How To Cut Coving Corners: 3 Ways Guide UK (Do This!)

Crown moulding can add a stylish touch to any interior. Its role is to make a smooth transition between the ceiling and walls, hiding an uneven edge and masking painting mistakes.

Installing it is easy, but many beginners struggle with cutting coving corners. If you’ve never installed cornices before, this guide will teach you how to cut the perfect corners.

How To Cut Coving Corners With A Mitre Box

The easiest way to cut coving corners is with a mitre block or box. This tool is designed specifically for the purpose and is very easy to use.

You can use the method below for polystyrene covings. Plaster and PVC cornices could be harder to cut by hand, though.

What You’ll Need

  • Mitre block
  • Crosscut saw
  • Sandpaper
  • Tape measure
  • Pencil

1. Cut Coving Internal Corners

Most coving ranges come with pre-cut corners. However, these ranges are generally more expensive.

If you want to keep home decorating costs to a minimum, you may want to opt for simple cornices and cut the corners yourself.

The secret to cutting coving corners accurately is the right mitre box.

Mitre boxes come in various sizes; buy one large enough to fit your cornices properly. When placed in the box, both edges must lay flat against the bottom and side of the box.

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To cut internal corners, mark two lengths of covings with left and right, based on where they’ll go on the wall.

Place the left coving in the mitre box with the ceiling edge on the bottom. The wall edge must be flush with the side of the block.

Insert the crosscut saw into the 45-degree left-hand corner slot on top of the box (the side farther from you). Run the saw through the 45-degree right-hand corner slot at the bottom of the box (the box side closer to you).

Cut and keep the left-hand length for use.

Do the same for the right piece, but use the opposite slots (right-hand top and left-hand bottom). Keep the right-hand length.

2. Cut Coving External Corners

To cut external corners, mark the lengths of coving with left and right as you did before.

Place the left length in the mitre block and cut at a 45-degree angle using as guides the top slot on the right corner of the box and the bottom slot on the left. Use the piece on the left side.

Mirror the saw position to cut the right corner (top left, bottom right). Use the piece on the right side.

To make things easier for the rest of the corners, you can draw a coving mitre template.

The video below shows you how to use a mitre box:

3. Smooth The Edges

Once you’ve cut all corners, remove all burrs with sandpaper. If you don’t have to use the full length of a cornice, use the tape measure and pencil to mark the portion that you have to cut out. Mitre boxes also have a 90-degree guide you can use to cut cornices to dimension.

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You should also keep in mind that cornices are easier to install on flat ceilings and walls. If yours are finished with Artex, you might want to get rid of the texture first.

How To Cut Coving Corners Without A Mitre Box

The method above works well for polystyrene. If you want to install PVC or plaster moulding, you have to cut the corners with a mitre saw.

Alternatively, you can cut polystyrene covings without a mitre box after marking your own guidelines.

Cutting Crown Moulding Corners With A Mitre Saw

Commonly called a chop saw, a mitre saw is a power tool designed to cut timber at a 45-degree angle.

Change the blade with one designed for polystyrene, plastic, or masonry, based on the material your cornices are made of (polystyrene, PVC, or plaster).

Use the mitre saw as instructed in the user manual to cut internal and external corners.

Cutting Crown Moulding Corners With A Hacksaw

If you don’t have a mitre saw and don’t want to buy a mitre block, use a protractor and ruler to measure 45-degree angles on your polystyrene covings and cut them with a hacksaw.

Follow the same directions you would when cutting with a mitre box to draw the angles and make the cuts.


The easiest way to cut coving corners is with a mitre block. Alternatively, you can use a chop saw or a hacksaw.

No matter what tool you use, remember: to mitre the left side of a corner, cut through left for inside and through right for outside.

To mitre the right side of a corner, cut through right for inside and through left for outside.

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