How to Install a Cornice – A Step-by-Step Guide for XPS Cornicing

If you are wondering how to install a cornice , You have come to the right place!

Whether you are renovating or doing a new build, installing XPS cornices is one of the easiest ways to upgrade the look of any room. In this guide we’ll walk you through a simple, step by step process to complete your cornicing project with ease even if you are doing it solo!

Thanks to the lightweight nature of XPS (extruded polystyrene) our cornices are incredibly easy to handle , cut and install. With the right adhesive and a few basic tools, anyone can achieve professional looking results and beautiful ceiling cornices

Why choose XPS Cornice?

Xps Ceiling cornices are ideal because they:

Are lightweight and easy to install – even single handed
Stick securely with a simple cornice adhesive or regular cornice cement .
Cut cleanly and accurately for perfect mitres and joins
Are compatible with standard acrylic paint
Xps Cornices comes in a variety of styles and sizes to fit any area.

At Cornice Pro we recommend our own Cornice Adhesive- a smooth non sag formula that makes application a breeze.

Tools You’ll Need

Measuring tape
Chalk line or wall chalk
Cleaning cloth
Cornice adhesive
Mitre box or mitre saw for cutting cornice corners
Sewing pins (optional for holding cornices in place while drying)
Silicone or filler for gaps
120 Grit sandpaper
Water based primer and acrylic paint

Step- by Step : How to install a Ceiling Cornice

Step 1: Measure Your Walls

Measure the full length of each wall where the cornice will be installed .

Add 10-15% extra to account for any offcuts and waste

Clean walls and ceiling edges to remove dust and debris

Lightly sand with 120 – grit sandpaper if surfaces are glossy or uneven then wipe clean again.

Step 2 : Check the cornice fit

Understand your cornice dimensions

Projection- how far it extends along the ceiling

Drop -how far it comes down the wall

Face the visible front surface.

Ensure there is enough clearance from other elements like curtain rails or cabinets

Step 3 : Mark a guideline

Use a chalk line to mark a level guideline along the wall at the drop height of the cornice
Start at the most visible corner of the room usually the wall opposite the entry
Begin with the longest lengths to reduce joins and make installations neater

Step 4 :Cut Cornices at a 45° Angles

Use a mitre box and a fine -toothed saw
Place the cornice upside down in the mitre box
Ceiling edge (projection) faces down, wall edge (drop) against the far side.
Mark the wall side so you don’t confuse orientation.

Cutting tips

Inside corners saw blade points towards corner
Outside corners saw blade points away from the corner
Flip pieces after cutting for correct fit

*If you are having trouble cutting your corners we can cut them for you

Step 5: Apply Adhesive and Fix Cornice

Run adhesive along both long edges and end joins.
Press cornice into place along your guideline.
Use sewing pins or temporary supports if needed to hold while drying.
Wipe away excess adhesive with a damp sponge.

Step 6: Fill and Finish your ceiling cornice

Fill small gaps and mitre joints with cornice adhesive or silicone.
Let the adhesive dry for 24–48 hours.
Once set, lightly sand any filled areas for a smooth finish.
Use a water-based primer before painting.
Only use acrylic paint on XPS cornices

Final Tips for Perfect Cornicing

Always cut and test-fit pieces before applying your cornice adhesive.
Double-check your chalk lines with a level for clean, even installation.
Use matching filler for seamless joins.

Our cornices can fit over existing Cove cornices for an even easier installation.

*Pro tip : If you are installing the cornice over tiles wipe surface with acetone to remove any oily residue and dirt.

If you are installing cornices over brick and timber make sure the surface is as dust free as possible .

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