Fitting a replacement glass panel into an existing timber bead is a job many NZ homeowners can tackle themselves, provided the pane is small, the glass type is straightforward (such as standard 4 mm float glass), and the existing frame is in good condition. For larger panes, double glazing, toughened or laminated safety glass, or heritage joinery, it's worth calling a qualified glazier.
Safety First
Glass edges are razor-sharp and broken glass is a serious hazard. Before you start:
- Wear heavy leather gloves and safety glasses at all times.
- Wear sturdy closed-toe footwear.
- Clear the area below the window of people and pets.
- Dispose of broken glass wrapped in several layers of newspaper inside a cardboard box — never loose in a rubbish bag.
Check WorkSafe NZ for general guidance on working safely with glass and at height.
Tools and Materials You'll Need
- Replacement glass cut to size (see measuring tips below)
- Glazing tape or glazing putty (for timber frames, linseed oil putty is traditional; modern acrylic glazing compounds are also suitable)
- Timber or plastic glazing beads (reuse existing beads if undamaged)
- Hammer and nail punch, or brad nailer
- Flat pry bar or stiff putty knife
- Tape measure and pencil
- Utility knife
- Paintbrush and exterior primer/paint to touch up the rebate
You'll find glazing tape, putty, and basic tools at Bunnings or Mitre 10.
Step 1 — Measure the Opening Accurately
Before ordering glass, carefully remove the beads (see Step 2) and measure the rebate opening — the actual timber recess the glass sits in — in both width and height. Measure in at least two places in case the frame is out of square.
Deduct 3–4 mm from each dimension to allow for expansion and to make fitting easier. This is called the clearance gap. Write down your measurements and take them to your glass supplier, who will cut the pane to size. Always double-check before ordering — glass cut to the wrong size cannot be returned.
Glass type matters: Under the NZ Building Code, certain locations require safety glass (toughened or laminated) — for example, panels near doors, low-level glazing, bathrooms, and stairwells. Refer to MBIE Building Performance for guidance on NZS 4223 glazing requirements, or ask your glass supplier. Using the wrong glass type in a regulated location is a compliance issue.
Step 2 — Remove the Old Beads and Glass
- Use a flat pry bar or stiff putty knife to carefully lever the timber beads away from the frame. Work gently to avoid splitting them — you'll likely want to reuse them.
- Number each bead lightly in pencil so you know which goes where.
- Once the beads are off, the old glass (or remaining shards) can be carefully lifted out. Wear gloves throughout.
- Scrape away old glazing tape, putty, or sealant from the rebate using a putty knife. The rebate should be clean and dry before you fit the new glass.
- If the bare timber rebate is exposed, apply a coat of exterior primer and allow it to dry. This prevents moisture absorption and helps the putty or tape adhere properly.
Step 3 — Apply Glazing Tape or Back Putty
There are two common methods for bedding glass into a timber rebate:
| Method | Best For | Notes |
|---|---|---|
| Glazing tape (foam or rubber) | Modern joinery, quick jobs | Self-adhesive, consistent thickness, easy to use |
| Linseed oil putty | Traditional/heritage timber frames | Requires painting over once skinned; slower |
| Acrylic glazing compound | General use | Paintable, flexible, good weather resistance |
Apply your chosen material to the back rebate (the inner face the glass will rest against) before placing the glass. This is called back bedding and it seals out moisture from behind the pane.
Step 4 — Set the Glass
- Place plastic setting blocks (small plastic packers, available from glazing suppliers) on the bottom rebate, positioned roughly one-quarter of the way in from each corner. These support the glass weight and keep it centred.
- Carefully lower the new glass pane into the rebate, resting it on the setting blocks. Centre it so there is an even clearance gap on all sides.
- Press the glass gently but firmly into the back bedding.
Step 5 — Refit the Timber Beads
- Apply a thin bead of glazing tape or compound to the face of the glass where each bead will sit.
- Press each numbered bead back into position. Start with the top bead, then the sides, then the bottom.
- Secure with panel pins (small nails) or a brad nailer, nailing through the bead into the frame — not through the glass. Use a nail punch to set the heads below the surface.
- Wipe away any excess compound that squeezes out with a damp cloth.
Step 6 — Finish and Paint
Once the compound has skinned over (check the manufacturer's instructions — usually 24–48 hours minimum), paint the beads and any exposed compound with a good exterior timber paint. Resene and Dulux both offer suitable exterior timber paints. The paint film should lap slightly onto the glass to create a weathertight seal — about 2–3 mm is ideal.
When to Call a Professional
Contact a qualified glazier or Licensed Building Practitioner if:
- The pane is larger than about 0.5 m², or in a high or awkward location.
- The glass required is toughened, laminated, double-glazed, or patterned.
- The location may require safety glass under the NZ Building Code (NZS 4223).
- The timber frame is rotted, warped, or damaged — this may need repair before glazing.
- You're unsure about building consent requirements (most like-for-like glass replacements are exempt under Schedule 1, but always confirm with your local council).
A skilled glazier will have the right tools, access to commercial glass suppliers, and the knowledge to ensure compliance. You can find qualified local glaziers on tradedirectory.co.nz.
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