Step-by-Step Guide to Measuring
Proper measurements ensure that your windows and doors fit perfectly, minimizing gaps and enhancing energy efficiency, insulation, and security.
Step 1
Prepare Your Tools
Tape measure (preferably in millimeters for accuracy)
Notepad or phone for recording
Spirit level (optional for checking alignment)
Step 2
Measure the Width and Height
For the opening
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Take 3 measurements each for width (top, middle, bottom) and height (left, center, right).
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Use the smallest measurement in each category (width/height) for your final dimension
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Subtract 10–15mm (0.4–0.6 inches) from each side to leave room for installation foam and insulation
This helps account for any irregularities in the wall or masonry
For the replacement
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Measure both interior and exterior.
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If the difference between the two exceeds 30mm (1.2 inches), consult our team for precise recommendations
Step 3
Consider Floor Finishes (for Doors)
If the floor will be raised with tiles, screed, or insulation, subtract the thickness of those materials from your height measurement
This avoids issues with clearance or fitting after installation
Step 4
Determine Opening Direction
Windows/doors open left if hinges are on the left and handle on the right (when facing the window from inside)
Measuring Tips
Always measure twice to confirm
Note every measurement
Work in millimeters for more accuracy
Consult LexFenster Ireland if you're unsure or spot irregularities