Removing a broken glass pane from a timber frame is a task most handy homeowners can tackle safely — but only with the right protective gear and a methodical approach. Rushing or skipping safety steps is how serious cuts happen, so take your time and follow the process below carefully.
Safety First: What You'll Need
Before you touch any glass, gather your personal protective equipment (PPE). This is non-negotiable:
- Heavy-duty leather or cut-resistant gloves — standard garden gloves are not sufficient
- Safety glasses or goggles
- Sturdy closed-toe boots (steel-capped if you have them)
- Long sleeves and long trousers to protect your arms and legs
- A dust mask if the window is old and may have lead-based putty (common in NZ homes built before the 1970s — see the lead paint note below)
Also prepare your work area: lay down a drop sheet or thick cardboard beneath the window to catch falling glass, and keep children and pets well away from the area.
Lead putty warning: Older NZ homes may have glazing putty that contains lead. If you suspect this, do not sand or grind the putty dry. Dampen it before removal and dispose of waste carefully. Check WorkSafe NZ for guidance on working safely with lead-containing materials.
Step 1: Score and Stabilise the Broken Pane
If the glass is cracked but still largely in place, apply wide masking tape or duct tape in a cross-hatch pattern across the surface. This holds loose shards together and reduces the risk of pieces falling unexpectedly while you work.
If the pane is already badly shattered, skip the tape and move straight to careful removal.
Step 2: Remove Loose Shards by Hand
Working from the top of the frame downward, use your gloved hands to carefully wiggle and remove any large loose pieces of glass. Place them immediately into a sturdy cardboard box or a dedicated glass disposal bin — never a standard rubbish bag, which can be punctured.
For stubborn pieces still held by putty or glazing beads, use pliers (not bare hands) to grip and gently rock them free.
Step 3: Remove the Glazing Putty or Timber Beads
Timber frames are typically glazed in one of two ways:
Putty-Glazed Frames
Older sash windows and many traditional NZ timber frames use linseed oil putty. Once the glass is out, use a hacking knife (a stiff-bladed glazing chisel) or an old wood chisel to carefully chip away the hardened putty. Work at a low angle to avoid gouging the timber rebate. A heat gun on a low setting can soften stubborn putty, but take care not to scorch the timber.
Bead-Glazed Frames
More modern timber frames use timber or plastic glazing beads pinned or clipped around the glass. Use a putty knife or flat pry bar to gently lever the beads away from the frame, starting at a corner. Label or set the beads aside if you plan to reuse them.
Step 4: Clean Up the Rebate
Once all glass and putty are removed, use a stiff brush to sweep out the rebate (the groove the glass sits in). Remove any remaining glazing points (the small metal clips used to hold glass in putty-glazed frames) with pliers or a screwdriver. Sand the rebate lightly if needed, and check the timber for rot or damage — this is a good time to treat or repair it before re-glazing.
Step 5: Dispose of Glass Safely
NZ councils have varying rules on glass disposal. Generally:
- Wrap broken glass in several layers of newspaper, then place it in a sealed cardboard box labelled "BROKEN GLASS"
- Do not place loose glass in your kerbside recycling bin — it is a hazard for collection workers
- Check your local council's website or transfer station for specific guidance
Measuring for Replacement Glass
Measure the width and height of the rebate opening (the clear opening inside the frame) with a steel tape measure. Standard practice is to deduct 3–4 mm from each dimension to allow for expansion and fitting clearance. Write down both measurements and take them to your glazier or glass supplier.
Note that certain glass types — including toughened (safety) glass, laminated glass, and double glazing units — must be cut and supplied by a professional glazier. Safety glass is required by the NZ Building Code in specific locations such as doors, low-level panels, bathrooms, and near stairs. Check MBIE Building Performance for the current requirements under NZS 4223 (Glazing in Buildings).
When to Call a Professional
Call a qualified glazier if:
- The broken pane is safety glass, double glazing, or a large pane — these require specialist handling and equipment
- The window is in a restricted location requiring compliant safety glass under the NZ Building Code
- You are unsure whether the putty contains lead
- The timber frame is rotted or structurally damaged
- You are not comfortable working at height (never lean out of an upper-storey window to remove glass)
- The window is part of a heritage or character home requiring specialist care
A licensed glazier will also ensure the replacement glass meets NZ Building Code requirements — important for insurance and future sale of your home. You can find qualified local glaziers on tradedirectory.co.nz.
Window & Glass Association
