What does the abbreviation "R.O." signify on architectural plans?

The abbreviation "R.O." on architectural plans signifies "Rough Opening." This term refers to the designated space in a wall for a window, door, or other structural elements, prior to the finishing work that will frame these elements. The rough opening is crucial for ensuring that the installed product fits correctly within the wall and allows for any necessary adjustments during installation.

Understanding rough openings is essential for contractors and builders, as they provide the measurements needed to properly fit doors and windows. Specifications for rough openings usually include not just the size (width and height) but also the recommended clearance needed to allow for shimming, sealing, and proper installation of the finishing trim.

The other options, while related to construction, do not accurately reflect the meaning of "R.O." in this context.