Stair width requirement comment

[spabilove]

I am working on a base building plan for a future retail tenant, which includes two egress stairs and one elevator serving the 2nd floor. I received the following comment:

"The egress width at the base of the rear stairs appears inadequate to support the occupant load from the 2nd floor, as well as the combined occupant loads of tenants 1-A and 1-B. Please demonstrate compliance and provide calculations (2018 VCC 1005.3.2, 1005.6)."

My understanding is that I need to provide 0.2 inches of egress width per occupant if the building is sprinklered. I have designed the 2nd floor for Mercantile use, with a total occupancy load of 319 people, resulting in a required egress width of 63.8 inches.

I have two stairs: one with a width of 5 feet and the other with a width of 9 feet 8 inches. Based on my calculations, it seems that I am 3.8 inches short of the required width. I am wondering if this shortfall could be waived, given that the other stair exceeds the requirement.

 

[Yankee Chronicler]

"The egress width at the base of the rear stairs appears inadequate to support the occupant load from the 2nd floor, as well as the combined occupant loads of tenants 1-A and 1-B. Please demonstrate compliance and provide calculations (2018 VCC 1005.3.2, 1005.6)."

Unless Virginia changed something, you don't have to accommodate the second floor occupant load plus any of the first floor occupant load. The underlying assumption is that by the time people from the second floor reach the first floor, most of the people on the first floor will already have exited the building. From the Virginia building code:

1005.6 Egress Convergence. Where the means of egress from stories above and below converge at an intermediate level, the capacity of the means of egress from the point of convergence shall be not less than the largest minimum width or the sum of the required capacities for the stairways or ramps serving the two adjacent stories, whichever is larger.

Here's the ICC Commentary on that section:

Convergence of occupants can occur wherever the
occupants of an upper floor travel down and occupants
of a lower floor travel up and meet at a common, intermediate
egress component on the route to the exit discharge.
The intermediate component may or may not
be another occupiable floor and, most often, is an exit
door [see Commentary Figures 1005.6(1) and
1005.6(2)].
The entire premise of egress convergence is based
on the assumption of simultaneous notification (i.e., all
occupants of all floors begin moving toward the exits at
the same time). As illustrated in Commentary Figure
1005.6(3), the occupants of the first floor will have
exited the building by the time most of the occupants
of the second floor have reached the exit discharge
door. However, as illustrated in Commentary Figure
1005.6(1), the occupants of a basement will reach the
discharge door simultaneously with the second-floor
occupants, thereby creating a bottleneck and the need
for sizing the affected component for a larger combined
occupant load.
An egress convergence situation can also be created
where an intermediate floor level is not present,
as illustrated in Commentary Figure 1005.6(2). Again,
under the assumption of simultaneous notification,
occupants of both floors would reach the exit discharge
door at approximately the same time, invoking
the requirements for increased egress capacity.

And here's the accompanying diagram:



Note that in Figure 1005.6(1), the converging stories are the second floor and the basement. The illustration does NOT include a third vector representing the occupants from the first floor converging with the occupants from the basement and the second floor.

That said -- your exit access distance measurements are incorrect. Exit access travel is not measured on diagonals, because it has to take into account walking around furniture and other obstacles. Both the IBC Commentary and the NFPA 101 Handbook tell us to measure on rectilinear axes. Also, your starting pints in most of the rooms aren't the points farthest from the doors leading out of those spaces.

 

[Tim Mailloux]

If I read your original post correctly, you have (2) stairs totaling 176” of exit width, at .2” per person in a sprinklered building those two stairs can accommodate 880 people.

If we want to get technical, your large stair can only accommodate 300 people (the same as the small stair) due to 1005.5…but that still gives you a max floor capacity of 600 people

1005.5 Distribution of minimum width and required capacity. Where more than one exit, or access to more than one exit, is required, the means of egress shall be configured such that the loss of any one exit, or access to one exit, shall not reduce the available capacity or width to less than 50 percent of the required capacity or width.

 

[Yankee Chronicler]

It also appears that both stairs are open, not enclosed exits. Not allowed.

 

[Yankee Chronicler]

I am working on a base building plan for a future retail tenant, which includes two egress stairs and one elevator serving the 2nd floor. I received the following comment:

"The egress width at the base of the rear stairs appears inadequate to support the occupant load from the 2nd floor, as well as the combined occupant loads of tenants 1-A and 1-B. Please demonstrate compliance and provide calculations (2018 VCC 1005.3.2, 1005.6)."

My understanding is that I need to provide 0.2 inches of egress width per occupant if the building is sprinklered. I have designed the 2nd floor for Mercantile use, with a total occupancy load of 319 people, resulting in a required egress width of 63.8 inches.

