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Dec 31 2014

Decoded: Calculating the Egress Width of Door Openings (February 2015)

Category: DHI,Doors & Frames,EgressLori @ 7:18 am Comments (3)
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This post was published in the February 2015 issue of Doors & Hardware

[Click here to download the reprint of this article.]

This pair of doors has been changed to a single door with a fixed panel.  The AHJ must be consulted before a modification like this is begun.

This pair of doors has been changed to a single door with a fixed panel. The AHJ must be consulted before a modification like this is begun.

A common question when replacing doors and hardware during a renovation is whether one leaf of a pair can be “fixed” in place, or whether an opening can be eliminated completely. It’s very risky to make this decision without consulting the Authority Having Jurisdiction (AHJ), but it is helpful to understand some of the factors that could affect the location, size, and quantity of required exits before preparing your request for the AHJ.

Generally, the International Building Code (IBC) requires each space to have at least two exits or exit access doorways, and Chapter 10 states, “It shall be unlawful to alter a building or structure in a manner that will reduce the number of exits or the capacity of the means of egress to less than required by this code.”  But the required number of exits / exit access doorways may be increased or decreased depending on several factors:

  • For rooms or spaces with a low occupant load, one exit may be acceptable. For example, Table 1015.1 in the 2012 edition of the IBC allows a single exit for Assembly, Business, Educational, Factory and Industrial, Mercantile, and Utility occupancies with an occupant load of 49 or less.
  • For larger spaces in these use groups with an occupant load of more than 49, a second exit would be required.
  • For spaces with a high occupant load, the IBC requires additional exits – a minimum of 3 exits for any space with an occupant load of 501 to 1,000, and 4 exits if the occupant load is more than 1,000.
  • Consult the code for information specific to your project, as there are several exceptions to these requirements.

Section 1005 of the 2012 IBC covers Means of Egress Sizing, including sizing for stairways and “other egress components” – doors, gates, corridors, aisles, and ramps. The required egress width for these “other” components of an egress route is calculated by multiplying the occupant load served, by the egress capacity factor:

  • For buildings without a sprinkler system and emergency voice/alarm communication system – the egress capacity factor is 0.2 inches per occupant.
  • For H (High Hazard) and I-2 (Institutional – typically hospitals and nursing homes; refer to the code for the full definition) – the egress capacity factor for doors is 0.2 inches per occupant.
  • For other use groups (H and I-2 excluded) with a sprinkler system and emergency voice/alarm communication system – the egress capacity factor for doors is 0.15 inches per occupant.

For example, if the occupant load of a nonsprinklered space is 300 occupants, the required egress width of the exits or exit access doorways serving that space is 300 occupants x 0.2 inches per occupant = 60 inches. So the egress doors serving that space must have a total of 60 inches of clear width.  This doesn’t mean that an equal pair of doors providing 30 inches of clear width each is sufficient, because of the requirements for multiple exit locations and minimum clear width (read on).

NFPA 101To determine the egress capacity of a door, or how many people a door will accommodate, divide the clear opening width of the door by 0.2 inches per occupant or 0.15 inches per occupant (see above to choose which factor to use). For example, if a door in a nonsprinklered building has a clear opening width of 32 inches, the egress capacity of that door would be 32 inches / 0.2 inches per occupant = 160 occupants.

The clear opening width of a door is measured from the face of the door with the door open 90 degrees, to the stop on the strike jamb of the frame. For pairs of doors, the clear width of the active leaf is measured from the face of the door to the removable mullion or to the edge of the inactive leaf in the closed position. To calculate the egress width of the entire opening for a pair without a mullion, measure between the faces of both doors when open to 90 degrees.

If you’re looking at a door on a set of plans rather than measuring the clear width of an existing door, the exact clear opening width can vary slightly depending on the hinges or pivots. But a rule of thumb to find the nominal clear opening width for a single door hung on full mortise hinges is to take the frame opening width and subtract half of the hinge width, the hinge backset, and the height of the stop on the strike jamb. So for a 3-foot door that is hung on 4 1/2-inch-wide hinges with a ¼-inch hinge backset and a 5/8-inch stop, the calculation would be 36 inches (frame opening width) – (2 ¼ inches (half of the hinge width) + ¼ inch (hinge backset) + 5/8 inch (frame stop)) for a total of 32 7/8 inches of clear width.

Remember, doors in a path of egress and doors on an accessible route are typically required to have a clear opening width of at least 32 inches. In some cases this required width is increased for doors in health care facilities, or may be decreased for some existing doors. For pairs of doors, at least one leaf is required to provide the 32-inch clear width unless the applicable code or standard contains an exception that would allow an alternative.  The IBC also includes a limit on the maximum width of egress doors – doors in a means of egress may not be more than 48 inches wide.*

There are additional factors that may affect the size and location of egress doors, such as limitations on travel distance and the common path of travel, as well as the requirement for exits to be remotely located from each other. These requirements will be covered in the next edition of Decoded.

Photo: Logan Piburn, Dyron Murphy Architects.

* NFPA 101 no longer limits the maximum width of egress doors – past editions limited the width to 48 inches.  A proposal has been submitted to remove the 48-inch limitation from the 2018 IBC, but it has not yet been approved.

3 Responses to “Decoded: Calculating the Egress Width of Door Openings (February 2015)”

  1. Cda says:

    Very good

    Also watch maximum door width

  2. Pat Mares says:

    “For example, if the occupant load of a nonsprinklered space is 300 occupants, the required egress width of the exits or exit access doorways serving that space is 300 occupants x 0.2 inches per occupant = 60 inches. So the egress doors serving that space must have a total of 60 inches of clear width. This doesn’t mean that a pair of 30-inch wide doors is sufficient, because of the requirements for multiple exit locations and minimum clear width (read on).”

    I’m a little confused. Does a 30-inch wide pair of doors have a clear width of 60 inches? Seems like it would be 58 3/4″ with swing clear hinges and 5/8″ stops on frame. Or, am I not understanding correctly?

    P.S. – I’m really learning a lot on your “Decoded” webinar.

    Thanks.

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