Builders and property managers have many responsibilities to ensure their building remains accessible to the public. It’s vital to check the door gap clearance and other factors to ensure doors are easy to open or that fire can’t quickly spread. The fastest, most accurate way to check if a door is NFPA 80 compliant is to use a door gap gauge from All Things Inspector.

What is a Door Gap Gauge?

The Door Gap Gauge is an easy-to-use tool that makes checking a door gap fast and straightforward. This highly efficient tool is a "must-have" item for every inspector, fire marshal, commercial property/maintenance manager, and fire department needs in their toolbox. It's perfectly sized and marked to measure the gap size for a door quickly.

Our door gap gauge was designed with input from fire marshals, building inspectors, and accessibility experts. The result is a tool that’s accurate, easy-to-use, and inexpensive. These factors have helped the door gap gauge from All Things Inspector gain popularity, and you can find them in use across the United States.

See our extensive inventory of door gap gauges

The Door Gap Gauge is a simple to use, highly efficient “must have” tool that every inspector, fire marshal, commercial property/maintenance manager and fire department needs in their toolbox. The door gap gauge has gained popularity and can be found in use across the United States

Buy Door Gap Gauges Online

With a single door gap gauge, you can check the clearance of a door in under a minute. The device more than pays for itself with the time it saves workers who are checking door clearances. Plus, by ensuring doors have correct margins, building owners can avoid costly penalties for noncompliance. Building crews can use door gap gauges to prevent issues that would require the team to come back to fix the doors.

You can buy a single door gap gauge from All Things Inspector if it's for an individual building inspector or property manager. However, you can also save money by getting multipacks with between two and six gauges. A team of workers armed with door gap gauges can quickly check all of the doors in a high-rise office, hospital, apartment complex, or any facility that has many fire doors that need to be checked.

How How to Use A Door Gap Gauge.

All Things Inspectors Door Gap Gauge can be used to measure gaps on fire-rated and If you need to learn how to use a door gauge.non-rated door assemblies with any style door. Whether the door and frame are of hollow metal, wood, aluminum or fiberglass construction.

Below we outline how to use the Door Gap Gauge.

Step 1 Figure out what type of door and frame you are inspecting to pinpoint the required NFPA 80 requirements.

Top and Vertical Edge of Door Requirements:

  • For Steel Doors Swinging in pairs the clearance between the top and the vertical edges of the door, the frame, and the meeting edges shall be 1/8″ – 1/16″.
  • For Wood Doors Swinging in pairs the clearance between the top and vertical edges of the door, the frame and the meeting edges shall not exceed 1/8″.

Bottom of Door Requirements:

  • The clearance under the bottom of a door and non-combustible surface where no sill exists shall be a maximum of 3/4″.
  • The clearance under the bottom of a door and raised non-combustible sills shall be a maximum of 3/8″.

Now that you know the clearance requirements you are trying to measure you will move on to Step 2.

Step 2 Measure the gaps
Note: Measure all clearance dimensions on the pull side of the door

Measuring the Top and Vertical Edge of Door Requirements:

  • Grab you gauge and locate the step portion of the gauge with the dimension that you are looking to measure.
  • Place the gauge in your hand so you can insert the gauge between the door and the frame. The gauge should fit in the gap between the door and the frame, sliding along the entire length of the gap along the top and vertical edges.

Measuring the Bottom of Door Requirements:

  • Grab you gauge and locate the step portion of the gauge with the dimension that you are looking to measure.
  • Place the gauge in your hand so you can insert the gauge under the bottom of the door and take an accurate measurement.

Step 3 Verify that your door gaps fall within the required min and maximum requirement as required by NFPA 80 and adjust as required.

Step 4 If you still need some guidance we have a couple of how to use a door gap gauge videos that you can watch.

Step 5 Reference below the Fire Door Inspection Checklist that we have put together for maintaining fire door compliance per NFPA 80. We have also put together a Door Inspection Form for you to download.

