How to Measure Width
Measure the opening width at the TOP (left to right)
Measure at the MIDDLE
Measure at the BOTTOM
Critical Rule
Use the SMALLEST measurement!
Walls are rarely perfectly straight. The smallest width ensures your window will fit. We allow 5mm clearance on each side for installation.
Complete Measurement Process
Gather Tools
- Steel tape measure (not cloth)
- Pencil and paper
- Spirit level (optional)
- Smartphone for photos
Measure Width
- Measure at the top, middle, and bottom of the opening
- Record all three measurements in millimeters (mm)
- Use the SMALLEST measurement for your order
Measure Height
- Measure at the left, center, and right of the opening
- Again, record all three measurements
- Use the SMALLEST measurement
Measure Wall Depth
- Measure from inside wall to outside wall
- This determines frame size and installation method
- Standard depths: 115mm, 125mm, 145mm
Check for Square
- Measure diagonals from corner to corner
- If measurements differ, note it in comments
- We can manufacture to fit non-square openings
Minimum Gap Requirements
| Location | Minimum Gap | Recommended | Notes |
|---|---|---|---|
| Between windows (side by side) | 50mm | 75mm | Allows for proper installation and thermal expansion |
| Between window and wall corner | 100mm | 150mm | Required for corner cleats and structural integrity |
| Above window (lintel) | 50mm | 75mm | Space for leveling and fixing |
| Below window (sill) | 30mm | 50mm | For drainage and slope |
| Between combination windows (stacked) | 75mm | 100mm | Allows for mullion profile |
Important: These gaps are essential for proper installation, thermal expansion, and structural integrity. Never reduce below the minimum specified.
Common Measuring Mistakes
Measuring the old window frame instead of the opening
Always measure the masonry opening, not the existing frame
Using the largest measurement
Always use the smallest width and height for a perfect fit
Forgetting to measure wall depth
Frame depth must match your wall thickness
Not checking for level
Unlevel openings require custom trapezoid shapes
Not Sure About Measurements?
Our certified technicians can visit your site and take professional measurements. It's free and you get a guaranteed perfect fit.
Download Resources
Tools You'll Need
Steel tape measure
5m minimum, 8m recommended
Spirit level
To check for plumb and level
Notepad & pencil
Record all measurements
Smartphone camera
Take photos of the opening
Photo Tips for Better Accuracy
Overall View
Take a photo of the entire wall showing the window in context
Close-ups
Photograph corners, any damage, or unusual features
With Scale
Include a tape measure in photos for reference
Frequently Asked Questions
What if my opening is not square?
We can manufacture trapezoid or custom-shaped windows. Just measure all four sides and diagonals, and note the differences.
Can I install the window myself?
We always recommend professional installation for warranty coverage. Our team ensures perfect fit and sealing.
What happens if my measurements are wrong?
If you book our professional measurement service, we guarantee perfect fit. For DIY measurements, we'll verify with you before production.
Do I need to remove old windows first?
No, measure the masonry opening with the old window in place. We'll size the new window accordingly.