Fitting architraves around a door is one of those finishing jobs that can make or break the look of a room. Done well, neat trim gives your doorway a clean, professional appearance; done poorly, gaps and misaligned mitres will catch the eye every time you walk past. This guide walks you through the best way to measure, cut, and fix door trim in a typical New Zealand home.
What Are Architraves and Why Do They Matter?
Architraves (also called door trim or casing) are the decorative mouldings that frame a door opening, covering the gap between the door lining (jamb) and the wall lining — usually GIB plasterboard in modern NZ homes. They serve both a practical purpose (hiding the rough junction) and an aesthetic one (tying the room's style together).
Tools and Materials You'll Need
Before you start, gather the following:
- Tape measure and pencil
- Mitre saw (a compound mitre saw gives the cleanest cuts) or a mitre box and hand saw
- Nail gun (brad nailer, 18-gauge) or hammer and lost-head nails
- Construction adhesive (e.g. Sika or a grab adhesive)
- Architrave moulding of your choice — available at Mitre 10 or Bunnings
- Caulking gun and paintable acrylic sealant
- Sandpaper (120–180 grit)
- Nail punch and filler
- Spirit level
Step 1: Mark the Reveal Line
The reveal is the small setback between the edge of the door lining and where the architrave sits — typically around 6–8 mm. Use a combination square or a small offcut to mark a consistent reveal line all the way around the lining on both sides of the door. This line is your guide for positioning the trim.
Step 2: Cut and Fit the Head (Top) Piece First
Start with the horizontal head piece across the top of the door:
- Hold the architrave against the reveal line and mark where the mitre cuts need to start at each top corner.
- Cut 45-degree mitres at each end — the long point of the mitre should align with your reveal mark.
- Dry-fit the piece to check the mitres sit flush before fixing.
Tips for clean mitres
- Always cut slightly long and sneak up on the final fit.
- If your wall or lining isn't perfectly square (common in older NZ homes), you may need to adjust the mitre angle slightly.
- A sharp blade makes all the difference — replace dull blades before starting.
Step 3: Fix the Head Piece
Once you're happy with the fit:
- Apply a thin bead of construction adhesive to the back of the architrave where it contacts the lining and the wall framing.
- Nail through the architrave into the door lining with 50–60 mm nails, and into the wall framing or nogging behind the plasterboard with longer nails (65–75 mm).
- Use a nail gun for speed and consistency, or hand-nail carefully to avoid denting the timber.
- Punch all nail heads just below the surface.
Step 4: Fit the Side Legs
With the head piece fixed, move to the vertical side pieces (legs):
- Hold each leg in position against the reveal line, with the top mitre tight against the head piece mitre.
- Mark the bottom cut — legs typically sit on top of the floor or on a small plinth block if you have skirting boards to deal with.
- Cut the bottom square (90 degrees) and fix the same way as the head piece — adhesive plus nails into the lining and framing.
Dealing with skirting boards
Where the architrave meets the skirting board, you have two common options:
- Scribe/mitre the junction so they meet neatly at 45 degrees.
- Use a plinth block (a small square block at the base of the architrave) — this is a traditional NZ detail that avoids the need for a tricky mitre.
Step 5: Secure the Mitre Joints
Mitre joints can open up over time as timber moves with NZ's seasonal humidity changes. To prevent this:
- Apply a small amount of PVA wood glue into the mitre joint before final fixing.
- Drive a nail through the face of the head piece into the top of the leg at the mitre to lock it together.
- Wipe away any excess glue immediately.
Step 6: Fill, Sand, and Seal
- Fill all nail holes with interior wood filler and allow to dry.
- Sand filled areas smooth with 120–180 grit sandpaper.
- Run a neat bead of paintable acrylic sealant along the back edge of the architrave where it meets the wall. This prevents paint from cracking at this junction and stops draughts.
- The architrave is now ready for priming and painting — Resene and Dulux both offer excellent trim paints suited to NZ conditions.
Common Mistakes to Avoid
| Mistake | Why It's a Problem | Fix |
|---|---|---|
| Skipping the reveal line | Architrave looks uneven | Always mark a consistent reveal first |
| Nailing only into plasterboard | Trim will pull away over time | Nail into framing and lining |
| Ignoring timber movement | Mitres open up | Use glue at joints and seal edges |
| Cutting all pieces before dry-fitting | Wasted timber | Fit and check each piece before cutting the next |
| No sealant at wall junction | Paint cracks, draughts get in | Always caulk the back edge |
When to Call a Professional
Fitting architraves is generally a DIY-friendly job, but there are times when it pays to bring in a qualified carpenter:
- Structural door alterations — widening or moving a doorway involves framing work that may require a Licensed Building Practitioner (LBP) under the NZ Building Code.
- Complex profiles or heritage homes — matching intricate Victorian or Edwardian mouldings takes specialist skill and tooling.
- Large-scale renovations — if you're trimming out an entire house, a professional will be faster and deliver a consistent result.
You can find qualified local carpenters and joiners on tradedirectory.co.nz — always check they hold the relevant LBP licence for structural work.