Exit discharge through open, but covered, parking lot

[archclem]

We are designing a 4 story multi-family project with 2 interior exit stairways in 2 hour rated shafts. One of the stairways "discharges" into a covered parking lot which is open on three sides. The lot in this case is covered by the building. It is separated from the building by a 2 hour rated wall on the fourth side and 2 hour rated floor assembly above the lot. The lot is at grade. Can the occupants access the public way through this parking lot?

 

[cda]

Welcome

Which building code and edition??

 

[cda]

We are designing a 4 story multi-family project with 2 interior exit stairways in 2 hour rated shafts. One of the stairways "discharges" into a covered parking lot which is open on three sides. The lot in this case is covered by the building. It is separated from the building by a 2 hour rated wall on the fourth side and 2 hour rated floor assembly above the lot. The lot is at grade. Can the occupants access the public way through this parking lot?

Hum

My first thought is you are in a two rated enclosure. You are supposed to maintain that rating till you get out.
But once you go through the two hour wall,you are in another building


If you are in the lot where is the code compliant exit?

 

[archclem]

2012 IBC

Yes, the stairway is a 2 hour rated enclosure and the parking lot is separated from the building by 2 hour assemblies. Are you suggesting that the parking lot is another building? It doesn't meet the definitions for either habitable or occupiable spaces.

 

[steveray]

Yes.....but the details may be of some debate....

 

[cda]

2012 IBC

Yes, the stairway is a 2 hour rated enclosure and the parking lot is separated from the building by 2 hour assemblies. Are you suggesting that the parking lot is another building? It doesn't meet the definitions for either habitable or occupiable spaces.

Yes technically you have two buildings.

Plus, what I was trying to say normally once you are in a rated enclosure, that rated enclosure is supposed to continue till outside the building.

Not dump into an area with less than the enclosure rating, such as a lobby or parking garage

 

[archclem]

Okay, that is sensible. Do you have specific references in the codes?

 

[cda]

Yep

Which building code and edition??

 

[archclem]

I assume you are referencing 1003.6 Means of egress continuity

 

[cda]

Found corridor continuity
1020.6 IBC 2015

Plus

1028.5

 

[cda]

[A] PUBLIC WAY. A street, alley or other parcel of land open to the outside air leading to a street, that has been deeded, dedicated or otherwise permanently appropriated to the public for public use and which has a clear width and height of not less than 10 feet (3048 mm).

 

[cda]

1003.6 kind of says it also


There are also requirements for garage exiting use itself, will have to find that.

Plus other people will chime in today

 

[cda]

1003.6 kind of says it also


There are also requirements for garage exiting use itself, will have to find that.

Plus other people will chime in

 

[RLGA]

When you leave an exit, you're technically in the portion of the means of egress called the "exit discharge," which you've correctly called it; thus, we should look in Section 1027 for direction and guidance. Exception 1 of Section 1027.1 states that 50% (one exit in your case) is permitted to egress through areas on the level of exit discharge if the three conditions listed are met: (1) The path from exit enclosure to exterior exit door is readily visible and identifiable, (2) the entire area is separated from areas below by a fire-resistance rating equal to the enclosure, and (3) the path from the exit enclosure to the exterior is protected by a sprinkler system.

For condition 1, the entire area is open, so the path to the exit should be visible and identifiable upon exiting the enclosure. For condition 2, if the parking is at grade, then this is a moot issue. For condition 3, since this is a residential building, it is required to be sprinklered, so this should be covered.

 

[cda]

Thank you RGLA

How about since it is not at a public way yet??

And he does not say if the garage is sprinkled

 

[RLGA]

Thank you RGLA

How about since it is not at a public way yet??

And he does not say if the garage is sprinkled

Rarely does a building open directly onto a public way. The exit discharge is still from the exit enclosure, beyond the perimeter of the building to the public way. A path must be provided of width complying with Chapter 10; thus, the occupants should not be required to filter through the parked cars to get out beyond the building.

Since the building contains a Group R fire area, the building must be sprinklered throughout per Section 903.2.8, which includes the associated parking area that is covered by the building.

