How to Replace a Broken Glass Pane in a Steel Window Frame

Learning how to replace a broken glass in a steel window frame requires a specific approach, different from working with aluminium or wooden frames. Steel windows are durable and stylish, but their hardened glazing compounds and rigid frames demand extra care during removal and installation.

This guide walks you through the safe and effective steps to replace a broken glass in a steel window frame, from removing old glazing to installing the new pane.

When Should You Replace the Glass?

You should replace a steel window glass pane if:

• The glass is cracked or shattered
• The putty is crumbling, loose, or falling out
• Water is seeping in due to gaps or failed glazing
• You’re upgrading to safety glass, double glazing, or frosted glass

Tools & Materials You’ll Need

• Replacement glass panel (cut to size)
• Measuring tape
• Putty knife or chisel
• Glazing compound or putty
• Glazier’s points or clips
• Heat gun (for softening old putty)
• Wire brush or sandpaper
• Glass cleaner and cloth
• Protective gloves and goggles

How to Replace a Broken Glass in a Steel Window Frame Step-by-Step

Step 1: Ensure Safety

• Wear safety gloves and goggles.
• Tape over the cracked glass to prevent pieces from falling during removal.
• Lay a protective cloth or drop sheet below the window.

Step 2: Remove the Old Glass Pane

• Carefully remove any loose shards by hand.
• Use a putty knife to remove surrounding glazing compound.
• For hardened putty, use a heat gun to soften it—do not overheat the steel frame.
• Extract any glazier’s clips or metal pins holding the pane in place.

Once the glass is removed, vacuum or brush out any leftover shards or debris.

Step 3: Clean the Frame

• Use a wire brush or sandpaper to clean the rebate (the inside edge of the steel frame).
• Remove all remaining bits of putty, dust, and rust.
• Wipe clean with a cloth and allow to dry before proceeding.

Step 4: Measure and Fit the New Glass Pane

• Measure the width and height of the frame opening and subtract 3mm to allow for expansion and installation.
• Ensure the new glass pane is cut to size and cleaned before fitting.

Step 5: Install the New Glass

• Place the glass into the frame opening.
• Use glazier’s points or clips to hold the glass securely.
• Press them in gently with a putty knife or screwdriver.

📌 For windows that flex, setting blocks may help align the pane evenly.

Step 6: Apply Fresh Putty

• Roll your glazing putty into thin ropes.
• Press it into the gap around the glass and frame.
• Smooth with a putty knife at a 45° angle for a neat bevel that directs water away from the window.

Allow the putty to cure—this may take a few days depending on the product.

Step 7: Paint the Frame (Optional but Recommended)

• Once the putty is cured, apply paint to protect the steel frame and putty from moisture and corrosion.
• Use a rust-inhibiting primer followed by weatherproof paint.

Tips for Long-Term Success

• Always allow time for the putty to cure before painting
• Avoid working in cold or wet weather, which affects putty adhesion
• Clean steel window frames regularly to prevent rust buildup
• Use laminated or safety glass if required by building code

When to Call a Professional

You should consult a glazier if:

• The steel frame is rusted through or structurally damaged
• You’re installing double glazing or energy-efficient glass
• The glass panel is large, elevated, or requires specialized equipment

Final Tip:

With the right tools and care, you can confidently replace broken glass in a steel window frame and restore both function and appearance to your window.