A rough opening is the opening in a wall prepared to receive a window or door unit. It is larger than the unit itself to leave room for positioning, shims and insulation. The rough-opening measurement is different from the size of the visible glass, the door panel or the finished opening after trim is installed.
In home addition planning, use the selected product’s specified rough-opening dimensions when reviewing drawings. Ask the project team to confirm the unit size and opening requirements together before framing or ordering. Avoid using a general rule for every window or door, because the required clearances depend on the product and installation. Clear measurements help the opening, unit and surrounding finishes fit together.