Printed from the blog of Lori Greene, AHC/CDC, CCPR, FDAI
Allegion
Email: lori_greene@allegion.com, Blog: www.idighardware.com or www.ihatehardware.com


Apr 20 2009

Fire Door Clearance

Category: Fire Doors,Gasketing & ThresholdsLori @ 9:19 pm Comments (4)
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The 2007 edition of NFPA 80 contains an important change regarding the clearance at the bottom of a fire rated door.  In previous editions of this standard, there was a somewhat confusing table (Table 1-11.4) listing different allowable clearance dimensions depending on the flooring material.  The 2007 edition simplifies this requirement, allowing 3/4″ clearance under the bottom of the door regardless of the flooring.  The only exception is when the bottom of the door is more than 38″ above the floor, ie. dutch doors and counter shutters.

clearance2Unfortunately, there isn’t a definition of “clearance” to make the requirement crystal clear, but according to my research, the 3/4″ dimension is measured between the bottom of the door and the top of the flooring or threshold.  In cases where a fire-rated door has more than 3/4″ between the bottom of the door and the flooring, a threshold can be added to help close that gap.  In most cases the maximum threshold height is 1/2″ due to accessibility requirements.

Here is the text from the 2007 Edition:

4.8.4 Clearance. 4.8.4.1 The clearance under the bottom of a door shall be a maximum of 3⁄4 inch (19 mm). 4.8.4.2 Where the bottom of the door is more than 38 in. (965 mm) above the finished floor, the maximum clearance shall not exceed 3⁄8 in. (9.5 mm) or as specified by the manufacturer’s label service procedure.

4 Responses to “Fire Door Clearance”

  1. M Wolchko says:

    8 Jan 13

    Sometimes a lot easier to add a fire rated door bottom – most mfg of saddles, weather striping, etc, have them, FIRE RATED, in variety of styles & finishes. Avoids having to mess around w/ ADA threshold conditions.

    • Lori says:

      I don’t know of a door bottom that can be used on a fire door where the clearance is greater than what is allowed by NFPA 80, but I’ve been looking for one. I’d appreciate a manufacturer and model number if you have one.

  2. Sheldon says:

    When is the bottom of a door more than 38 inches above the finish floor? Is that a typo, that should read 3/8 inch?

    • Lori says:

      Hi Sheldon –

      It’s not common to have a door with the bottom above 38″ but this would apply to a chute access door or a counter shutter.

      – Lori

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