Rough opening
The rough opening is the framed hole in the wall, before trim, where a window or door is set.
The rough opening is built from studs, a header and a sill plate. It is always a bit larger than the window or door frame so the installer can set the unit plumb and level, then shim and seal it. Common practice leaves a small gap on each side.
If you replace a unit, the existing opening may not match the new product. Measure the opening, not the old frame. Wrong sizes cause delays and leaks. Our post on rough opening vs frame size explains how the two compare. Proper flashing around the opening keeps water out, and the jamb lines the sides.
Related terms
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Send your plans or a few photos of the openings. We will help you choose the system, the brand and the glass.