How to measure for a commercial roll-up door.

Step 1: Measure the finished opening width

Measure between the inside faces of the finished jambs. Take a reading near the top, middle and bottom. If those numbers differ, note all three and call before ordering.

Step 2: Measure the finished opening height

Measure from the finished floor to the underside of the finished header. Check both sides of the opening so a sloped floor or header is not missed.

Step 3: Check that the opening is square

Confirm that the jambs are plumb and that the floor and header are level. A door can be the correct nominal size and still operate poorly if the guides are mounted out of parallel.

Step 4: Measure side room and headroom

The guides need clear mounting space on both sides, and the barrel needs room above the opening. Note beams, pipes, lights or electrical work in those areas. A hood needs 2 inches of extra side room and headroom.

Common measuring mistakes

• Measuring the old door instead of the finished opening.
• Taking only one width or height measurement.
• Ignoring out-of-plumb jambs or an uneven floor.
• Forgetting to identify whether the jambs are wood, steel or masonry.
• Ordering before verifying side room and headroom.