IBC 2015 R-2 Single Exit with duplex apartments

[bbehin]

Hello Jerry,

I'm writing about an R-2 project in New Jersey, IBC 2015 NJ Edition.

It is a three or four story building (more on that below), less than four units per floor (less than 10 occupants per unit), sprinklered,

I would like to use 1006.3.2 "Single Exits", condition 1 (table 1006.3.2(1)), which allows one exit for R-2 occupancies up to the third floor above grade, as long as the building is sprinklered, there are four or less units per floor, "maximum common path of egress travel distance" is 125 feet, and bedrooms are equipped with emergency escape and rescue openings.

1) If the third floor units are duplexes, with living space at the fourth floor, bedrooms on the third floor only (having emergency escape and rescue openings on the third floor), an internal unenclosed stair in each unit connecting the third and fourth floor areas of the units, and the front door of the duplex units providing access to a single exit stair on the third floor, am I still allowed to have just one exit if the path of travel is kept below 125 feet? I think I've seen something like this built under a previous version of the code, and am wondering if the 2015 code allows it.

2) How do you interpret "common path of egress travel distance" when there's just one exit? Is the 125 feet from the furthest point inside the unit to a rated exit corridor or exit stair? Is it possible to avoid a rated stair if the the travel distance from the furthest point within a unit on the top floor to the main building exit door to the public right-of-way at grade is less than 125 feet?

Thank you
Behrang

[Jerry Peck - Codeman]

[bbehin]

Jerry,

Thank you for the prompt, thorough (and poetic!) response. Sorry for the confusion. Yes,by 'duplex', I meant a two-story dwelling unit. I was hoping that based on 1006.3, which states that "the path of egress travel to an exit shall not pass through more than one adjacent story", we could rely on access to the floor 3 exit from the fourth floor through the third floor, but I understand based on your reading that Table 1006.3.2(1) explicitly forbids occupancy on the fourth floor with access to a single exit when employing condition (1) of 1006.3.2.

We may end up keeping the project only 3 stories tall in order to achieve the single exit, since the building footprint is small enough that adding another exit stair and a corridor means you don't get much bang for the buck with the fourth floor.

Your response is much appreciated - it is very helpful. If you don't mind, please let me know what you think about a related issue on a different project:

I am starting another project with a related issue, where I'm hoping to employ 1006.3.2 condition 5, which allows multistory dwelling units to have access to a single exit from the dwelling unit if that exit access leads to two independent exits outside of the dwelling unit's entrance.

It is a four story R-2 building. Floor 1 is parking. Two exit stairs lead from grade/public right of way to a corridor on floor 2. The building has six three-story apartments, all starting at floor 2 and going up to floor 4. All the three-story apartments have access to two exits via the floor 2 corridor. So, for example, the exit access path for the top level of an apartment (at floor 4) is through an internal unenclosed stair in the apartment connecting floors 4,3, and 2. At floor 2, one can leave the apartment through its entrance door and gain access to two independent exits from the floor 2 corridor. Each apartment has less than 10 occupancy load and 125 feet travel distance (counting the internal stairs) to its entrance, at which the common path of egress travel ends since two exits are available at the two ends of the corridor.

My reading of 1006.3.2.5 is that this is allowed. However, given that 1006.3 states "the path of egress travel to an exit shall not pass through more than one adjacent story", can 1006.3.2.5 be employed for a three-story dwelling unit or does 1006.3 limit the number of stories of a multi-story dwelling unit under 1006.3.2.5?

Also, I assume table 1006.3.2(1) doesn't apply here since it only applies if using condition 1006.3.2.1

Thank you again!
Behrang

[bbehin]

Jerry,

In case the description of the second project in my previous note wasn't clear, here is a simplified diagram illustrating the basic arrangement.

Thank you!

[Jerry Peck - Codeman]

[bbehin]

Jerry,

Thank you for the explanation. Yes, the path will be measured at right angles, and the corridor will be sprinklered, and corridor and stairs will be rated.

Many thanks for your help

Best Regards
Behrang