Here we shall look at the method of installation for timber coving, though many of the principles mentioned here are applicable to the installation of gypsum based coving. In either scenario, the walls and ceiling must be finished to a suitable standard with either plaster or having been taped and jointed. This provides a clean and consistent surface for the effective installation of the moulding. Unlike where the bottom of the wall meets the floor, the point at which the upper wall meets the ceiling should be finished to a crisp, clean line, aiding in the installation.

The first step is to assess how the coving will sit against the wall. In addition to the different sizes and mouldings of coving available, coving can also be purchased with different “spring angles”. The spring angle of a length of the coving is the amount of tilt present in the length when installed against the wall as intended. This angle is measured in degrees between the wall and through section of the length, with the flats on the back of the moulding being set up to sit flat on both the wall and the ceiling when installed at the correct angle. This can all sound a little complicated, but is easier to see in the illustrations. Off the shelf coving can be purchased with common spring angles of 38, 45, and 52 degrees, though custom spring angles can be purchased from specialist suppliers. A 45 degree spring angle means that the coving will sit at 45 degrees to the wall, and so the distance that the bottom edge projects down from the ceiling is the same as the distance from the top of the wall to the front edge of the coving. A 38 degree spring sits more upright on the wall, with the moulding sitting lower on the wall than it projects onto the ceiling. The opposite is true for a 52 degree spring angle, with the length sitting further over the ceiling with less material projecting down the wall.

Coving is typically sold with the spring angle listed, which is important information to know for cutting the compound angles of the mitres during installation. The manufacturers information might also provide the distance the coving should sit down from the ceiling. If this information is not provided, we must determine this measurement to aid in installation. To do this, cut a small piece from one of the lengths (50mm), and hold it against the upper wall/ceiling intersection. Doing so allows us to see how the moulding is sitting against the wall. The piece can be adjusted so that both of the flats are sitting correctly against the relevant surfaces. Once the piece is situated correctly, the bottom edge can be marked against the wall. This measurement can then be marked intermittently around the room, to ensure that the coving is sat correctly during installation. It’s easy to see how the coving is sitting when we can see the through section. When a whole length is place against the wall, it can be difficult to see if the flats are registering correctly. These registration marks also ensure that longer pieces do not twist along their length.

A slightly longer offcut can be used to mark the top edge of the covings, as it extends past any external corners. This helps to visualize where the apex of the mitre meets, and can aid in marking the pieces for cutting. With all of the appropriate reference marks made, the coving is ready to be cut. The installation of coving imitates the installation procedures of skirting boards to some extent. The longest length are cut first, joined with splayed 45 degree cuts if necessary. Coving can be internally mitred, though a standard internal cope produces a much cleaner and tighter joint. To cut mitres on coving is as follows.

Using a mitre saw makes the process far simpler, though at the very least some form of mitre box is required. Marking the mitres by hand and cutting them freehand is not advised. For mouldings that are not particularly deep, the mitres can be made with a simple 45 mitre degree cut. Place the moulding on the saw or mitre box so that it is upside down. The top edge should lay flat on the saw or box, with the bottom edge sitting against the fence of the saw. A 45 degree mitre cut made in this presentation will produce a 45 degree mitre when the coving is place on the wall in the correct orientation. A 45 degree mitre cut the other way will produce the matching angle to form the full mitre. The coving can be cut slight long on the ground and held in place to mark it against the reference marks. If the corner of the wall is marked on the bottom edge of the coving for an external mitre, this mark will be facing upwards when placed on the saw. This method produces a suitable mitre from a single bevel cut, but will only work for moulding that can be “stood up”. This method also works for any spring angle of coving, as long as the moulding is oriented correctly. Note that cheap mitre boxes can be bought in sizes large enough for wide coving, to avoid having to purchase an expensive mitre saw.

For coving that is wider and will not sit correctly on he saw, the moulding must be laid flat on the saw, with the mitres being cut through the use of a double bevel. Here, the spring angle of the coving must be considered.

To cut the external mitres of coving with a spring angle of 38 of 52 degrees flat on the saw, the mitre angle of the saw must be set to 31.6 degrees, with the bevel angle being set to 33.9 degrees. Many mitre saws feature marking and stops set to these specific angles for the intent of cutting coving. There are 4 different orientations of mitres that we might require when cutting internal and external angles. These are a left and right external mitre, and a left and right internal mitre.

To produce a right hand external mitre - Lay the coving flat on the saw with the bottom edge touching the fence, set the mitre angle 31.6 degrees to the left, and the bevel angle tilted 33.9 degrees to the left, and make a cut on the left hand side of the kept board.

To produce a left hand external mitre - Lay the coving flat on the saw with the top edge touching the fence, set the mitre angle 31.6 degrees to the right, and the bevel angle tilted 33.9 degrees to the left, and make a cut on the left hand side of the kept board.

To produce a right hand internal mitre - Lay the coving flat on the saw with the bottom edge touching the fence, set the mitre angle 31.6 degrees to the left, and the bevel angle tilted 33.9 degrees to the left, and make a cut on the right hand side of the kept board.

To produce a left hand internal mitre - Lay the coving flat on the saw with the top edge touching the fence, set the mitre angle 31.6 degrees to the right, and the bevel angle tilted 33.9 degrees to the left, and make a cut on the right hand side of the kept board.

When cutting coving that has a spring angle of 45 degrees, the procedures remain the same, though the mitre and bevel angles change. The appropriate mitre and bevel angles for 45 degree spring angle coving are 35.3 degrees and 30 degrees respectively.

All of these angles assume that the wall angle, that is - the angle of the wall in relation to a level plane (plumb in almost all instances) - is 90 degrees. In instances where the wall angle is not 90 degrees, the mitre and bevel angles change. Tables can be found online with precalculated results for varied wall angles. That being said, here is the formula for calculating the mitre and bevel angles for any wall and spring angle.

Mitre angle is equal to - arctan⁡(sin⁡(spring angle) / tan⁡(wall angle/2))

Bevel angle is equal to - arcsin⁡(cos ⁡(spring angle) × cos ⁡(wall angle/2))

Of course, in accordance with the practice of cutting successful copes, we must begin with an internal mitre, and so the choice is up to us during installation.

Understanding how the mitres are cut and come together is the most complex part of installation coving, and so from this point, the installation is straightforward. Coving, or crown moulding, is also a common part of craftsman casings, decorative pelmets, as well as many furniture pieces. The procedure for cutting the appropriate mitres remains the same.