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Exterior Exit Stair closer than 10' to a lot line?

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nealderidder

Sawhorse
Joined
Dec 7, 2010
Messages
394
Location
Sacramento, CA
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I'm pondering an exterior exit stair for a 4 story mixed-use building. This is in CA 2019 code (IBC 2018). I'm really pondering two exterior exit stairs (and nothing else) for the project.

I want to place both stairs closer than 10' to the side lot lines. I don't have any planning setbacks and don't want to give up the floor area.

It seems like I would be providing equivalent protection (to an enclosed stair) by adding a 2HR wall between the property line and the stair. Three images are attached. One showing the condition without this "extra" wall and one with it.

Is the image with the extra wall along the property line protecting the stair a legit exterior exit stair? I don't see any exceptions in the code that say "10' separation unless you add a 2hr wall in-between" so I'm not sure how I would justify it.

Another thought... If I put a rated lid on the stair (third image) it's basically an enclosed interior stairwell, isn't it? There is no fire rating requirement for the side facing the public way...

Maybe the problem with the second image is that I haven't provided any protection to the "lid" of the stair from a fire on the neighbors property?

Any insights would be appreciated.
 

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Not a California guy here, but my take would be that you cannot classify the proposed as an exterior exit stairway. Per CBC 1027.5, the minimum fire separation distance is 10-ft. As your proposed design only provides 5-ft to the adjoining lot, an exterior exit stairway is a no-go.

1027.5 Location
Exterior exit stairways and ramps shall have a minimum fire separation distance of 10 feet (3048 mm) measured at right angles from the exterior edge of the stairway or ramps, including landings, to:
  1. Adjacent lot lines.
  2. Other portions of the building.
  3. Other buildings on the same lot unless the adjacent building exterior walls and openings are protected in accordance with Section 705 based on fire separation distance.
For the purposes of this section, other portions of the building shall be treated as separate buildings.

Exception: Exterior exit stairways and ramps serving individual dwelling units of Group R-3 shall have a minimum fire separation distance of 5 feet (1525 mm).

​
That then leaves you classifying it as an interior exit stairway that is located on an exterior wall. Exterior walls must meet the fire-resistance rating requirements of Table 602. This would (given some assumptions) only require 1-hr rated construction (which you should already be doing for that wall line).
 
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Ty J - would you agree that option 3 is a legit "interior exit stairway"? It's enclosed on three sides and has a lid, all 2HR rated. The fourth "open" side is facing the public way, a wall that has no rating requirement.
 
nealderidder said:
Ty J - would you agree that option 3 is a legit "interior exit stairway"? It's enclosed on three sides and has a lid, all 2HR rated. The fourth "open" side is facing the public way, a wall that has no rating requirement.
Click to expand...
I would not. The 'open' forth side indicates to me that it is still an exterior exit stairway that has the one open side as required.

If you desire to have an interior exit stairway, then you have to meet all the requirements of CBC Section 1023. This is traditionally a fully enclosed complete shaft assembly with ventilation. Section 1023.7 (below) provides specific exemptions for how to treat the exterior wall.

1023.7 Interior exit stairway and ramp exterior walls
Exterior walls of the interior exit stairway or ramp shall comply with the requirements of Section 705 for exterior walls. Where nonrated walls or unprotected openings enclose the exterior of the stairway or ramps and the walls or openings are exposed by other parts of the building at an angle of less than 180 degrees (3.14 rad), the building exterior walls within 10 feet (3048 mm) horizontally of a nonrated wall or unprotected opening shall have a fire-resistance rating of not less than 1 hour. Openings within such exterior walls shall be protected by opening protectives having a fire protection rating of not less than 3/4 hour. This construction shall extend vertically from the ground to a point 10 feet (3048 mm) above the topmost landing of the stairway or ramp, or to the roof line, whichever is lower.​
 
Wait a minute. Doesn't image stair-2.jpg and stair-3.jpg meet the requirements for an exterior exit stair?
The open side is facing a public way per CBC 1027.4.

I realize 1027.5 says 10' from "property lines", but since 1027.4 says the open side can actually "adjoin" a public way, wouldn't this indicate that 1027.5 only intended to address property lines between private properties, not the PL at a public right of way?
 
Yikes said:
Wait a minute. Doesn't image stair-2.jpg and stair-3.jpg meet the requirements for an exterior exit stair?
The open side is facing a public way per CBC 1027.4.

I realize 1027.5 says 10' from "property lines", but since 1027.4 says the open side can actually "adjoin" a public way, wouldn't this indicate that 1027.5 only intended to address property lines between private properties, not the PL at a public right of way?
Click to expand...
My concern would be spread of fire from the adjoining property that is 5-ft away affecting egress through the exterior exit stairway. The code does not state that the open side must be 10-ft, but that the stairway shall be 10-ft. All three of the proposed designs utilize an open side that is required per an exterior exit stairway; the fire separation distance of the stairway to the property line does not change and remains 5-ft.

1027.5 Location
Exterior exit stairways and ramps shall have a minimum fire separation distance of 10 feet (3048 mm) measured at right angles from the exterior edge of the stairway or ramps, including landings, to:
  1. Adjacent lot lines.
  2. Other portions of the building.
  3. Other buildings on the same lot unless the adjacent building exterior walls and openings are protected in accordance with Section 705 based on fire separation distance.
For the purposes of this section, other portions of the building shall be treated as separate buildings.

Exception: Exterior exit stairways and ramps serving individual dwelling units of Group R-3 shall have a minimum fire separation distance of 5 feet (1525 mm).​

I'd encourage a discussion with the AHJ and see what they may approve.
 
[QUOTE="If you desire to have an interior exit stairway, then you have to meet all the requirements of CBC Section 1023. This is traditionally a fully enclosed complete shaft assembly with ventilation.
[/QUOTE]

This really gets to the heart of it. When does an exterior stair become an interior stair. #1 is obviously "exterior". #2 is probably "exterior" because it doesn't have a lid. But #3 has a lid and the wall facing the public way could be all non-rated glazing. So why couldn't I just remove that non-rated glazing and leave it open?

Thank you all for the input!
 
I would say that "interior" suggests some protection (fire, smoke, heat, weather, sprinklers) even though there is not a specified level or requirement; and exterior, no protection is assumed....
 
I don't know if the CBC has similar wording, but it might be difficult to meet the open side requirements of IBC 1027.3 for openings "adjacent to each floor level and the level of each intermediate landing."
 
Hi everyone,

I found this thread similar to my situation, where did it end up with the permits?

To give some context. I am building (designing) an ADU on the second floor of a single family home with an exterior stairway on the side of the lot as the ADU entrance. Something like this with the first floor being the main house and ADU on top, and the stairway 5' to property line. Is there a way to implement this idea?
1705079797212.png
 
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