How to Install Cornice

To install cornice download our easy to follow installation guide, This will explain how to cut the cornice and also how to install cornice.

Step 1: Getting Started

Mark cornice projection on ceiling at each corner of the room then mark a guideline with a chalk line or similar, to ensure the cornice will be straight. Remove all wallpaper, loose paint and dust from where the cornice is to be fitted. Painted surfaces should be suitably roughened to provide a good key.

Step 2: Cutting Cornice Mitres

Cut internal and external mitres with a fine tooth saw using a mitre box. A butt joint will be necessary where the room is longer than the length of cornice. It is best to cut all cornice to the required length in each room and hold in position with temporary partly driven holding nails on the ceiling guidelines and underneath the cornice bottom edge. Each length of cornice may then be taken down in turn (by removing the bottom nails) for the application of cornice cement.

Set cornice ceiling projection on base of the mitre box with guide nails as shown to hold cornice in the correct position while cutting mitres.  This is important for the mitres to fit accurately! Note: The cornice is “upside down” in the mitre box, i.e. the base of the mitre box represents the ceiling. A good rule of thumb for cutting internal mitres is that the wall is always longer. Measure the length of cornice along the wall line.  If this is less than 3 metres, a mitre will be required at each end of the cornice. Some cornice patterns will require matching at the mitres and all patterned cornices matching at joints. With patterned cornice, you may find it easier to mirror the pattern to achieve a flawless mitre. However, some cornice you cannot mirror and have to try continue the pattern. Note: One corner will most likely never match (Blind Corner) We recommend having the blind corner on the corner of the room that is the least seen (usually behind the door.)

Step 3: Mudding up

Mix the cornice cement in a clean container. Using ½ litre of clean water, sift in 850g of cornice cement and leave to soak for about 2 minutes. Stir and mix to a smooth paste which should be stiff enough to spread on the back of the cornice without any tendency to run. It should remain sufficiently plastic to use for about 25 minutes from the time of mixing and set hard in about 1 hour. DO NOT OVERMIX – this will reduce working time. 

Mix water and plaster together to a consistency similar to a pancake mix – A bit thicker than a yoghurts viscosity

Quickly apply the cornice cement approximately 5mm thick and 20mm wide along the back edge of the cornice where contact will be made with the ceiling and wall.

Push the cornice firmly into position and hold on the guideline (Two people may be required). Temporary holding nails can be used underneath the cornice. Excess cement may exude from the edges. This should be removed and used for stopping the mitres and joints or it should be discarded if it has started to stiffen. Finally, the last traces of cement should be removed with a scraper then wiping with a wet brush along the junctions. Remove the temporary holding nails when the cement has set.

Step 4: Final Touches

If needed, mix a small amount of cornice cement in a container and fill any gaps along the wall, ceiling and in the joins and mitres. Try your best to get the mitres and joins smooth and sharp. Once Cement is drying, you can use water and fine sandpaper (180-240 grit) to get a finer finish.