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2009 NJ IBC: R-2 bldg with one exit

S

Scott_R

Bronze Member
Joined
Apr 27, 2011
Messages
44
Location
Chicago, IL
2009 IBC - New Jersey Edition

Type VB

Three Stories

R-2 Use w/ S-2 private garages on one side of bldg. at grade

No basement

Fully sprinklered

10 units per building/fire area (2 + 4 + 4)

Ground floor: 2 units one side of bldg, 6 individual private garages on other side. 2 means of egress provided from corridor to exterior.

2nd and 3rd floors: 4 units/floor. Units exit to corridor and to one exit stair as per sections 1021, 1022 and table 1021.2

Questions:

1. Does the exit stair on floors 2,3 need to be an exit enclosure or can the stair be open?

2. If a fire barrier (2 hour) is provided, can modules of 10 units be attached to create a 20 and 30 unit building? Each fire area will have 4 units/story per exit.

Thank you,

Scott
 
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Scott, the travel distance for all the second and third floor dwelling units complies with the 50 ft. max. of Table 1021.2?
 
Yes, travel distance is met, no dead end corridors, etc. Just to be clear, it is a "pod" concept. 4 units with one stair per floor/pod - the pod is "mirrored" so each pod has one exit stair. There is a 10 unit module (one stair), a 20 unit and a 30 unit (all repeated - never more than 4 units per stair per fire area - each module has a stair so a 20 unit would have 2, a 30 unit would have 3).
 
Your pod concept could also be limited by allowable area...I don't have 2009 NJ IBC. 2006 IBC has an allowable tabular area of 7,000 sq. ft. per story for R-2. In order to use the sprinkler area increase you would need an NFPA 13 sprinkler system. You could use fire walls to separate pods into buildings that meet the allowable area; fire barriers do not create separate buildings. Don't know NJ amendments or the 2009 IBC unamended.
 
TJacobs said:
Your pod concept could also be limited by allowable area...I don't have 2009 NJ IBC. 2006 IBC has an allowable tabular area of 7,000 sq. ft. per story for R-2. In order to use the sprinkler area increase you would need an NFPA 13 sprinkler system. You could use fire walls to separate pods into buildings that meet the allowable area; fire barriers do not create separate buildings. Don't know NJ amendments or the 2009 IBC unamended.
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Thanks. The building will have sprinklers as required for 3 stories R2 and the area does not exceed 7,000 per floor. I read the table 1021.2 as one exit "per floor". I know fire barriers do not create separate buildings, so I need to clarify this concept works as intended per table 1021.2?
 
Per your original question #1

Does the exit stair on floors 2,3 need to be an exit enclosure or can the stair be open?
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, what code section are you using to exempt them? Per the 2009 Commentary of that section I don't see where they are exempt. The commentary states that the stairways must be within the dwelling or sleeping units. It sounds like you're describing common stairs? Even if that stair was permitted to be open, I’m still doubtful that an occupant could get from the most remote point of a 2nd or 3rd story unit, out their front door, over to the stairs, down the stairs (path of travel measured per 1016.1) to an exit discharge within 50 ft. to comply with Table 1021.2*. Without seeing the floor plans, I think you need two enclosed stairways from each floor. If for some reason you can comply with the single exit allowed by Table 1021.2, I don’t see where a fire barrier of any rating will allow you to increase the number of dwelling units (original question #2) but I have a call in to the code assistance unit at DCA.

* You may get an increase to 75 ft. from the 3rd floor if there are emergency escape and rescue windows as well as the sprinklers.
 
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Scott_R said:
2009 IBC - New Jersey Edition Type VB Three Stories R-2 Use w/ S-2 private garages on one side of bldg. at grade No basement Fully sprinklered 10 units per building/fire area (2 + 4 + 4) Ground floor: 2 units one side of bldg, 6 individual private garages on other side. 2 means of egress provided from corridor to exterior. 2nd and 3rd floors: 4 units/floor. Units exit to corridor and to one exit stair as per sections 1021, 1022 and table 1021.2 Questions: 1. Does the exit stair on floors 2,3 need to be an exit enclosure or can the stair be open? 2. If a fire barrier (2 hour) is provided, can modules of 10 units be attached to create a 20 and 30 unit building? Each fire area will have 4 units/story per exit. Thank you, Scott
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A diagram would be helpful.
 
DCA has confirmed that, baring firewall separation into separate buildings, additional fire barriers won't permit additional dwelling units beyond 4 and still comply with a single exit from that story. Also, please disregard my earlier comment about a possible increase to the 3rd floor travel distance. I was mislead by the commentary.
 
1

. 2009 IBC - New Jersey EditionType VB

Three Stories

R-2 Use w/ S-2 private garages on one side of bldg. at grade

No basement

Fully sprinklered

10 units per building/fire area (2 + 4 + 4)

Ground floor: 2 units one side of bldg, 6 individual private garages on other side. 2 means of egress provided from corridor to exterior.

