Cutting and Applying Plaster-based Cornice to Beautify Your Living Room
Ceiling Feature with Light-weight Cornice Added
Tools and Materials for Application of Cornice
Methods are shown for attempting fixing of plaster-based cornice features to adorn ceilings.
When carrying out such tasks, it would be advisable to have the help of another person, as each length of cornice is quite long. Four hands will make the job easier than two hands can manage.
There are no specialist tools required for making interior and exterior cuts.
An instructional video is placed near the bottom of this article showing the entire process from start to completion.
- Enough cornice to complete the entire perimeter of the room.
- A type of PVA sealer / primer, that will diminish porosity prior to fixing cornice.
- A bag of texture compound.
- An ordinary woodcutting jack-saw.
- A pencil for marking out.
- Fine grade sandpaper.
- A wide scraper and a caulking tool (such as a flat trowel kind of tool, whereas a caulker is made from wood and plastic and is used to apply material such as filler or texture, and used for smoothing and for feathering the material into the surface.)
- A bucket to mix the fixing/filling compound and a mixing device to mix from powder form.
- A means for you to reach the ceiling / wall area.
- Paintbrush and soft sponges for cleaning and blending.
3 Stages for Marking Cornice
1: Using an ordinary jack-saw, cut a small length of cornice, about six inches long, get onto a ladder or hop up and hold the piece directly up to the ceiling / wall edge, at the correct angle and directly against the wall. (Set it against the very corner.)
The correct angle to offer the cornice would be 50% against the wall and 50% against the ceiling.
2: With a pencil, run it along the top of the cornice to create a mark onto the ceiling directly from the corner of the room, and about 6 inches long. Also mark a six inch line onto the wall directly underneath the cornice.
3: Take the same piece and offer to the adjoining wall directly next to the wall you just marked, and make a pencil line onto both the wall and the ceiling.
You should have made 4 pencil marks where the two marks make a cross onto the ceiling. On each wall you will also have drawn a line.
The two pencil lines on each wall can be around 4-5 inches long of which will act as a guide ensuring each length of cornice will match the same level all around the room, once completed.
A Single Step Featuring Plaster Cornice
Steps for Marking Interior Angles prior to Cutting
4: Hold an entire length of cornice up to the wall / ceiling and against the corner. Line this piece up with the ceiling and wall marks you have made. The pencil cross mark on the ceiling is where to mark onto the cornice.
5: Take another new length and do the same on the adjoining wall, marking the cornice.
The marks are ready for cutting interior miters at the correct angle.
Steps for Cutting Interior Angle Miters
6: Cutting the length of cornice: lay the piece on its back onto a flat surface, with the finished edge facing you. Hold the saw onto the very end of the cornice and slide the saw so that it moves to meet the pencil mark drawn onto the cornice. This would equate to a 45% angle. Tilt the saw over so that it resembles another 45% angle.
When you have sliced off the end, there would be a 45% angle of cornice removed. Do the same with the next piece of cornice. These two pieces of cornice will slot perfectly against each other.
Adhesion Principals: Ensuring Cornice Does Not Fall Down
Because the texture compound is mixed with water, the vital step prior to fixing is to make sure the ceiling and wall area is not porous. If adhesive compound is applied onto a porous surface, the adhesive would dry off too quickly and will forfeit its ability to adhere adequately.
7: Mix a propriety PVA SEALER (primer) with water as per the instructions for porous surfaces. Paint this solution onto the top of the wall and the edge of the ceiling, where the pieces are to be fitted, and leave to dry completely prior to fixing.
This Design shows Cornice over a Step Down Ceiling Feature
Exterior and Interior Miter Cuts. Angles. Butting Joins
For one piece of cornice to meet directly against another piece, it is not a good idea to butt one end directly to the another end as this will look untidy. In this case the finished joint may show, so a slight angle cut from the 2 pieces will be required.
How to overcome this problem:
Set your saw at an angle onto the end of the piece that you want to butt. Slightly tilt the saw prior to cutting the end off. Prior to applying another piece next to this one you may also cut the new piece in the same manner
Marking and Cutting Exterior Miters
Exterior, or outer miter cuts, are required when cornice is applied around protruding obstacles such as breast walls or similar obstacles.
As with interior miters, use a piece as a guide to make correct measurements prior to cutting and fixing.
8: Offer the piece to the ceiling / wall making sure it is at the correct angle.
It should overrun the edge of the obstacle by around 5-6 inches. Take a pencil and mark along the ceiling, following the top of the cornice.
9: Hold the piece against the adjoining part of the obstacle. Again, draw a pencil mark onto the ceiling.
Two pencil marks will make a cross on the ceiling at the corner of the protruding obstacle.
10: Use an entire length around 5-6 inches longer than the actual area intended to cornice. Hold against the corner of the wall / ceiling at the correct angle and pencil-mark on the piece where the cross is. Take a fresh piece for the other wall / ceiling edge and mark this in the same manner, using the same angles and titling methods to cut away the exterior miters.
Fixing: Adhesive Compound
Texture compound with PVA SEALER added makes ideal adhesive for light-weight plaster-based cornice.
11: Apply a generous amount of PVA to clean water prior to adding texture powder, making sure the PVA is mixed thoroughly with the water prior to adding texture.
12: Lay the piece of cornice onto its front. Using a scraper, lay a generous amount of compound onto the back of the cornice. Fix the first piece to the ceiling / wall.
Essential Tips for Success when Fixing Cornice
These steps are important for the job to run smooth and the finish to be professional.
Get the first piece of cornice fixed up there.
Even though you may have already cut the second piece ready for fixing, sometimes the next piece may not match perfectly. In other words the angle cut may be slightly out.
Once the first piece is adhered onto the ceiling this is the opportunity to hold the next piece in place. You may see more needs to be cut away of the new piece so that it will fit neatly into the first.
Do this test prior to fitting any next pieces up. Place up to the area before applying compound and you will see if any slight cuts may be required for that piece you to fit neatly against the next piece.
The adhesive needs to be mixed up sufficiently thick so that it wall take the weight of the cornice.
Another aspect of the thick mixed texture material is used for filling joints, butts and the corners, where necessary.
Clean up each piece as you go along. Do not allow the adhesive to dry otherwise you may need to sand off later.
Take into consideration that texture mixed with water will shrink slightly once dried. Therefore a second filling in the corners and butt joins afterwards, may be required.