Rough opening for 36 inch Door
The rough opening for a 36-inch pre-hung door is 38.5 inches by 82 inches. This means that the width of the frame should be 1 inch wider than the door itself and the height should be 3/4 of an inch taller than the door. Additionally, it is recommended that the rough opening should be at least 2 inches wider than the frame and 2-1/2 inches taller than the door.
