How to Kerf Mouldings for Curved Walls

Installing curved moulding profiles to an interior space doesn’t have to be difficult – when you know how to kerf. Whether you’re a professional builder, carpenter, installer, or a capable DIYer, understanding the kerfing process is essential for achieving seamless curved trims.

 In this guide, we break down how to prepare and install curved mouldings using kerf cuts, and we’ll show you how this works in real life with a video from our expert installation partner, Opulent Finishes.

Watch the process, learn the technique, and see how Intrim’s inlay mouldings can be shaped into flawless wainscoting on a curved wall.

Watch: How Opulent Finishes Kerf and Install Curved Mouldings

In this short video, our preferred installer partner Opulent Finishes shows how they kerf Intrim’s inlay moulds to suit a curved wall — from cutting the kerfs to bending, installing, and finishing the trim. This video provides a clear look at the kerfing technique in action, making it easier to visualise how you might apply this method on your own project.

The video above shows kerfing being applied to a concave/internal wall, however, this method works for both concave (curving inward) and convex (curving outward) walls.

What is Kerfing?

Kerfing is a technique that involves making a series of shallow cuts (called kerfs) along the back of a timber moulding to make it flexible enough to bend around a curve. This method allows rigid mouldings – like inlay moulds or chair rails – to be used on arched walls, columns, or curved staircases without cracking.

Step-by-Step: How to Kerf and Install Curved Mouldings

1. Understand the Curve and Select the Right Profile

• Measure your wall radius or curvature accurately.

• Choose a moulding with a flat back and consistent thickness – Intrim’s inlay moulds are ideal for this.

• Avoid dense hardwoods, instead opt for a primed MDF.

2. Make Kerf Cuts

• Use a drop saw with a fine blade.

• Cut shallow grooves (kerfs) along the back side of the moulding.

• Space the cuts closely together (typically every 5 – 8mm) depending on the tightness of the curve. Use an online kerf spacing calculator to determine the ideal spacing for your project.

• Leave enough material between the kerfs to maintain strength while allowing flexibility.

• Maintain consistent kerf spacing and depth to avoid breaking the profile during bending.

3. Test Fit the Curve

• Gently bend the kerfed moulding into position.

• Use temporary fasteners (like clamps or nails) to hold in place.

• Check the fit and adjust kerfs if necessary.

Tip: Use thin MDF or cardboard templates to pre-check your curve profile.

4. Apply Adhesive and Fix in Place

• Apply flexible construction adhesive such as Intrim’s Intensive Grip Adhesive to the back of the moulding.

• Fix the moulding into place using brads or nails, ensuring consistent pressure along the curve while the glue sets.

• For higher walls or ceilings, mechanical fasteners are recommended.

5. Fill, Sand, and Finish

• User filler to close any visible kerf lines or nail holes. Opulent Finishes recommends Selleys Linseed Oil Special Putty and Selleys Plastibond Heavy Duty Bog.

• Sand smooth and apply primer or paint as required.

• The final result: seamless, architectural wainscoting or trim on a curved wall.

Why Kerfing Works for Trade Professionals

Curved moulding installation often seems complex, but with kerfing, you can can:

• Deliver high-end, custom finishes without custom curved moulding manufacturing

• Use standard mouldings like Intrim’s inlay mould profiles to fit bespoke spaces

• Impress clients with seamless finishes on arches, staircases, or rounded feature walls

• Save time and cost by preparing mouldings on-site

 Common Mistakes to Avoid

• Using hardwood or dense profiles that resist bending

• Spacing kerf cuts too far apart (results in cracking)

• Not allowing for thermal expansion – especially in MDF if humid conditions

• Forgetting to pre-acclimate the material (allow 48 hours onsite)

• Over-sanding or cutting too deep, weakening the profile

 Recommended Tools for Kerfing

• Drop saw with guide

• Measuring tape or flexible radius gauge

• Brad nailer or pin nailer

• Flexible construction adhesive

• Sandpaper and filler

 Where to Use Kerfed Curved Mouldings

• Feature staircases

• Rounded hallways or corridors

• Arched window surrounds

• Circular rooms or towers

• Radius bulkheads and ceilings

 Order Curved Moulding Profiles from Intrim

At Intrim, we supply a complete range of mouldings suitable for kerfing, including inlay moulds, chair rails, wall battens, skirting and architraves. These products can be kerfed on site to a degree, to help you create smooth, seamless curves that elevate your designs.

For projects where a higher degree of precision or tighter radius is required, we also offer custom manufacturing of curved skirting and architraves. This is ideal for feature doorways, arched windows, or when kerfing isn’t practical due to material or design constraints.