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Reference source for measuring common path of egress travel...

I do not know about CA but he should have no authority about CEPT in the design of a new building. He is not the building official and is not the AHJ who determines if the CPET is code compliant or not.

2018 IFC
[A] 102.4 Application of building code.
The design and construction of new structures shall comply with the International Building Code, and any alterations, additions, changes in use or changes in structures required by this code, which are within the scope of the International Building Code, shall be made in accordance therewith.
 
The project is at a major CA university and SFM is involved. I am pretty certain our interpretation of where to measure to is correct. I just need to convince him.
 
Hopefully someone can clarify this common path measurement issue to me. Think of a fire sprinkled multi tenant high rise building floor plate with a 1 hour rated common corridor that connects the two rated stairs. The suite is large enough to require two exits. My confusion/concern has to do with the termination of the measurement for "Common Path". We have typically measured this to the suite exit doors that enter the 1 hour rated corridor. A Fire Marshal has just given us a correction that the common path measurement needs to continue to the stairwell door. We have a 100' max common path per code. We cannot both paths to the exit stair door within 100'.

Is that the correct way to measure common path, and do both paths to the exits need to fully from CFC 202:

The definition of "Common Path Of Egress Travel in CFC 202"
1655485503905.png

It sounds to me like once you are in the corridor, and you can choose to go left to stair A or right to stair B, you have reached the termination of the common path of egress travel.

1655485364668.png


Regarding previous posts on whether loose furniture constitutes an obstruction, I found this old reference in the 1997 Handbook to the Uniform Building Code published by the then-ICBO, stating that exit travel measurement distance already factored in the potential presence of "tables, chairs, furnishings, cabinets, and similar temporary or moveable fixtures or equipment, allowing a straight line of travel over them. In other words, "unobstructed" already assumed that furniture could get in the way, and "travel around temporary or moveable fixtures need not be considered".

1655486635093.png

Here's the entire page for context:


1655486675864.png
 
The definition of "Common Path Of Egress Travel in CFC 202"
View attachment 9069

It sounds to me like once you are in the corridor, and you can choose to go left to stair A or right to stair B, you have reached the termination of the common path of egress travel.

View attachment 9068


Regarding previous posts on whether loose furniture constitutes an obstruction, I found this old reference in the 1997 Handbook to the Uniform Building Code published by the then-ICBO, stating that exit travel measurement distance already factored in the potential presence of "tables, chairs, furnishings, cabinets, and similar temporary or moveable fixtures or equipment, allowing a straight line of travel over them. In other words, "unobstructed" already assumed that furniture could get in the way, and "travel around temporary or moveable fixtures need not be considered".

View attachment 9071

Here's the entire page for context:


View attachment 9072
Interesting. Exact opposite of what is being put forth today. This from the 2018 Building Code Essentials:
1655487502486.png
 
The suite doors into a corridor don’t cause an end to the common path if you are in a dead end.
 
Sifu, it's quite possible that in the time period between the 1997 UBC and the 2018 IBC, the philosophy of measurement of egress travel changed. I'd like to think there exists a document somewhere that explains when, how and why this changed.
 
Sifu, it's quite possible that in the time period between the 1997 UBC and the 2018 IBC, the philosophy of measurement of egress travel changed. I'd like to think there exists a document somewhere that explains when, how and why this changed.
I had the same thought. Sometimes code is snatched out of thin air, or simply what a committee can agree on. I too would like to think there was some critical thinking here. In most situations I have a hard time seeing a major difference, but as is sometimes the case, somebody could really push the limits and create an excessive path around the "furniture" or any other obstruction that is not the bounding walls, that created a need to provide more definitive guidance.....or maybe they just didn't read the original intent and inserted their own. The language "natural and unobstructed path" found in the various commentaries is subjective. I apply my best judgement to it. But it is good to know that there was an official "unofficial" explanation for it pre-ICC. Anyway, this is all off the original topic, and I think most agree the FM may not be using the correct application of CPET, unless, as Jay Smith points out, there are things we don't know about the situation. Tim may have better aim in reserving judgement without a plan to evaluate.
 
Common Path of Travel did not exist in the UBC Legacy Code and you will not find a reference to it in the Existing Building Code.

The SBCCI classes that I remember taking taught us to measure the exit access travel distance at right angles which is consistent with todays method
 
As best as I remember BOCA also used to measure parallel to the walls. When the 3 model codes combined it was probably 2 against 1. NFPA 101 also appears to measure parallel to the walls (fig. A7.5.1.2.1).
 
Sometimes code is snatched out of thin air, or simply what a committee can agree on.
Years ago someone on this forum (who had worked on many code development committees) commented along these lines: if a prescriptive requirement ends in a 0 or 5 (example: occupant load greater than 50 means doors must swing in direction of exit, or maximum CPET is 100'), chances are it was arrived at arbitrarily, just prior to the committee's lunch break.
 
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