Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.
CLERA WINDOWS + DOORS · PATIO DOORS GUIDE
Measuring accurately for a patio door replacement ensures the new unit fits the existing rough opening without requiring costly structural modifications. Here is how to do it correctly.
What you need: a steel tape measure, a level, and a notepad.
1. Measure the width
Measure the width of the rough opening at three points: top, middle, and bottom. Record the smallest measurement — this is your working width.
2. Measure the height
Measure the height of the rough opening at three points: left side, centre, and right side. Record the smallest measurement — this is your working height.
3. Check for square and level
Use a level to check whether the floor at the threshold is level and whether the sides of the opening are plumb. Out-of-square openings require shimming during installation.
4. Note the door swing or slide direction
For sliding doors, note which panel is the operating panel (left or right hand). For French doors, note whether they swing inward or outward and which side is the active panel.
Replacement door units are typically sized slightly smaller than the rough opening to allow for shimming and levelling. Most manufacturers will walk you through measurements during a free in-home consultation to ensure accuracy before ordering.
Why Clera? Clera offers free in-home measurements as part of the quote process, so you never have to worry about ordering the wrong size.
← Back to
Vinyl Windows & Patio Doors Guide. Canadian-made since 1978 .
Free in-home estimates