Sash windows are traditional, beautiful fixtures in many homes. But like any part of the home, they experience wear and tear. Cracked or broken panes are a common problem, but fortunately, one that you can often fix yourself. Replacing a pane of glass in a sash window is a straightforward process that many homeowners can tackle with the right directions.

Pane Glass Sash Window

Safety Considerations

Before starting any work on your windows, consider the following safety precautions:

  • Gloves: Always wear thick work gloves to protect your hands when handling broken glass.
  • Safety glasses: These are essential to protect your eyes from potential shards or flying debris.
  • Sturdy workspace: Set up a stable and secure workspace to lay the sash for the repair process.
  • Secure the workspace: Clear away any children and pets before starting, and be mindful of loose debris that could be kicked up.

Tools and Supplies for Replacing a Pane of Glass in a Sash Window

Before you start replacing the glass pane in your sash window, gather these tools and supplies:

  • Replacement glass pane: Measure the opening carefully to ensure the correct size for your replacement window pane.
  • Tape measure: For accurate measurements.
  • Putty knife To remove the old glazing putty.
  • Hammer: For removing old glazing points and tapping in new ones.
  • Work gloves: For hand protection.
  • Safety glasses: For eye protection.
  • Glazing putty: Purchase fresh, pliable glazing putty.
  • Glazing points: To hold the new glass pane in place.
  • Paintbrush To apply primer.
  • Exterior wood primer: To treat bare wood before applying the new putty.

Removing the Damaged Glass and Preparing the Frame

  1. Remove loose glass: Carefully remove any loose pieces of broken glass from the window frame. If the pane is mostly intact, cover it with a cloth and gently tap it with a hammer to create controlled breaks and ease removal.
  2. Remove old putty: Use a putty knife or a flathead screwdriver to meticulously scrape away all remaining hardened glazing putty from the window frame. Take care not to gouge or damage the frame itself.
  3. Remove glazing points: Locate and pry out the glazing points, the small metal clips that secured the old glass pane in place. A screwdriver should suffice for this task.
  4. Clean and inspect: Thoroughly clean the rabbet (the groove in the frame where the glass rests). Inspect the wood or metal for any damage, rot, or deterioration. If necessary, repair or replace these sections before proceeding.
  5. Prime bare wood: If your window frame is wooden and you’ve exposed bare wood, apply a coat of wood primer to protect it and ensure a proper seal for the new glazing putty.

Measuring and Cutting the New Glass Pane

  1. Accurate measurements: Precisely measure the width and height of the opening in the window frame where the new glass will sit. To ensure a snug fit, subtract approximately 3mm from both width and height measurements. This allowance provides a slight gap for expansion and contraction of the glass due to temperature fluctuations.
  2. Glass supplier: Take your measurements to a local glazier or hardware store to have a replacement pane of glass cut to size. Standard single-strength window glass is typically 3mm thick and suitable for most sash window repairs.
  3. Cutting glass (advanced): If you are experienced in glass cutting, you may choose to cut the glass yourself using a glass cutter. However, for safety and accuracy, having a professional cut the glass is generally recommended.

Installing the New Glass Pane for Sash Window

  1. Apply bedding putty: Roll a small amount of glazing putty into a thin rope. Press this rope into the rabbet of the window frame, creating a bed for the new glass pane.
  2. Insert the glass: Carefully position the new glass pane into the prepared frame, ensuring it sits evenly within the rabbet. Gently press it into the putty to create a seal.
  3. Secure with glazing points: Use a putty knife to insert glazing points at regular intervals around the edge of the glass pane. Space them approximately every 15cm to hold the glass securely in place.

Sealing and Finishing with Glazing Putty

  1. Apply glazing putty: Take a generous amount of glazing putty and knead it until it’s soft and pliable. Roll it into long ropes and press it firmly along the edge of the glass where it meets the frame, creating a smooth, angled bead.
  2. Smoothing the putty: Use a putty knife to smooth the putty, creating a 45-degree angle that slopes away from the glass. This angle helps shed water and protect the seal. Take your time to achieve a neat and even finish.
  3. Allow putty to cure: Before painting, allow the glazing putty to cure completely according to the manufacturer’s instructions. Curing times can vary, but it typically takes several days to a week for the putty to harden fully.
  4. Painting (optional): Once the putty is cured, you may choose to paint the window frame to match the existing colour or give it a fresh new look.

Additional Tips and Considerations

  • Removing the sash: If possible, removing the entire window sash from the frame can make the glass replacement process considerably easier and safer. Consult online resources or a handyman if you are uncertain about how to remove your specific type of sash window.
  • Large or complex windows: For significantly large windows, windows with intricate designs, or if you don’t feel confident in your abilities, consider hiring a professional glazier for the repair.
  • Historic windows: If your sash windows are in a heritage-listed or period home, it’s advisable to consult a specialist who has experience in restoring historic windows to ensure that any repairs are done in a sympathetic manner.
  • Double-glazed sash windows: Replacing glass in double-glazed sash windows is generally more complex and best left to professionals, as ensuring the proper seal between the panes is vital for insulation.

When to Call a Professional

There are instances where it’s best to call in a professional glazier or window repair expert. Here are a few reasons:

  • Severe sash damage: Extensive damage to the wood of the sash frame or severe rot may require professional restoration.
  • Special glazing needs: Historic windows or windows with intricate glazing designs are often best left to experts.
  • Large areas of breakage: Replacing multiple large panes, especially in upper story windows, may need specialised equipment and safety knowledge.
  • Complex window types: If your sash windows are non-standard or have complex mechanisms, it might be best to seek professional help.

Benefits of Hiring a Professional to Replace a Pane of Glass in a Sash Window

You might want to fix a broken window yourself, but hiring a pro for sash window glass replacement is wise. Here’s why:

  • Expertise: Professionals possess the skills and knowledge for precise repairs, have access to the right materials, and prioritise safety.
  • Efficiency: Glaziers work quickly, saving you time and minimising household disruption.
  • Quality: They ensure proper fit, sealing, and insulation, restoring your window’s functionality and appearance.
  • Avoid Costly Mistakes: Prevent potential DIY errors that could lead to further damage and expensive repairs down the line.
  • Guarantees: Many professionals offer warranties on their workmanship, giving you peace of mind.

Replacing a pane of glass in a sash window requires some preparation and care, but it’s a task well within the reach of most homeowners. By following these instructions and carefully considering the project’s scope, you can restore your sash window and maintain a beautiful element in your home.