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A newly installed and patched white cornice around the corner between the ceiling and wall.

Overview

Adding a cornice to your walls is a simple way to enhance the look of your home. Whether you're tackling a fresh installation or replacing old cornices, this guide will show you how to cut and install cornice like a pro.

Safety tip: Always wear the appropriate safety equipment (safety glasses, gloves, ear muffs and a mask, for example) and always follow the instructions for the product or equipment.

Steps

1Choose the right cornice

Before starting, choose the cornice profile that best suits your room. Cornices come in different styles, from simple cove designs to more decorative cornice options. In this guide, we’re working with a 55mm cove cornice, which is simple and versatile for most homes.
A partially plastered wall with a ceiling cornice seems ready for painting or finishing work.

2Remove existing cornice

If you’re replacing old cornice, you’ll need to remove the old cornice and plaster. Start by carefully scoring along the edges where the cornice meets the wall and ceiling using a utility knife. This helps prevent damage to the surrounding surfaces.

Next, use a wide scraper to loosen the cornice. Insert the scraper gently at the edge and work your way along, applying even pressure to pry the cornice away from the wall and ceiling. For stubborn areas, you can tap the handle of the scraper lightly with a mallet to ease the cornice off. Once the cornice is removed, clean the exposed area by scraping off any remaining adhesive and cornice plaster as this ensures the new cornice will sit flush.

A person is using a utility knife to remove the old cornice by carefully scraping along the edges where it meets the wall and ceiling.

3Mark the cut direction

Now you’re ready to install the new cornice. To help with alignment, mark where the new cornice will go on the wall and ceiling: For a 55mm cove cornice, make a mark 55mm down from the ceiling on the wall and 55mm out from the wall on the ceiling. Use a chalk line or pencil to create a continuous guide along the length of the wall and ceiling for precise placement.

Next, measure the length of your cornice carefully, remembering:

  • For internal mitres (inside corners where two walls meet), measure to the long point of the angle.
  • For external mitres (where the cornice wraps around an external corner), measure to the short point.

Mark the cutting direction clearly on your cornice to avoid mistakes. Always double-check your measurements and marks before cutting.

A person is using a measuring tape and pencil to measure and mark a wall for accurate alignment.

4Place the cornice in the mitre box

Use a pencil to mark the direction of the cut on your cornice. This helps keep track of your orientation and avoids confusion when you’re ready to cut. Always double-check your marks to make sure they’re accurate. Place the cornice carefully in a mitre box. Most mitre boxes have steps for different cornice sizes (e.g., 55mm, 75mm, 90mm), so position yours accordingly.

 

Tip: If you’re cutting the right side of the cornice, flip it so it’s on your left side in the mitre box. This might sound confusing, but flipping the cornice ensures your cut is accurate.
A person wearing a red shirt is holding a wooden mitre box to position the cornice.

5Cut the cornice

Using a hand saw, cut along the marked angle in the mitre box. Hold the cornice firmly in place to prevent any movement while cutting. Once the cut is complete, check the fit by holding the cornice up to the wall or ceiling. Make any minor adjustments if needed.

A person is using a hand saw and a wooden mitre box to cut a cornice.

6Mix the cornice cement

Prepare the cornice cement according to the manufacturer’s instructions. The ideal consistency is thick but still spreadable, similar to butter. This ensures a strong bond between the cornice, wall, and ceiling.

A person is using a drill with a mixing attachment to prepare cornice cement in a bucket.

7Apply the cornice cement

Use a scraper to apply a generous amount of cornice cement along the edges of the cornice where it will contact the wall and ceiling. Spread it evenly for a secure fit. Press the cornice into place, making sure it aligns with the marks on the wall and ceiling. To keep the cornice steady while the cement sets, insert screws along the length of the cornice. Be gentle to avoid damaging the surface of the cornice.

A person wearing safety glasses and a red shirt is applying a cornice onto the ceiling with their hands.

8 Clean and smooth the joints

Once the cornice is installed, scrape off any excess cornice cement with a trowel or broad knife. Fill in any gaps or screw holes with cornice cement. After a few minutes, use a damp sponge to smooth the surface and remove any remaining excess. This will leave you with a clean, seamless finish.

A person is using a broad knife to remove excess cement around a freshly installed cornice on the wall.

9Fill any screw holes and gaps

Once the cement has fully dried, fill any screw holes or gaps with filler. Use a filling knife to smooth the filler so it’s flush with the surface.

A person is applying filler to screw holes on a cornice using a scraper.

10Sand the area

After the filler has dried, sand the area lightly with sandpaper to remove any rough patches. Wipe the area with a microfibre cloth to remove dust and your cornice will now be fully installed.

11Now that you’ve installed cornice…

Health & Safety

Please make sure you use all equipment appropriately and safely when following the advice in these D.I.Y. videos. You need to be familiar with how to use equipment safely and follow the instructions that came with the equipment. If you are unsure, you may feel it is safest to consult an expert, such as the manufacturer or an expert Bunnings Team Member.

Grave health hazards are linked to asbestos, which may be in homes built up to 1990. Health hazards may result from exposure to lead-based paints in older materials and copper chromium arsenic (CCA) treated timber. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer.