Fitting scotia moulding is one of the most rewarding DIY joinery jobs a homeowner can tackle. With a mitre saw (or a good mitre box), some patience, and the right technique, you can achieve a clean, professional-looking finish that neatly covers the gap between your skirting and floor — or between your cornice and ceiling. Here's how to do it properly.
What You'll Need
Gather your tools and materials before you start:
- Scotia moulding — pine or MDF, available from Mitre 10 or Bunnings
- Mitre saw or mitre box and hand saw
- Tape measure and pencil
- Coping saw (for internal corners)
- Nail gun or hammer and lost-head nails (40–50 mm)
- Nail punch
- Flexible gap filler or paintable caulk
- Sandpaper (120–180 grit)
- Safety glasses and hearing protection
Measure Up Carefully
Measure each wall individually — rooms are rarely perfectly square. Add about 10% to your total linear metreage to allow for waste from cuts and any mistakes. Write down each wall length and note which corners are internal (inside the room) and which are external (rare for scotia, but possible around a hearth or step).
Tip: Always buy a little extra. Running short mid-job means a trip back to the store and potential colour or profile mismatches if stock has changed.
Understanding the Two Types of Corners
Internal Corners — Use a Cope Joint
For internal corners, a cope joint gives a far better result than two mitres meeting. One piece runs square into the corner; the second piece is coped (shaped) to sit over the profile of the first.
- Cut the first piece square and nail it into the corner.
- On the second piece, cut a 45° mitre inward so the profile is revealed.
- Use a coping saw to cut along the revealed profile line, undercutting slightly (about 5°) so only the face edge makes contact.
- Test-fit and trim as needed with a file or sandpaper.
Cope joints move with the timber as it expands and contracts — important in NZ's variable humidity conditions.
External Corners — Use a Mitre Joint
For external corners, cut both pieces at 45° so they meet neatly at the corner point. Mark carefully, dry-fit before nailing, and use a dab of wood glue at the joint for extra strength.
Cutting Scotia — Step by Step
- Set your mitre saw to 45° for corner cuts, 0° for straight butt cuts.
- Orient the moulding correctly — scotia sits with one flat face against the wall and one flat face on the floor (or skirting). Keep this orientation consistent when cutting.
- Cut long, trim short — always cut slightly long first, test the fit, then trim a sliver at a time until it fits snugly.
- For long walls where you need to join two lengths, cut both ends at a shallow 45° scarf joint so the join is less visible. Position the join over a stud or solid backing if possible.
Nailing and Fixing
Scotia is typically fixed to the skirting or floor edge, not the wall, so it can move with the floor. Use lost-head nails or a brad nailer at appropriate centres. Angle the nails slightly downward into the skirting or floor edge. Punch the nail heads just below the surface with a nail punch.
Do not glue scotia to both surfaces — this can cause it to split as the floor moves seasonally.
Filling and Finishing
- Fill nail holes with wood filler or stoppings compound, allow to dry, and sand smooth.
- Run a thin bead of paintable flexible caulk along the top edge where the scotia meets the wall or skirting. This hides any small gaps and gives a crisp painted line.
- Prime bare timber or MDF before painting. MDF edges are especially absorbent — seal them well. Resene and Dulux both offer suitable water-based primers and trims paints for interior joinery.
- Apply two coats of trim paint for a durable finish.
Common Mistakes to Avoid
| Mistake | How to Avoid It |
|---|---|
| Mitreing internal corners | Use cope joints instead — they close up better over time |
| Fixing to both wall and floor | Nail to skirting/floor only so the floor can move |
| Cutting too short | Always cut long first, then trim to fit |
| Skipping primer on MDF | MDF soaks up paint — always prime, especially on cut ends |
| Ignoring out-of-square corners | Test with a digital angle finder or protractor and adjust your mitre angle |
When to Call a Professional
Scotia fitting is generally straightforward DIY work and does not require a building consent or a licensed tradesperson. However, consider calling a qualified joiner if:
- You have complex angles, curved walls, or heritage moulding profiles to match.
- You're working around stairs or elevated areas where fall risk is a concern — review safe working practices at WorkSafe NZ.
- The existing skirting or flooring needs repair before the scotia can be fitted.
A skilled joiner will work quickly and deliver a flawless result. You can find qualified local joiners and tradespeople on tradedirectory.co.nz.