 

[cda]

RGLA
One last one

The two hour enclosure rating does not have to be maintained all the way

Or does the two hour building wall negate that ?

 

[RLGA]

The stairway enclosure is required to be 2-hour fire barriers, but the rest of the building is not, unless if there was enclosed space below the level of exit discharge. If there were enclosed space below, then a 2-hour horizontal assembly is required between the level of exit discharge and the enclosed space underneath.

 

[ADAguy]

Excellent clarifications of an often confusing issue, thanks RLGA

 

[Yikes]

In addition to the analysis by RLGA, there is another way to think about it. "A covered parking lot which is open on three sides" = an S-2 open parking garage

Restate the question like this: "Can a means of egress for an apartment building discharge into a parking garage?" Now I'm picturing residents exiting from their dwelling units, through a corridor, down a 2-hour stairwell, and into a garage where multiple cars are on fire, and intuitively I'm getting nervous.

That said, it is possible that with just one stairway is going into the garage, it might qualify as a type of "horizontal exit" per 1026. You would need an area of refuge equivalent to the total occupants served by the staircase, but that's probably achievable within the drive aisles of the garage.

The part that makes me nervous is a bunch of people rushing down this stair, they get to the ground level door, sense the fire on the other side, and now they have to go back upstairs (against all the other people pushing behind them) to find the other exits.

 

[RLGA]

Now picture this, occupants exiting their spaces, through a corridor, down a 2-hour stairwell, and into a lobby that is on fire -- similar scenario; however, this same egress condition exists in many residential and office buildings.

Parking structures have an inherently good track record regarding fire events (i.e., they catch fire very rarely). Since a lobby is enclosed, smoke can be trapped within the space. On the other hand, in an open parking garage (assuming the openings meet the required areas) the accumulation of smoke will likely be less of an issue than within an enclosed lobby.

 

[ADAguy]

Ouch, serious concerns and possibilities but shouldn't fire sprinklers control the fire in a garage, unless an EQ has disabled them.

 

[Francis Vineyard]

406.5 Open parking garages. Studies and tests of fires in open parking garages have shown that, in addition to a low fire loading, the potential for a large fire is exceedingly remote. Based on this data, the IBC establishes special provisions for open parking garages in this section, which in general are less restrictive than those for enclosed parking structures addressed in Section 406.6. The key is that the open parking garage is well ventilated naturally, and as a result, the products of combustion dissipate rapidly and do not contribute to the spread of fire.

1028.3 Exit discharge components. The general concept of the exit discharge portion of the means of egress is that the components be sufficiently open to the exterior to prevent the accumulation of smoke and toxic gases. As occupants reach the exterior of the building at grade level, they expect to have arrived at a point of relative safety. Where adequate natural cross ventilation is available to disperse any smoke or gases that may be present, one of the major fire- and life-safety concerns is assumed to have been addressed. It is common that roofed areas be provided at the exterior side of exterior exit doors in order to provide weather protection and/or decoration. Such areas are typically considered as a portion of the exit discharge where they are adequately open on the sides to provide for adequate natural ventilation.

Source 2015 IBC Handbook

 

[cda]

In addition to the analysis by RLGA, there is another way to think about it. "A covered parking lot which is open on three sides" = an S-2 open parking garage

Restate the question like this: "Can a means of egress for an apartment building discharge into a parking garage?" Now I'm picturing residents exiting from their dwelling units, through a corridor, down a 2-hour stairwell, and into a garage where multiple cars are on fire, and intuitively I'm getting nervous.

That said, it is possible that with just one stairway is going into the garage, it might qualify as a type of "horizontal exit" per 1026. You would need an area of refuge equivalent to the total occupants served by the staircase, but that's probably achievable within the drive aisles of the garage.

The part that makes me nervous is a bunch of people rushing down this stair, they get to the ground level door, sense the fire on the other side, and now they have to go back upstairs (against all the other people pushing behind them) to find the other exits.

Without seeing plans makes it harder

I thought there was a recent thread on slope and other requirements, if a garage was used as exiting???