This question is a good one for anyone responsible for maintaining or inspecting fire doors:

If NFPA 80 requires 1/8-inch or 3/16-inch maximum perimeter clearance for fire door assemblies, is it acceptable to add the manufacturing tolerance to that dimension?

Here’s a refresher on clearances:

  • For swinging hollow metal doors, NFPA 80 requires the clearance at the top and vertical edges and the meeting stiles of pairs to measure 1/8-inch, +/- 1/16-inch.
  • Starting with the 2016 edition of NFPA 80, 20-minute-rated wood doors and high-pressure decorative laminate (HPDL) doors in hollow metal frames are allowed to have the same clearances as hollow metal doors – 1/8-inch, +/- 1/16-inch.  Previous editions of the standard require 20-minute wood doors to have a maximum clearance of 1/8-inch at the head, jambs, and meeting stiles of pairs.  (Check to see which edition is referenced by the adopted code in the project’s jurisdiction.)
  • Wood doors and HPDL-faced doors of a higher rating, and doors of other materials that are not mentioned above, shall not have clearances greater than 1/8-inch at the head, jambs, and meeting stiles.

What about manufacturing tolerances?  For example, there is a standard from the Steel Door Institute – SDI-117, which permits manufacturing tolerances of up to 1/16-inch on hollow metal frames.  Is that tolerance added to the clearance allowed by NFPA 80?

I checked Annex A of NFPA 80, which includes explanatory information to help clarify the intent of NFPA 80, and I found this paragraph:

A. The clearance dimension between the door(s) and the door frame affects the assembly’s ability to form a suitable barrier under fire conditions. NFPA 252, UL 10B, Standard for Safety Fire Tests of Door Assemblies, and UL 10C, Standard for Positive Pressure Fire Tests of Door Assemblies, specify the clearance dimensions between the doors and frames and the meeting stiles of paired doors to be no greater than 1∕8 in. (3.18 mm) for door assemblies subjected to fire tests conducted by one of the nationally recognized testing laboratories, regardless of the door or frame material; no over-tolerance for the clearance dimension is permitted. When the clearance gaps along the vertical and top edges of doors and between meeting stiles of paired doors exceed the prescribed dimensions, the assembly’s ability to perform like the test unit is reduced and the assembly should not be expected to provide the same level of protection.

I wanted to be absolutely sure so I submitted the question to NFPA staff, and they clarified that the limits established by NFPA 80 apply to the installed condition, and it is not the intent of NFPA 80 to permit manufacturing tolerances in addition to the clearances listed in the standard.

Any questions?

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