cornice

In this how-to video from Porta, Ed explains how to install a cornice to cover the gap between the wall and the ceiling.
A decorative way to tidy up the junction between the wall and the ceiling is using a crown moulding.
The intricate shape of moulding causes some challenges when joining in a corner.
A basic mitre joint can cause issues if the walls are slightly out of square, as the joint will leave a gap at the front. The best option is to use a scribe joint, in which the shape of the moulding is reproduced at the end of the moulding.
Although they are intricate to cut, when the two pieces come together they allow for walls being out of square.
The first step is cutting the moulding at a 45 degree angle. The moulding must be cut oriented the same way that it will be installed, so make a simple jig by joining two pieces of timber at a right angle along the edges and adding a lip.
Once the moulding has been cut, use the same jig to hold the moulding in place and cut along the profile of the moulding at a slight angle to create a back cut, allowing for any walls that are slightly out of square.
On the longest wall, the moulding should be cut flush with either wall.
To install the cornice, secure the longest piece first using nails, then secure the other pieces, ensuring that the scribe joints are flush.