Common path pf egress travel
Hello All,
I would like to clarify the meaning of this section of IBC:
1. I do not understand how "common path" could be considered for one exit situation if it by definition exists only with 2 or more exits, hence the word "common"? Also, very confusing requirement to consider "common path" to define the number of exits as this path is determined by already known location of those exits.
2. If we disregard the 1st question (above), does this section say that common path is not limited to the length in the table if I provide 2 exits from the space? Than with 2 exits in place the common path could be anything I want?
Also, I have found this document and not sure if it suggests that this wording in code must be corrected:
https://www.iccsafe.org/wp-content/uploads/IBC-2-2-9_5_common-path-of-travel-2017.pdf
Nevertheless, I hope someone can clarify this puzzle, as I'm sure we need to understand this for the test.
Thank you,
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If you read the definition of the common path of egress travel a few more times, you will understand. For your question 1, for example, if a space only need to have one exit, and a person has to travel a distance of 60’ from the furthest point in the space to the exit, once he gets to the exits, he has two ways to escape, like escape towards two different directions of a corridor that lead to two different exits. In this case, the common path of egress travel is 60’. So, for a space requires only one exit, you still have a common path of egress travel.
Gang Chen, Author, Architect, LEED AP BD+C (GreenExamEducation.com)
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If you understand the concept of common path of egress travel, then the answer to your 2nd question is also very straight forward:
Two exist are required when:
- The number of occupants for a space exceeds the occupant load listed in Table 1006.2.1, OR
- The common path of egress travel distance exceeds the number listed Table 1006.2.1
This section of IBC is actually very important.
In real practice, you may need to draw a dashed polyline on your floor plan to show the worst-case scenario of your occupants’ common path of egress. You can measure the total length of the dashed polyline to get the actual travel distance.
Common path of egress is rarely a straight line because you have fixtures or shelving blocking the direct travel path in most cases. So, you probably have to zigzag your polyline.
We have to do this per plan checker’s comments many times in our daily practices.
I’d not be surprised to see some real ARE exam questions on this section.
Gang Chen, Author, Architect, LEED AP BD+C (GreenExamEducation.com)
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Gang,
What I'm getting is that there is a difference between an exit from the space (room) and an exit from a story or building.
In this image below, I marked exits from the space number 1, and exits from the story number 2.
Thus, section 1006.2 says that when two or more exits from the story are required, there can be only one exit from the space (room) if common path of travel and occupant load are under the set limit.
Than I wonder how the number of exits from the story (2) are defined, and I find this:
In other words: One egress stair (as on the plan above) will be enough, if the common path of egress in under the set limit. But this is already the ultimate exit from the story, and if there is only one such exit than the common path of egress equals exit access travel distance. There is no point where two ways out are available since there is only one exit stair. So I'm not sure why this term "common path" is used in context of exit from the story?
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Your statement that “I can have only one egress stair” is not correct, you can have at least one stair. If the owner wants to put in two exits. S/he certainly can. The codes defines minimum number of exits required, not the maximum number of exits allowed.
Common path of travel has been clearly defined by the IBC, everyone should know the meaning. It is convenient to use it.
Gang Chen, Author, Architect, LEED AP BD+C (GreenExamEducation.com)
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Correct, except the red line with arrow should extend all the way to the actual exit on the ground level.
Gang Chen, Author, Architect, LEED AP BD+C (GreenExamEducation.com)
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Hello Artem,
I recommend watching Marty Huie's youtube videos explaining common path of travel. I found his illustrations and explanation most helpful to understand the concept. https://www.youtube.com/watch?v=bJG6ydNMjbs
Furthermore, I would reference Building Codes Illustrated by Ching if you haven't already. It has proved to be a helpful companion to studying code sections. As a visual learner I am able to retain information better from BCI.
Best, Liz
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Based on the link the OP posted from ICC https://www.iccsafe.org/wp-content/uploads/IBC-2-2-9_5_common-path-of-travel-2017.pdf it would appear that there is an inconsistency of verbiage in the code which coincides with the same difficulties I have noticed before as well. Tables 1006.2.1, 1006.3.2(1) and 1006.3.2(2) indicate CPETD but the footnotes refer to exit access travel distance. The previous code versions clearly delineated between Common Path Egress Travel and Exit Access Travel Distance also. Now in 2015 it seems they have been combined. I run into this many times at our office and after much research and also reading the commentary, in a single exit building the common path of egress travel distance really becomes your exit access travel distance. If that is the case (and what I have done professionally) is take the distance from the most remote point to the exit door (for a proposed single exit building) and if that exceeds the CPETD (i.e. your exit access travel distance) then you need a second exit from the building/ space. Even the code commentary to section to 1006.3.2.(2) (pg 10-31) uses the language "exit access travel distance" and not common path of egress travel distance when describing the criteria for allowing a single exit building. Overall, I think we know what IBC is getting at, but the code needs to be cleaned up.
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