How to Replace Cornice for a Clean and Polished Finish

A well-fitted cornice can transform a space, adding a refined touch while covering the junction between walls and ceilings. Whether you're replacing a damaged section or fitting a brand-new length, taking the right approach will help you achieve a smooth, professional result.

This guide takes you through everything you need to know, from selecting the right type of cornice to gathering the right tools and following step-by-step instructions for installation. If you're also working on replacing sections of plasterwork, our how to replace cornice guide has more handy tips to help you get the best match.

When Does a Cornice Need Replacing?

Cornices play both a functional and decorative role. They help conceal gaps, bring character to a room, and create a seamless transition between walls and ceilings. Over time, they can show signs of wear, requiring replacement to maintain the aesthetic and structural integrity of your space.

Common Signs It's Time to Replace a Cornice:

• Cracks or crumbling sections – Age, damp conditions, or impact damage can weaken plaster, leading to gaps or deterioration.
• Style mismatches – Renovations or home extensions often call for new cornices to blend with the existing interior.
• Loose or sagging areas – Poor installation or movement in the structure can cause sections to detach.
• Thick paint layers – Over time, multiple coats of paint can obscure intricate details, making replacement a better option than stripping old paint.

Choosing the Right Cornice for Your Home

Before starting, consider the style of your home and choose a cornice that complements the space. Cornices come in various materials, each with different installation needs.

Types of Cornices:

• Plaster Cornices – A classic option, perfect for period homes and detailed interiors.
• Gyprock or Pre-Moulded Cornices – Lightweight and easier to install, commonly found in contemporary homes.
• Flexible Cornices – Ideal for curved walls or ceilings, providing a smooth, custom finish.

If you're only replacing a section, make sure the new piece matches the existing design and dimensions as closely as possible. Need help measuring? Our how to measure cornice guide can assist. Browse our ceiling plaster cornices collection to find the right style for your home.

Essential Tools and Preparation

Having the right tools makes all the difference in achieving a precise and tidy finish.

What You’ll Need:

• Utility knife and small handsaw
• Hammer and chisel
• Cornice adhesive or plaster
• Measuring tape and pencil
• Mitre box or mitre saw (for accurate corner cuts)
• Sandpaper or sanding sponge
• Protective sheets and safety gear

Getting Ready:

• Protect the Area – Cover floors and furniture to minimise dust and debris.
• Measure and mark cuts – If you're replacing a section, take precise measurements to ensure a snug fit.
• Prepare the surfaces – Make sure the ceiling and walls are dry and free from loose debris so the adhesive bonds properly.

Step-by-Step: How to Replace a Cornice

Step 1: Removing the Old Cornice

• Use a utility knife to score along the edges where the cornice meets the ceiling and wall. This helps prevent damage to surrounding plaster.
• Carefully loosen and remove the cornice using a chisel and hammer. Work slowly to avoid unnecessary damage.

Step 2: Cutting the New Cornice to Size

• If replacing a full length, use a mitre box or mitre saw to make clean, accurate cuts.
• If replacing only a section, measure precisely and cut carefully to ensure a seamless join with the existing cornice.

Step 3: Applying Adhesive and Positioning the Cornice

• Spread a generous layer of adhesive along the back and edges of the new cornice.
• Press it firmly into place, making sure it sits flush against the wall and ceiling.
• Wipe away excess adhesive with a damp cloth before it dries.

Step 4: Securing and Filling Gaps

• Use small nails or temporary supports to hold the cornice in position while the adhesive sets.
• Fill any visible gaps with plaster or additional adhesive to create a smooth transition between the new and existing sections.

Step 5: Sanding and Painting

• Once the adhesive is completely dry, lightly sand the joints to remove rough spots.
• Prime and paint the new cornice to match the rest of the room.

Common Mistakes and How to Avoid Them

Things That Can Go Wrong:

• Incorrect angles on corner cuts – Misaligned joins can be difficult to fix, so take your time with measurements.
• Not using enough adhesive – Weak bonding can lead to loose or sagging cornices over time.
• Rushing the process – Installing before the adhesive has set properly can cause movement and gaps.
• Neglecting to sand and blend seams – Failing to smooth out joints can make the replacement stand out.

Best Practices for a Professional Finish:

• Always double-check measurements before making cuts.
• Use a mitre box for precise corners and clean joins.
• Apply steady pressure when securing the cornice to help it bond properly.
• Blend seams carefully with filler and sanding for a seamless appearance.

Why a Well-Fitted Cornice Makes a Big Difference

Replacing a cornice doesn’t have to be difficult, and with the right tools and approach, you can get professional-looking results without hiring a tradesperson. Whether you're replacing an entire length or just fixing a section, taking your time with each step will give you the best outcome.

For more advice on choosing the right decorative features for your home, browse our ceiling plaster cornices collection or check out our how to measure cornice guide.