2nd and 3rd floors: 4 units/floor. Units exit to corridor and to one exit stair as per sections 1021, 1022 and table 1021.2

Questions:

1. Does the exit stair on floors 2,3 need to be an exit enclosure or can the stair be open?

2. If a fire barrier (2 hour) is provided, can modules of 10 units be attached to create a 20 and 30 unit building? Each fire area will have 4 units/story per exit.

Thank you,

Scott,
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It looks like the plan you attached is a pair of typical 2nd or 3rd floor plans of what you described above with a 2 hour area separation wall between the two halves. Is this ASW (with the two 1” gypsum liner panels?) intended to serve as a fire wall? If so, I think that will allow you to stay below the maximum number of dwelling units per floor.

However, I have strong doubts that the exits work.

1021.1

Requires 2 exits with your presumed occupant load (Table 1021.1).

Even if you have a compliant 2 hour fire wall breaking the footprint into separate buildings to keep the number of dwelling units to a max. of four per story, I just can’t see how you comply with the 50 ft. travel distance requirements of Table 1021.2 under exception No. 2. The dwelling unit entry doors are not the exit.
 
Something that I forgot to suggest is that perhaps you could rate the walls between the dwelling units and the common space where the stair is located as the one-hour exit enclosure per 1022.1 (I don’t think you comply with exception 1). This would essentially make the dwelling unit doors the exits. If all the occupants can reach those doors within the 50 ft travel distance I think you can get by with the single stair.
 
Yes, walls between units are fire partitions. Wall between 4 unit pod is area separation wall (separate buildings). Doors from units to stairs are less than 50 feet. So this meets the one exit requirement correct?

What about openness of stair between floors? If the common area is the fire exit, would this be allowable?
 
Yes, walls between units are fire partitions. Wall between 4 unit pod is area separation wall (separate buildings). Doors from units to stairs are less than 50 feet. So this meets the one exit requirement correct?What about openness of stair between floors? If the common area is the fire exit, would this be allowable?
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Scott,No, I don’t think you meet the 50 ft travel distance requirement to use Table 1021.2. Take a look at 1016.1. The travel distance isn’t measured from the unit entry doors to the top of the stairs (if I’ve understood the meaning of your third sentence above.) It’s measured from the most remote point within any of the dwelling units on that story “along the natural and unobstructed path of egress travel to an exterior exit door at the level of exit discharge, an entrance to a vertical exit enclosure, an exit passageway, a horizontal exit, an exterior exit stairway or an exterior exit ramp…” The path along unenclosed stairs is also included (see last paragraph of 1016.1). From what I tell by your plan, your exit won’t be reached until what I presume is a common door at the ground floor level which I have to think will far exceed the 50 ft. limit.

What I was trying to suggest before was the possibility of using the walls between the units and the common area where the stair is located as the vertical exit enclosure. You would need fire barriers, not fire partitions for that but still only one-hour although the door ratings would also have to be one-hour. If all occupants on that floor can reach their “front” door from the furthest point within their individual units within 50 ft, it’s my opinion that you may be able to get away with the single stair.

Let me also draw your attention to footnote c of Table 1021.2. Per DCA comment, this means that emergency escape and rescue windows are also required in addition to the fire suppression.
 
Perhaps you already have the number but if not, you could call the code assistance unit within the NJDCA at 609-984-7607. Frequently, you need to leave your name/# but someone will call you back ASAP.
 
Thanks, I have 50' from most remote point in corner bedroom...

So, assuming that is less than 50', building is separated into 2 bldgs. via an area separation wall able to collapse and leave on side standing, does this meet the building with one exit at 4 units per floor criteria?
 
To answer your second question first, my opinion is that yes, by creating separate buildings via the area separation walls (which as far as I know can be used as fire walls), you can create separate buildings of 4 dwelling units per floor. However, (and I'm sorry if I'm beating a dead horse) when you say you have 50' from the most remote point, where are you measuring to? You must be within 50' to an exit. The dwelling unit door is not the exit. The top of the stairs is not the exit. To reach an exit, a third floor occupant has to walk from the remote point within their unit, go through their dwelling unit entry door, walk over to the stairs, walk down that flight of stairs to the second floor, walk around to the next flight of stairs, walk down those and walk to the common front door at the ground floor level that everyone else has to enter and leave by. That point is (most likely) the exit and I just can't believe someone can make it there within 50'.
 
Scott_R said:
Typical floor plate, note area separation wall every 4 units:View attachment 1125
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I am in agreement with Pmarx...it appears you are around 35-40' of travel distance just to reach the egress door for your corner units (remote point @ balcony). The walls shown in your diagram do not indicate a 2-hr enclosure around the stairs (i.e. plumbing in these walls). Without the stair/common area being separated by a fire wall, you will exceed your maximum travel distances trying to reach the front door, even on the first level (depth of front units appears to be 30+ feet).

Rating the walls between the "4-unit pods" and the "stairwell/common area" appear to be requirements for a one exit design as you have shown.
 
Thank you Papio and pmarx.

So, if i read this correctly - I can enclose the stairwell with firewall and provide a fire door and meet the 50' distance when the stair is an enclosed exit enclosure, correct?
 
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