Success in custom window procurement starts with the tape measure. A discrepancy as small as 1/4" can lead to a window that is either impossible to install or requires massive adjustments to the structural opening. Follow this professional blueprint to ensure your order fits perfectly the first time.
Identify the Rough Opening (RO)
The "Rough Opening" refers to the literal structural hole in your wall—the distance from stud to stud and header to sill. Do not measure your existing window frame, as it may be shimmed or out of square. If possible, remove the interior trim (casing) to reveal the actual structural framing.
The Triple-Measure Technical Protocol
Always take three measurements for both width and height to account for any bowing or settling of the house frame.
- Width: Measure at the top, middle, and bottom of the opening. Record the smallest number.
- Height: Measure at the far left, the center, and the far right. Record the smallest number.
- Depth: Ensure your wall thickness (e.g., 2x4 vs 2x6 construction) is compatible with the frame depth of the system you are ordering.
- The Diagonal Check: Measure from the top-left corner to the bottom-right, and from the top-right to the bottom-left. If the two numbers are different by more than 1/4", your opening is out of square and may require additional shimming during installation.
Pro Tip: When ordering, specify if your measurements are for the "Rough Opening" or the "Finished Frame Size." Our RO Calculator tool can handle the offsets for you automatically.
