail gun is simple, when set properly; the nail gun automatically counter sinks the nail heads about a ¼ inch into the cornice. This allows for an easier time when finishing (we'll get to that later). We normally have the compressor set to between 98 and 110 psi. Installers, who have never worked with MDF before, should test and adjust the air pressure as needed for their specific equipment. We find the best fasteners for the job are 15 - 18 gauge brad and pin nails approximately 1 ½ to 2 inches in length. We apply a pair of nails on both the top and the bottom of the cornice every 12- 16 inches in an "X" pattern. The "X" ensures that even if a joist wasn't caught with a nail the cornice will not fall down because the "X" creates a fastener in the drywall.

The placement of the nail on the face of the cornice plays an important part in the installation. If you look at the back of the cornice, you will notice that there are three flat sides to it. The two small angles are the parts that touch the wall and the ceiling. These two angles run along the entire length of the cornice and these are the two areas you should be aiming for when you begin nailing. You should always try to place the nail gun so that the nail head is hidden into a crease on the face of the cornice. Although the nail head is countersunk, the hole is visible sometimes even after we cover it and sand it, whereas in a crease, it disappears.

All corners should be glued using MDF Glue or MitreBond which can be picked up at any of the large box stores. We don't use either white or yellow wood working glue because both of these glues remain slightly flexible, even when they are fully cured. That means that in time they will allow the MDF wood fibres to slip a bit. Manufacturers call this "creep". The solution is to use glues that will cure rock hard. Another thing to consider is that MDF is far more fibrous than solid wood and so using water-based glues will cause "swelling" at the joints. MitreBond is a very thin solvent based glue which results in a virtually invisible seam.

Making an Invisible Solid Joint Like a Pro

Joints are a little different than corners. Joints happen when you have a straight wall that's longer than the available lengths. There is a process that goes along with it in order for the joint not to come apart.

1. If a wall is 16 feet long, we will cut one piece 5 feet and one piece 11 feet. Never cut the wall into two halves, peoples eyes are always drawn to the middle of the wall and so any imperfections will be visible.

2. Do not use a straight cut to join the two pieces. Cut the two ends at 30 degrees to ensure a tight fit and to allow for a larger glue surface.

3. Find a block of wood that is approximately 8 inches in length and narrower than the cornice. Glue this piece to the end that is being joined, ensuring half of it is sticking out at the end in order for the next piece of cornice to be joined to it. Nail this piece of wood in from the front of the cornice. By both nailing and gluing, you ensure that this piece will never move.

4. Next, install the length with the block attached, to the wall.

5. Add a little glue to the face of the block and install the next length just as you normally would. After ensuring a tight fit, add a few nails to ensure the two lengths don't come apart.

Don't Take Chances
All wood, including MDF shrinks a little. To minimize the effect of this shrinkage, which causes unsightly cracks, Elite Mouldings installers use a specially formulated MDF glue, exclusive to  us, on all our joints.

This virtually eliminates service repairs due to shrinkage
In addition, to avoid joints in the seams (which may not show up for up six mouths, we glue a back brace (see photo) behind ALL our seams.  Bracing the back also allows us to make seams disappear.

Do not paint the cornice before you install it, you will have to paint it again anyways after all the sanding is done

Making an Invisible Joint Like a Pro
With a sharp cut and glue, no sanding is necessary!

All machinery used to machine wood will become more efficient when used properly. When it comes to making clean, glass like cuts, a sharp chopsaw blade is in order. As seen in the illustration above, with a sharp cut, there no sanding required. Seams are truly seamless. Three things contribute to a seamless joint:

The use of woodworking machinery and its tooling comes with many inherent risks. Every woodworker should always familiarize themselves with company safety policies. There is no way any course can prevent accidents. Only your skills as an operator and the use of safe practices can prevent accidents. Only work on a safe machine, utilize all guards and personal protective equipment, and do not bypass and interlocks engineered for your protection.

Do not use the same caulking to fill in nail holes, corners or joint seams.

The nail holes, or pin holes, should be sealed and filled with a Spackling Compound. Spackling is a plaster like material that is applied wet and is allowed to dry before being sanded off. It should also be applied generously. A fine (200 grit) sandpaper should be used to sand down the spackling in order to get a smooth finish. The nail holes can easily be filled with a finger and do not need to be sanded. If you use latex dap or caulking for filling in nail holes, you may find that the material will shrink and upon close inspection, will be noticeable.

TIP: We suggest you meticulously dap where the crown meets the ceiling and walls. Secondly would be all inside and outside corners as well as butt joints (where two pieces are joined together).