All measurements should be in feet and inches. Step 1, measure across the existing door or desired space for the width, then up and down for the height. The rough opening of your space should be the same size as the door. Step 2, measure the sideroom, which is the space beside your door. Measure the width of the left side, and then the width of the right side. Step 3, measure the space above the door, which is called the headroom. Measure the height of the distance between the top of the door opening and the ceiling. Step 4, measure the ceiling, which is called the backroom. You’ll need to measure the distance of the garage door opening toward the back wall of your garage. You should have 6 total measurements in all once you’ve finished measuring the space. Keep in mind that having an automatic garage door opener installed might call for additional backroom or ceiling space.
A standard double garage door is 7 ft. high by 16 ft. wide. Standard single doors are 7 ft. high by 8 or 9 ft. wide. Because the doors are so large, few home centers and only some garage door stores keep many doors in stock, so expect to order one instead of buying it off the shelf. Garage doors are available in wood, fiberglass and steel. Steel doors, like ours, are light, maintenance-free, affordable, readily available, and have an insulating value as high as R-19.