Common path of egress travel and path convergence in R3 single family

[sylvan]

We are working on a change of use in San Francisco, converting a single story type III private car garage (U) to a three story + roof deck type V single family residence (R3). This project falls under the 2013 California Building Code (uses the IBC model code). The problem we're facing at the moment is the exit travel distance from the roof deck. The building will be fully sprinklered with a type 13-R system, extending our allowable common path travel distance to 125 ft. However, we've got 150 ft from the back corner of the roof deck to the front door. The allowable exit access travel distance is 250 ft, but we're only working with a single exit, so the common path of travel dictates our travel distance.

Here's the question: if we provide two exit access stairs from the roof deck down to the 3rd floor, and then proceed with one exit access stair from 3rd to 2nd and 2nd to ground, does this mean our CPOET limit starts when we reach the 3rd floor? Have we effectively removed the CPOT from the roof deck by providing two exit access stairs down to the 3rd floor?

The definition for CPOET is as follows:

COMMON PATH OF EGRESS TRAVEL. That portion of exit access which the occupants are required to traverse before two separate and distinct paths of egress travel to two exits are available. Paths that merge are common paths of travel. Common paths of egress travel shall be included within the permitted travel distance.

The part about "paths that merge..." is the part that seems to be a "no" answer to my question. The reason I still think this is a valid question is that the path of travel isn't merging on the same floor, it doesn't merge until you reach the top of the stairs on the 3rd floor.

Thanks in advance for your time and help. I look forward to hearing everyone's thoughts.

 

[cda]

Welcome.....

 

[cda]

Best I can give you,,,

The common path of egress travel is a concept used to refine travel distance criteria. A common path of travel is the route an occupant will travel where the only way in is also the only way out, similar to a dead-end corridor. The length of a common path of egress travel is limited so that the means of egress path of travel provides a choice before the occupant has traveled an excessive distance (see Section 1014.3). This reduces the possibility that, although the exits are remote from one another, a single fire condition will render both paths unavailable.

 

[sylvan]

...a single fire condition will render both paths unavailable.

Thanks, CDA, for the response. I think I understand the purpose of the CPOET limits. To your point about a single fire condition - if the fire is on the roof then by providing two stairs we've effectively provided a sure way out without running through the fire . If you're on roof and the fire is on the 3rd floor, the two ways off the roof will also provide some flexibility in getting around the fire. In fact, the two stairs off the roof would even improve the condition for anyone on the 3rd floor during a fire on the same level by allowing them to run up over the roof and down the other side if necessary. It seems to me that by providing two exit access stairs off the roof we've not only made it as safe as a three story (no roof deck) building, we've made it safer by providing two easy ways to escape from the 3rd floor to a location that can easily be accessed by a ladder truck.

All that said, I'm not clear on whether the code sees it the same way. This may have to be decided by the local authority as an equivalency.

 

[mtlogcabin]

CPOT is not applicable under the IBC for an R-3 use. Compare this IBC section against your CA codes and see if it helps

And WELCOME to the board

1021.2 Exits from stories.

Two exits, or exit access stairways or ramps providing access to exits, from any story or occupied roof shall be provided where one of the following conditions exists:

1. The occupant load or number of dwelling units exceeds one of the values in Table 1021.2(1) or 1021.2(2).

2. The exit access travel distance exceeds that specified in Table 1021.2(1) or 1021.2(2) as determined in accordance with the provisions of Section 1016.1.

3. Helistop landing areas located on buildings or structures shall be provided with two exits, or exit access stairways or ramps providing access to exits.

Exceptions:

1. Rooms, areas and spaces complying with Section 1015.1 with exits that discharge directly to the exterior at the level of exit discharge, are permitted to have one exit.

2. Group R-3 occupancy buildings shall be permitted to have one exit.

 

[sylvan]

2. The exit access travel distance exceeds that specified in Table 1021.2(1) or 1021.2(2) as determined in accordance with the provisions of Section 1016.1.

Ok, table 1021.2(1) is also what I was looking at when I was thinking that two exits from the roof is an acceptable condition when exceeding the 125 ft travel distance limit. Here in SF the plan checkers often consider the CPOET as the limiting condition since it matches the values in 1021.2(1) for R3.

I just re-read section 1021.1 and I think it clinches the answer as a sold NO to my original question. We cannot reduce the number of access stairs:

1021.1 General. Each story and occupied roof shall have the

minimum number of independent exits, or access to exits, as

specified in Table 1021.1. A single exit or access to a single

exit shall be permitted in accordance with Section 1021.2.

The required number of exits, or exit access stairways or

ramps providing access to exits, from any story shall be maintained

until arrival at grade or a public way.

 

[mtlogcabin]

Ok, table 1021.2(1) is also what I was looking at when I was thinking that two exits from the roof is an acceptable condition when exceeding the 125 ft travel distance limit. Here in SF the plan checkers often consider the CPOET as the limiting condition since it matches the values in 1021.2(1) for R3. I just re-read section 1021.1 and I think it clinches the answer as a sold NO to my original question. We cannot reduce the number of access stairs:

1021.1 General. Each story and occupied roof shall have the

minimum number of independent exits, or access to exits, as

specified in Table 1021.1. A single exit or access to a single

exit in accord shall be permitted in accordance with Section 1021.2.

The required number of exits, or exit access stairways or

ramps providing access to exits, from any story shall be maintained

until arrival at grade or a public way.

Re-read what you posted and that I highlighted in blue. then read exception #2

R-3 is not included in Table 1021.2(1) or (2). The travel distance in both tables is the MAXIMUM exit access travel distance allowed for a single exit in the occupancy groups listed.

 

[steveray]

I think MT is giving you great advice...Just make sure the Cali Code matches....

 

[sylvan]

Thanks everyone for your input. The 2013 CBC strays a little from the IBC in that table 1021.2(1) does include R-3 occupancy. As best I can tell, the 2012 IBC unequivocally allows one exit from an R-3 occupancy (2012 IBC 1021.2 Exception 2). The 2012 IBC also limits the exit access travel distance to the values in table 1016.2 (200ft or 250 ft w/ sprinkler). The 2013 CBC is more restrictive, and includes R-3 occupancy in table 1021.2(1), thereby allowing one exit only when exit access travel distance is 125 ft max. AND an NFPA 13 or 13R (but not 13D) sprinkler system is provided.

Furthermore, both the 2012 IBC and the 2013 CBC require that the number of exit access stairways be maintained until arrival at grade (1021.1).

To summarize, it is my understanding the IBC and CBC have different limits as follows:

2012 IBC allows a single exit from R-3 occupancy with up to 250ft (sprinklered) travel distance, unless it is part of a mixed occupancy structure, in which case CPOET limits apply (table 1014.3).

2013 CBC allows a single exit from R-3 occupancy with up to 125 ft (sprinklered) travel distance. The CPOET for mixed occupancy has the same limit (table 1014.3).

Does anyone think I've missed the mark here?