Why Should You Know The 20 Minute Fire Rated Door Requirements?

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What Makes a 20 Minute Fire Rated Door?

If you have an attached garage then you most probably have a garage entry door to the house. You also must be aware that, as per code, the garage entry door must be a 20 minute fire rated door. What is special about this door? What makes a 20 minute fire rated door?

A 20 minute fire rated door must slow or stop the spread of flames and smoke from the garage to the house for at least 20 minutes. The entire door assembly, including the door, the frame, the hardware and the components, must pass the test.

The actual material of the door, frame, hardware & components is not important. The door or frame material could be steel, wood, aluminum or fiberglass. Any material can be used as long as each individual item and the complete system meets the 20 minute fire rated door requirements.

The tests must be conducted by a certified, independent test facility in accordance with the test parameters laid out by Underwriters Laboratory (UL)

20 Minute Fire Rated Door Requirements

The entire door assembly specimen is exposed to a standard fire exposure controlled to achieve specified temperatures throughout a specified time period, followed by the application of a specified standard fire hose stream. 

To be approved as a 20 minute fire rated door, the assembly must stay intact in the frame and the flames should not reach the other side. However, the standard fire hose stream test is not applicable for a 20 minute rating.

While the actual fire scenario will vary from case to case, the test provides a relative measure of fire performance of door assemblies under these specified fire exposure conditions.

What Is the Difference Between UL 10B and UL 10C?

The difference in the method of testing between UL 10B and UL 10C is that

UL 10B Test

During the UL 10B test, Fire Tests of Door Assemblies, the neutral pressure plane is maintained near the top of the fire door assembly.

Image Credit: REEB Learning Center

UL 10C Test

During the UL 10C test,  Positive Fire Pressure Tests of Door Assemblies, the neutral pressure plane is maintained at a height of 40” from the floor. This produces conditions that are more similar to what occurs during a structure fire.

Image Credit: REEB Learning Center

The International Building Code (IBC) requires that fire rated doors be tested as per UL 10C or NFPA 252 (Standard Methods of Fire Tests of Door Assemblies).

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Do Fire Rated Doors Need Fire Rated Frames?

The test method, whether UL 10B or UL 10C is always conducted on the “fire rated door assembly”, not just the door. The assembly comprises of

  1. Door
  2. Glass Panels in the Door
  3. Transom & Sidelight Assemblies
  4. Door Frame
  5. Builders / Exit Hardware
  6. Hinges
  7. Latching / Closing / Hold Open Devices

The opening between the garage and the house must be equipped with a door that provides protection As per Section R302.5.1 of the 2018 edition of the International Residential Code (IRC) some other 20 minute fire rated door requirements are:

  • Must be self-closing or automatic closing
  • Must be positive latching
  • Must remain closed during a fire

Make sure that you purchase and install a complete 20 minute fire rated door assembly that meets all the requirements. You can ensure that by checking the labels.

Do 20 Minute Doors Require a Label?

Yes. One of the 20 minute fire rated door requirements is that all components are labeled, at specific locations, to state the fire rating. The labeling agency must also put their logo on each label for traceability. The labels are to be affixed to the components of the fire rated door assembly as under:


Label must be located on the edge of a door between the top and middle hinges.

Door Frame

Label must be located on the frame rabbet between the top and middle hinges.

The label is to satisfy you that the 20 minute fire rated door meets the requirements. Bear in mind that the label is unlikely to survive an actual fire.

NOTE: Above information has been obtained from STEEL DOOR INSTITUTE BLOG


In conclusion I would like to say that knowing and understanding the 20 minute fire rated door requirements is extremely important. You want to make sure that you are in compliance with the code.

More importantly a correctly installed 20 minute fire rated garage entry door could save lives in case there is a fire in your attached garage. Keep the following in mind when it comes to the fire rated garage entry door:

  1. A 20 minute fire rated door actually means a 20 minute fire rated door assembly.
  2. Each component, such as door, door frame, hardware, glass panels if any, etc., must be tested and labeled for a rating of 20 minutes or more.
  3. Tests must be done by independent agencies according to UL 10C or NFPA 252 test procedures.
  4. The fire rated garage entry door must be self-closing, positive latching. The door should be kept closed in case of fire in the garage.

Thank you very much for reading the post. I do hope you found it informative and useful.

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