Calculating Rough Opening Sizes

First, we will determine the rough opening sizes. Rough openings may be specified by the manufacturer. Always verify dimensions, materials, and additional space for squaring.

“Squaring spacing” refers to extra space in the opening that will allow for door or window adjustments as necessary. 

To calculate the rough opening size, simply add the size of the door or window to the thickness of your bucking material as well as the squaring spacing. Additionally, doors will have 1 times the thickness of the bucking material added to the opening height because the bottom of a door typically isn’t bucked. Add 2 times the bucking thickness to the width.

Windows and framed door rough opening sizes should always be no less than half an inch wider and half an inch taller than the window or framed doors actual dimensions to allow the window or door to be plumbed square even if the opening moves slightly during construction of the walls. Doors that are not pre-hung must account for jamb sizes and shimming, plus the door height and width.