Download All Things Inspectors Door Inspection Form

  1. Check door leaf and frames for fire door labels and make sure that they are legible.
    • Make sure the labels are legible. The door leaf label should be attached to the hinge edge of the door just below the top hinge or at the top edge of the door. A second label should be on the frame. If the labels are missing or painted over, the Authority Having Jurisdiction (AHJ) may require them replaced.
  2. Look for open holes/breaks in the door or frame.
    • Look for holes from missing, removed or incorrect fasteners.
  3. Make sure glazing, glazing beads and vision light frames are intact and securely fastened in place, if so equipped.
    • Tighten loose and replace missing fasteners. Ensure that all glazing is labeled for the fire resistance of the opening.
    • The glass should be free from damage and cracking?
    • Make sure that the glazing is fire-rated and labeled accordingly.
  4. Check that the door, frame, hinges, hardware, and non-combustible thresholds are secure, aligned and are in working order.
    • Verify that the face of the door is flush or slightly inset with the edge of the frame. Check that the top and bottom flush bolts project one-half inch into the strike. Look for signs of damage. Realign or repair the damage.
  5. Inspect for missing, defective or broken parts.
    • During inspections, it is common that latch bolts, and strike plates, closer arms and cover plates have not broken.
  6. With the door closed, measure door clearances around the perimeter of the door from the pull side of the door to make sure the door clearances are within allowable limits.
    • On paired doors, without overlapping astragals, measure between the meeting stiles. The clearance under the bottom of the door is generally ¾” and the top and vertical reveals are 1/8” +/- 1/16”.  You should always look for wear and tear on the frame or the door. Wear more often than not indicates poor or miss-aligned margins.
  7. Open the door fully and confirm that the self-closing device is operational and completely closes and latches the door.
    • Adjust the self-closing device to achieve full closure and latching without exceeding 15 lbs. of opening force pressure.
  8. When a coordinator gets installed, confirm that the inactive and active leaves operate in the correct sequence (pairs only).
    • Open the door, then close it, observing whether the inactive leaf closes before the active leaf. If the door is not securely latching, evaluate whether it is a faulty latch bad coordinator or door misalignment.
  9. Check that the latching hardware operation secures the door when in a closed position from a self-closing position without additional help from a human.
    • Make sure that the latch secures the door in the closed position.
  10. Look for auxiliary hardware items or objects that interfere or prohibit fire door operation or closure
  11. Inspect for field modifications to the door assembly that void the fire door label.
    • Look for barrel bolts, deadbolts or kick down door holders. Remove non-compliant addons.
  12. Verify the presence and integrity of any required meeting edge protection, smoke gasketing.
    • Smoke gasketing cannot interfere with closing the door. Replace or repair as needed.
  13. Confirm that signage affixed to the door gets attached with adhesive.
    • Signage should not get attached with any mechanical fasteners or screws.
    • Signage cannot exceed five percent of the door surface.
  14. Hold Open Devices
    • Door hold opens are tied into the fire alarm and working as designed when they are required.
  15. Fire Exit Hardware
    • Make sure the hardware is Fire Exit Hardware as necessary
  16. Tools for inspecting fire-rated doors.
    • There are several useful tools for checking fire door clearances quickly and accurately (much better than using a tape measure and "eyeballing" it). Purchase a  fire door gap gauge today to make your work life more efficient.
    • The Fire Door Gap Gauge is the most innovative tool to make sure your fire-rated doors have the required clearance requirements per NFPA 80 on the market today.

Watch these videos to see how easy it is to use a door gap gauge to check compliance of a fire door.

Watch the door gap gauge video to see if the door gap is too big?


Watch the door gap gauge video to see if the door gap is too small?

If you have a fire rated door that you need to inspect.  You need to watch the video to see all the features the best door gap gauge boast.

Watch the door gap gauge video to see if the door gap is just right?