Fitting a new glass pane into a timber bead window is a job many NZ homeowners can tackle themselves, provided the pane is a standard single-glazed size and you take proper precautions with glass handling. If the window is large, in a high-risk location (such as a door, low panel, or wet area), or requires safety glass under the NZ Building Code, you should engage a qualified glazier.
Understanding Timber Bead Windows
A timber bead window holds the glass in place using thin strips of timber (the beads) that are pinned or nailed around the inside of the rebate. Unlike putty-glazed windows, the glass in a bead window sits on a bed of glazing compound or silicone, and the beads are then pressed against the glass to secure it. This system makes glass replacement relatively straightforward.
Safety First
Glass is heavy, sharp, and unforgiving. Before you start:
- Wear cut-resistant gloves and safety glasses at all times.
- Use a glass suction lifter for panes larger than about 400 × 400 mm.
- Never carry glass flat — always carry it on its edge.
- Dispose of broken glass wrapped in newspaper inside a cardboard box, clearly labelled, so it is safe for rubbish collectors.
Check WorkSafe NZ for general guidance on safe manual handling.
What Glass Do You Need?
Before ordering glass, check whether safety glass is required. Under the NZ Building Code (in particular Clause F4 – Safety from Falling and related acceptable solutions), safety glass (toughened or laminated) is mandatory in certain locations — for example, panels within 500 mm of a door, low-level glazing, bathrooms, and stairwells. If you are unsure, check with your local council or a licensed glazier. Using standard float glass where safety glass is required is a Building Code breach.
For most standard window replacements, 3 mm or 4 mm float glass is typical in older NZ homes.
Tools and Materials You Will Need
- Tape measure and pencil
- Flat pry bar or chisel (for removing beads)
- Hammer and nail punch
- Putty knife or scraper
- Glazing tape or glazing compound (e.g. a neutral-cure silicone suitable for timber)
- Setting blocks (small rubber or plastic packers)
- Replacement glass (cut to size by your glass supplier)
- Panel pins or glazing sprigs
- Primer (if repainting bare timber)
- Fine sandpaper
Step-by-Step: Fitting the Glass
1. Remove the Old Beads and Glass
Using a flat pry bar or chisel, carefully lever the timber beads away from the frame, starting at a corner. Work gently to avoid splitting them — you may be able to reuse them. Number each bead with a pencil so you know where it came from. Once the beads are off, lift out the old glass.
2. Clean Up the Rebate
Scrape away any old glazing compound, silicone, or debris from the rebate (the channel the glass sits in). Sand back any rough timber and apply a coat of primer to bare wood — this prevents the timber from drawing oil out of any new compound and helps adhesion.
3. Measure for the New Glass
Measure the rebate opening height and width in at least two places each, as old frames are rarely perfectly square. Take the smallest measurement in each direction, then subtract 3–4 mm from each dimension to give a clearance gap. This gap allows for thermal movement and prevents the glass from binding in the frame. Write down your measurements and have the glass cut by a professional glass supplier — most hardware stores and glaziers offer this service.
4. Place Setting Blocks
Position two small setting blocks (rubber or plastic packers, typically 3 mm thick) on the bottom rebate, roughly one-quarter of the way in from each corner. These support the glass off the timber and ensure the weight is distributed correctly, preventing the glass from resting directly on the frame.
5. Bed the Rebate
Apply a continuous bead of glazing tape or a compatible glazing compound around all four sides of the rebate. This creates a weathertight seal between the glass and the frame. For timber windows, a neutral-cure silicone or a traditional oil-based glazing compound both work well — check the product is suitable for timber and glass. Brands like Sika offer suitable sealant products.
6. Fit the Glass
With a helper if the pane is large, carefully lower the glass into the rebate, resting it on the setting blocks. Press it gently but firmly into the bedding compound. Check it sits squarely and that the clearance gap is even on all sides.
7. Refit the Beads
Press the timber beads back into position in the same order you removed them. Secure with panel pins or glazing sprigs, punching the heads just below the surface. Take care not to crack the glass by hammering too close to it — work along the bead gradually rather than fixing one end fully before the other.
8. Seal and Finish
Run a small bead of paintable sealant or glazing compound along the joint between the bead and the glass on the outside face if needed, and tool it smooth. Once cured, paint the beads to match the frame, lapping the paint slightly onto the glass (about 2 mm) to create a weathertight seal.
When to Call a Professional
Call a qualified glazier if:
- The pane is larger than you can safely handle alone.
- Safety glass is required under the Building Code.
- The window is double-glazed — DGU (double-glazed unit) replacement is a specialist job.
- The timber frame is rotten or damaged — a joiner or Licensed Building Practitioner should assess and repair the frame first.
- The window is in a heritage or character home with non-standard glazing.
You can find qualified local glaziers on tradedirectory.co.nz.
Window & Glass Association
