How to Sand Cornice for a Smooth, Professional Finish

Sanding cornices might not be the most exciting part of a renovation, but it’s an important step if you want a flawless finish. Whether you’re prepping a new cornice for painting or giving an older one a fresh look, doing the job properly will help blend the surface smoothly with your walls and ceiling.

If you’re wondering how to sand cornice or a curved one without damaging the detail, this step-by-step guide will take you through everything you need to know—from the right tools to use, the best sanding techniques, and common mistakes to avoid.

If your project also includes replacing sections of cornice, you might find our how to replace cornice guide helpful.

Different Types of Cornices and How to Sand Them

Not all cornices are the same, and how you sand them depends on the material and design. Here’s a quick guide:

• Plaster Cornices – Strong and durable, but they can develop cracks and rough patches over time. Sanding helps smooth out imperfections before painting.
• Gyprock or Pre-Moulded Cornices – Lightweight and easy to install, but more fragile, so they require a gentler touch when sanding.
• Curved Cornices – These need flexible sanding tools to preserve their shape without flattening the details.

Thinking about upgrading your cornices? Have a look at our decorative plaster cornice collection for ideas.

What You’ll Need: Tools and Preparation

Having the right tools will make sanding easier and give you a smoother, more polished result.

Tools and Materials

• Fine-grit sandpaper (120–240 grit)
• Sanding sponge or flexible sanding block (best for curved cornices)
• Dust mask and safety goggles
• Ladder or scaffolding
• Vacuum or dust sheets for clean-up
• Plaster filler for small cracks or dents
• Soft cloth to wipe away dust

Getting Ready

• Protect the Area – Cover floors and furniture with dust sheets to keep things clean.
• Check for Damage – Look for cracks or uneven spots. Fill any gaps with plaster filler and let it dry completely before sanding.
• Use Good Lighting – Shadows can hide imperfections, so bright lighting will help you spot any areas that need extra attention.

Step-by-Step: How to Sand Cornice the Right Way

Step 1: Start with Light Sanding

Use fine-grit sandpaper or a sanding sponge and lightly smooth out rough spots. Keep the pressure gentle to avoid damaging intricate mouldings.

Step 2: Follow the Shape of the Cornice

For curved or detailed cornices, a flexible sanding sponge is the best option. It bends with the design and helps maintain raised areas. If you’re sanding a curved cornice, avoid using rigid sanding blocks, as they can create sharp edges instead of smooth curves.

Step 3: Blend the Edges

Pay extra attention to the areas where the cornice meets the ceiling and walls. Lightly sanding these edges will create a seamless transition, so the paintwork looks clean and even.

Step 4: Keep the Area Clean as You Work

Dust builds up quickly, which can clog your sandpaper and make sanding less effective. Wipe down the surface regularly with a vacuum or cloth to keep the workspace tidy.

Step 5: Final Smoothing for a Perfect Finish

Once the surface is even, switch to ultra-fine sandpaper (240 grit) and go over the cornice one last time. Run your hand along the surface to check for any missed rough spots before painting.

Common Sanding Mistakes and How to Avoid Them

What Not to Do

• Using coarse sandpaper, which can scratch or damage delicate plasterwork
• Pressing too hard, which can flatten intricate details
• Skipping the cleaning step, which can leave dust trapped under the paint
• Rushing through without checking for a smooth finish

Tips for the Best Results

• Sand in smooth, controlled motions instead of rushing
• Use a sanding sponge for curved areas to maintain the shape
• Wipe down surfaces regularly to prevent dust buildup
• Finish with fine-grit sandpaper for a polished, even finish

Why a Well-Sanded Cornice Makes All the Difference

Sanding might not be the most noticeable part of the job, but it’s what separates a rushed job from a professional-looking finish. Whether you're tidying up an old cornice or working on something more detailed, patience and the right technique will help you keep the details intact while creating a clean surface for painting.

If you're planning to replace or upgrade your cornices, take a look at our decorative plaster cornices, or check out our how to replace cornice guide for expert advice.