Do You Know Anything about Door Gap Gauges: Read Here

This could be the first time you hear about a door gap gauge, and we don’t fault you for that. It’s not a common item people talk about in regular conversations. Here’s the down-low on this handy device that could save lives.

A fire door gap gauge is a simple tool fire door industry inspectors use to measure and check the clearance requirements per the NFPA 80 code. Clearance requirements are the most common problem on fire doors. The gap measuring gauge will speed up your fire door inspections, is more accessible than a tape measure, is compact, and is easy to use. The gap gauge is too valuable to do without.

This extremely efficient device is an “essential” product for every fire marshal, AHJ/IOR, and maintenance supervisor responsible for complying with compartmentalization ordinances. Its compact form allows you to quickly and accurately confirm compliance, whether for fire safety or energy conservation.

What They Do

With a door gap gauge, you can evaluate the gap in a door and make adjustments to maintain tolerances. The device is one of the most efficient tools on the market, saving construction workers time examining door gaps to maintain compliance with ADA requirements or prevent unnecessary non-compliances. Crews use a gap gauge to adjust door thresholds and jambs so workers will not have to return to fix the doors.

Door Gap Gauge Maintenance

  • Determine your door and frame types during inspection for proper NFPA 80 compliance: 
  • For swinging steel doors, the distance between the top, the door edge, and the frame edge shall not be less than 1/8’’. 
  • For swinging wood doors in pairs, the distance between the leading and vertical edges of each entry, pair of doors, and the frame shall not be less than 1/8’’.
  • The clearance at the bottom of a door and any non-combustible surface should not exceed three-quarters of an inch.
  • The clearance underneath the bottom of a door and raised non-combustible sills should be no more than three-eighths of an inch.
  • Determine the door gap: Remember to keep track of all clearances when opening and closing the door to note them when your annual NFPA 80 inspection.
  • Place the fire door gauge on a hard, flat surface. 
  • Then lay the door gap gauge along the gap between the door and the frame, as far as it will go. The door gap gauge should fit precisely, with a tight seal between the two sections.
  • Grab your gauge, find the size of the gap, then insert the device into the space between the floor and door. Take an accurate measurement.
  • Confirm that your door gap gauge reads the gaps between the doors and the floor fall within the clearances outlined in NFPA 80
  • For more help, download our free NFPA 80 Fire Door Inspection checklist and use it on your projects.


Shop owners should conduct annual fire door inspections and invest in needed maintenance, including dampers, walls, and fire-stopping systems. These regular checks and use of door gap gauges make customer life more convenient, safe, and compliant with safety standards.

Learn more about door gap gauges at All Things Inspector! We have the inspection tools that you need and more. Visit our website now!

Keep reading

Related Article

What are the ADA toilet clearance requirements

Toilets and bathrooms must be made accessible for everyone including disabled and handicapped people. ADA requirements are based on the needs of disabled persons. These