I have two stairs: one with a width of 5 feet and the other with a width of 9 feet 8 inches. Based on my calculations, it seems that I am 3.8 inches short of the required width. I am wondering if this shortfall could be waived, given that the other stair exceeds the requirement.

I don't understand your math. At 319 occupants and 0.2" per person, the required width is 63.8 inches. So far, so good.

But then you spell out stair widths of 5 feet and 9'-8", which is a total of 176 inches -- and you then say you have a shortfall. 176 is a lot more than 63.8, so what's the shortfall?

 

[LR419]

"The egress width at the base of the rear stairs appears inadequate to support the occupant load from the 2nd floor, as well as the combined occupant loads of tenants 1-A and 1-B. Please demonstrate compliance and provide calculations (2018 VCC 1005.3.2, 1005.6)."

The review comment doesn't say that the stair itself is the problem. It may be the distance between the bottom riser and the ramp railing, which looks a bit tight. Or it may be the width of the exterior doors. And speaking of doors, there's a slew of them swinging the wrong direction (see 1010.1.2.1).

I don't see a problem with the open stairs, though. If it's a two story building that should be allowed by 1019.3 Exception 1, provided the exit access travel distance is not exceeded.

 

[Yankee Chronicler]

I don't see a problem with the open stairs, though. If it's a two story building that should be allowed by 1019.3 Exception 1, provided the exit access travel distance is not exceeded.

Open stairs as means of egress are exit access, not exits. The exit access travel distance thus has to be measured from the most remote point on the second story to the stair, down the stair, and to the exit door on the first floor.

The exit access travel distance in rooms and spaces is not to be measured along diagonals.

 

[Yankee Chronicler]

Also, all of the tenant spaces on the ground floor and one of the tenant spaces on the second floor have occupant loads exceeding 50.

 

[Paul Sweet]

It looks like the landing between the bottom of the rear stairs and the railing around the lower vestibule is inadequate, especially once the one tread width railing extension is added.

The rear stair risers appear to be perpendicular to the line of travel on the second floor plan, but skewed on the first floor plan.

 

[Yankee Chronicler]

The rear stair risers appear to be perpendicular to the line of travel on the second floor plan, but skewed on the first floor plan.

Good catch! I missed that.

 

[Penguin87]

It also appears that both stairs are open, not enclosed exits. Not allowed.

The larger stair appears to be enclosed?

Also, besides the wrong-way swinging doors at each tenant, you are not supposed to run your travel distance at an angle - it should be orthogonal.

 

[walker.t]

My understanding is that I need to provide 0.2 inches of egress width per occupant if the building is sprinklered.

"The egress width at the base of the rear stairs appears inadequate

The 0.2” is in reference to the width of stairs per 1005.3.1 Exception 1. But the comment “at the base” seems to me to be indicating the distance between the bottom stair riser and the ramp, not the width of the stair.

The rear stair risers appear to be perpendicular to the line of travel on the second floor plan, but skewed on the first floor plan.

I have only seen straight flights of stairs with nosings at a right angle to the handrails, I didn’t know such a skewed configuration was allowed.

It may be the distance between the bottom riser and the ramp railing, which looks a bit tight.

I tried to scale this plan using the given 5’ distance between handrails as my reference, I measured 3’-11” from the bottom riser to the ramp, so I’ll assume that’s 4’. 1011.6 (Stairway Landings) requires a landing equal to the width of the stair or 48” whichever is less, but as you mention the handrail extensions aren’t shown which will reduce the width of the passage between the stairs and the ramp.

I am working on a base building plan

A few additional comments…

The first floor plan doesn’t show the lines indicating the ramp landing at the change of direction in the corner. ADA 405.7.4 and IBC 1012.6.4 both require a 60”x60” landing at changes in direction at ramps.

My understanding of IBC 1004.2.1 (Intervening Spaces of Accessory Areas) is that you’ll need to size the ramp so it has capacity for the four first floor tenant spaces and the stairs.

You might have a typographical error on the sheet with the second floor plan. Above the “Occupant Load and Means of Egress Requirements” table you have a small table titled “1016.2 Exit Travel Distance”, maybe that’s supposed to say “Exit Access Travel Distance”? The 2018 IBC has 1017 Exit Access Travel Distance with Table 1017.2 Exit Access Travel Distance.

You are showing a 4-riser stairway at the bottom-left corner of the first floor plan, you don’t show handrails, the handrail extension is going to project into the door opening to the exterior. Also, check your door maneuvering clearance for the door at the top of those stairs, you need 24” on the latch side and 42” measured perpendicular to the wall per A117.1-2009 Table 404.2.3.2.

 

[Yankee Chronicler]

The larger stair appears to be enclosed?

It does not appear to be enclosed to me. Not at all.

 

[Yankee Chronicler]

Unrelated to egress -- the toilet rooms for tenants 1B and 1C are too small.