Door Undercuts

Q: What is the maximum you can have between the bottom of door and the thresholds for a fire-rated door assembly? I have some stairwell doors with 1 inch to 1 ¼ inch gap between the bottom of the door and the threshold.

A: That will be a problem. According to section 8.3.3.1 of the 2012 Life Safety Code, you must install fire-rated door assemblies in accordance with NFPA 80-2010. Section 4.8.4.1 of NFPA 80-2010 says the clearance under the bottom of the door shall be a maximum of ¾ inch. Also, section 7.2.1.15.2 of the 2012 Life Safety Code says you must maintain the fire rated door assemblies in accordance with NFPA 80.

Any clearance under the bottom of the door (while it is in the closed position) that exceeds ¾ inch will be considered non-compliant. There are after-market devices available that you can install on the door to fill that gap, but you must be very careful as you can only install devices that have been listed by an independent testing laboratory (i.e. UL, FM Approval, Intertek) that have been approved for that purpose.

Keep in mind that there are limitations on the door material, amount of clearance, and the rating.  Here are links to information on 3 products suggested to me by Lori Greene (see her website at www.idighardware.com), but there may be more:

Zero:  http://idighardware.com/2013/03/solution-for-oversized-undercuts/

NGP:  http://idighardware.com/2015/01/new-products-for-oversized-fire-door-clearances/

Crown:  http://idighardware.com/2014/06/a-fire-door-test-first-hand/

Brad Keyes
Brad Keyes, CHSP

Brad is a former advisor to Healthcare Facilities Accreditation Program (HFAP) and former Joint Commission LS surveyor. He guides clients through  organizational assessment; management training; ongoing coaching of task groups; and extensive one-on-one coaching of facility leaders. He analyzes and develops leadership effectiveness and efficiency in work processes, focusing on assessing an organization’s preparedness for a survey, evaluating processes in achieving preparedness, and guiding organizations toward compliance. 

As a presenter at national seminars, regional conferences, and audio conferences, Brad teaches the Keyes Life Safety Boot Camp series to various groups and organizations. He is the author or co-author of many HCPro books, including the best-selling  Analyzing the Hospital Life Safety Survey, now in its 3rd edition. Brad has also authored a variety of articles in numerous publications addressing features of life safety and fire protection, as well as white papers and articles on the Building Maintenance Program. Currently serving as the contributing editor of the monthly HCPro newsletter Healthcare Life Safety Compliance  gives Brad further insight into the industry’s trends and best practices.