How to Measure Windows for Secondary Glazing
Accurate measurements are crucial for a perfect fit. Follow our interactive step-by-step guide to measure your windows correctly and get accurate quotes.
Why Accurate Measurements Matter
Secondary glazing is custom-made to fit your specific windows. Even small measurement errors can result in:
- • Gaps that reduce thermal and acoustic performance
- • Units that don't fit properly or require expensive modifications
- • Delays in installation while new units are manufactured
- • Additional costs for remakes
Taking the time to measure carefully now will save you time, money, and frustration later.
What You'll Need
Essential Tools
- ✓ Steel tape measure (5m/16ft minimum)
- ✓ Notepad and pen
- ✓ Camera or smartphone
- ✓ Step ladder (for high windows)
Helpful Extras
- ✓ Spirit level (to check if frame is square)
- ✓ Flashlight (for dark recesses)
- ✓ Graph paper (for complex shapes)
- ✓ Assistant (to help with large windows)
Measurement Checklist
Complete these steps before requesting a quote
Common Mistakes to Avoid
× Measuring the glass only
Always measure the opening/recess, not just the glass pane
× Taking only one measurement
Windows are rarely perfectly square - always measure at multiple points
× Forgetting about handles
Window furniture can interfere with secondary glazing installation
× Using imperial when you meant metric
Be clear about units (mm or inches) and stick to one throughout
Pro Tips
Use a steel tape measure
Fabric tapes can stretch and give inaccurate measurements
Measure in millimeters
More precise than inches for custom-made products
Take photos
Pictures of the whole window, corners, and any obstructions help installers quote accurately
Measure twice, order once
Double-check all measurements before requesting quotes - mistakes can be costly
Next Steps
Once you've completed your measurements:
- Double-check all measurements
- Take clear photos of each window
- Use our cost calculator to get an estimate
- Request quotes from installers with your measurements and photos
- Professional installers will verify measurements during a site survey