Yes, reglazing a single-pane timber window is well within reach for a capable DIYer. It requires no licensed trade work, and with the right preparation and materials you can have a cracked or broken pane replaced in a day. That said, working with glass carries real safety risks, so take your time and follow the steps carefully.
What Is Reglazing?
Reglazing means removing a broken or damaged pane of glass from a timber window frame and fitting a new one, secured with glazing putty (also called linseed oil putty) and glazing sprigs (small metal pins). It's a traditional joinery skill that's been used on NZ homes for generations, and the materials are still widely available at hardware stores.
Tools and Materials You'll Need
- Safety glasses and heavy-duty gloves (non-negotiable when handling broken glass)
- Hacking knife or old chisel
- Putty knife or glazing knife
- Hammer
- Tape measure
- Glass cutter (if cutting your own pane — most glaziers or hardware stores will cut to size for you)
- Linseed oil glazing putty
- Glazing sprigs (also called glazing points or brads)
- Primer suitable for bare timber
- Exterior paint to finish
You'll find most of these at Bunnings or Mitre 10. For paint and primer, Resene and Dulux both offer products suited to exterior timber joinery.
Step-by-Step: How to Reglaze a Timber Window
1. Remove the Broken Glass Safely
Put on your gloves and safety glasses before touching anything. Carefully remove loose shards and place them in a cardboard box or thick newspaper — never a plastic bag. Use a hacking knife or old chisel to chip away the old hardened putty from the rebate (the groove in the frame that holds the glass).
2. Pull Out the Old Glazing Sprigs
Use pliers or the claw of a hammer to remove the small metal sprigs that held the old pane in place. These are easy to miss, so run your fingers carefully along the rebate once the putty is cleared.
3. Prepare the Rebate
Sand or scrape the rebate back to bare, clean timber. Apply a coat of primer and allow it to dry fully. This is an important step — unprimed timber will suck the oil out of your putty, causing it to crack and fail prematurely.
4. Measure and Order Your Glass
Measure the rebate opening carefully (height and width), then subtract about 3 mm from each dimension to allow for expansion and fitting tolerance. Standard 3 mm float glass is suitable for most single-pane windows. Have the glass cut to size at a glazing supplier or hardware store — this is usually inexpensive and far safer than cutting it yourself at home.
5. Bed the Glass in Putty
Knead your glazing putty until it's soft and pliable. Press a thin, even layer (about 3 mm) of putty into the rebate all the way around — this is called the back putty or bedding putty. Press the new pane of glass firmly into this bed, applying pressure at the edges (never the centre) until the glass sits evenly.
6. Secure with Glazing Sprigs
Hammer glazing sprigs into the timber frame every 150–200 mm around the pane, sliding the hammer flat against the glass surface. The sprigs should sit flush against the glass to hold it in place.
7. Apply the Face Putty
Press more putty into the angle between the glass and the frame, then use your putty knife at a 45-degree angle to form a neat, bevelled fillet. Smooth it with a damp finger or cloth. The putty should sit just below the sight line of the glazing bar so it won't be visible from inside.
8. Leave to Cure, Then Paint
Allow the putty to skin over for at least 7–14 days before painting. Apply a coat of exterior primer followed by your chosen topcoat, lapping the paint slightly onto the glass (about 2 mm) to seal the putty edge and prevent water ingress. Wattyl and Resene both offer suitable exterior trim paints.
A Note on Glass Types and Safety Glazing
If your window is in a critical location — such as beside a door, in a bathroom, or at low level where someone could fall against it — the NZ Building Code (specifically clause F4: Safety from Falling) may require safety glass (toughened or laminated). Check with your local council if you're unsure. Using standard float glass in a safety-glazing zone is a compliance issue and a genuine safety risk.
Does This Work Require a Building Consent?
Replacing a like-for-like single pane of glass in an existing window is generally considered maintenance work and is typically exempt from building consent under Schedule 1 of the Building Act. However, always confirm with your local council before starting, as exemptions can depend on the specifics of your situation. MBIE Building Performance has useful guidance on what work requires consent.
When to Call a Professional
Consider hiring a qualified joiner or glazier if:
- The window frame itself is rotted, warped, or damaged — this is joinery repair work beyond simple reglazing
- The pane is large, heavy, or awkward to handle safely on your own
- The window is at height and requires working off a ladder for extended periods
- Safety glazing is required and you're unsure of the specification
- You're dealing with heritage or character joinery where a poor result could affect the look of your home
A skilled local joiner can reglaze a window quickly and guarantee a weathertight result. You can find qualified joiners and glaziers in your area on tradedirectory.co.nz.
Safety Reminder
Glass injuries can be serious. Always wear cut-resistant gloves and eye protection when handling glass, dispose of broken glass responsibly, and never rush the job. If you're working at height, follow safe ladder practices as outlined by WorkSafe NZ.
