Replacing a broken timber louvre blade is one of the more satisfying DIY carpentry jobs a homeowner can tackle — it requires no special licences, minimal tools, and can usually be completed in under an hour. The key is getting the measurements right and sourcing timber that matches your existing blades as closely as possible.
Understanding How Timber Louvre Blades Work
Timber louvre windows use a series of horizontal blades (also called slats or louvres) held in place by a metal or plastic pivot clip at each end. The clips sit in a frame channel and allow the blades to tilt open and closed together via a linking rod or mechanism. When one blade breaks, it usually just pulls free from the clips — the mechanism itself is often undamaged.
Before you start, check whether the pivot clips are also cracked or missing. Replacement clips are available from hardware stores such as Bunnings or Mitre 10, and it pays to replace worn clips at the same time.
Tools and Materials You'll Need
- Tape measure and pencil
- Fine-tooth handsaw or drop saw
- Sandpaper (120 and 180 grit)
- Timber to match existing blades (see below)
- Exterior-grade primer and paint or clear finish
- Replacement pivot clips (if needed)
- Safety glasses
Step 1 — Remove the Broken Blade
Gently flex or slide the broken blade out of its pivot clips. Most clips have a small slot or lip that the blade end sits in — you may need to tilt the blade at an angle to release it. Take care not to bend or crack the clips. If a clip is seized, a flat-blade screwdriver can help ease the blade free without forcing it.
Keep all the pieces of the broken blade — they'll help you match the profile and length exactly.
Step 2 — Measure Carefully
Measure the length, width, and thickness of the old blade. Standard NZ timber louvre blades are commonly around 75–100 mm wide and 12–19 mm thick, but this varies by window manufacturer and age. Also note the end profile — many blades have a slightly rounded or chamfered edge that fits into the clip.
Write down all three dimensions before heading to the timber merchant or hardware store.
Step 3 — Source Matching Timber
For interior louvre windows, clear pine or radiata pine is the most common timber used in NZ homes. For exterior-facing louvres, you'll want a more durable species — macrocarpa, cedar, or treated pine are good options, as they cope better with moisture and UV exposure.
Try PlaceMakers or a local timber merchant for dressed (DAR) timber in the right dimensions. If you can't find an exact match in width, buy the next size up and rip it down on a table saw (or ask the merchant to do it for you).
Tip: If your louvre window is older, the blades may be imperial dimensions (e.g. 3 inches wide). Don't be surprised if metric stock is slightly narrower — check the fit in the clips before cutting to length.
Step 4 — Cut and Shape the New Blade
Cut the new timber to the exact length of the old blade using a fine-tooth saw. A clean, square cut is important so the blade sits flush in the clips. Lightly sand all faces with 120-grit paper, then finish with 180-grit for a smooth surface.
If the original blade had rounded or chamfered ends, replicate this with sandpaper or a block plane so the new blade fits the clips properly.
Step 5 — Prime, Paint, or Finish
Before fitting the blade, apply a primer coat and at least one topcoat of paint or clear finish to all surfaces — including the end grain. This is especially important for exterior louvres, where unprotected timber will absorb moisture and swell or rot quickly.
Match the finish to your existing blades as closely as possible. Resene and Dulux both offer a wide range of exterior timber paints and stains suitable for this purpose. Allow the finish to dry fully before fitting.
Step 6 — Fit the New Blade
Slide the new blade into the pivot clips, reversing the removal process. The blade should sit snugly without being forced. Test the louvre mechanism by tilting the blades open and closed — the new blade should move in unison with the others. If it's stiff, lightly sand the ends until it moves freely.
Checking for Weathertightness
Louvre windows can be a weak point for weathertightness, particularly in older NZ homes. Once your blade is fitted, check that the blades close tightly with no obvious gaps. If the window leaks air or water when closed, the seals or the overall frame may need attention — this is worth addressing to meet the spirit of the NZ Building Code requirements around weathertightness (Clause E2). BRANZ has useful guidance on maintaining timber windows.
When to Call a Professional
This job is not restricted work — no licence is required for a homeowner to replace a louvre blade. However, consider calling a qualified carpenter (you can find local tradespeople on tradedirectory.co.nz) if:
- Multiple blades are broken or the frame is rotted or damaged
- The louvre mechanism (linking rod or pivot assembly) is broken and needs repair or replacement
- The window frame itself is out of square or showing signs of structural movement
- You're unsure whether the window requires a building consent for any associated repairs (always check with your local council — most like-for-like repairs are exempt under Schedule 1 of the Building Act, but confirm before starting)
A Licensed Building Practitioner (LBP) should carry out any work that affects the weathertight envelope of the building. Check the LBP register to find a qualified professional.
