Chair Lift Egress Width

[jar546]

What is the minimum width of a front porch stairwell when the stairwell serves an exit? How much do you limit its encroachment into the stairwell width?

 

[classicT]

Is the stairwell serving a single dwelling unit or multiple? Single dwelling unit, 20-inches. Common (shared) stairway, 36-inches for up to OL of 50.

See IBC 1011.2.

1011.2 Width and Capacity
The required capacity of stairways shall be determined as specified in Section 1005.1, but the minimum width shall be not less than 44 inches (1118 mm). See Section 1009.3 for accessible means of egress stairways.
Exceptions:

1. Stairways serving an occupant load of less than 50 shall have a width of not less than 36 inches (914 mm).
2. Spiral stairways as provided for in Section 1011.10.
3. Where an incline platform lift or stairway chairlift is installed on stairways serving occupancies in Group R-3, or within dwelling units in occupancies in Group R-2, a clear passage width not less than 20 inches (508 mm) shall be provided. Where the seat and platform can be folded when not in use, the distance shall be measured from the folded position.

Do note that exception #3 only applies to private stairways serving a single dwelling unit (within a R-2 dwelling unit, or an R-3).

 

[cda]

IRC question??

 

[jar546]

Is the stairwell serving a single dwelling unit or multiple? Single dwelling unit, 20-inches. Common (shared) stairway, 36-inches for up to OL of 50.

See IBC 1011.2.

1011.2 Width and Capacity
The required capacity of stairways shall be determined as specified in Section 1005.1, but the minimum width shall be not less than 44 inches (1118 mm). See Section 1009.3 for accessible means of egress stairways.
Exceptions:

1. Stairways serving an occupant load of less than 50 shall have a width of not less than 36 inches (914 mm).
2. Spiral stairways as provided for in Section 1011.10.
3. Where an incline platform lift or stairway chairlift is installed on stairways serving occupancies in Group R-3, or within dwelling units in occupancies in Group R-2, a clear passage width not less than 20 inches (508 mm) shall be provided. Where the seat and platform can be folded when not in use, the distance shall be measured from the folded position.

Do note that exception #3 only applies to private stairways serving a single dwelling unit (within a R-2 dwelling unit, or an R-3).

This is a Townhouse so for right now, the IBC does not apply.

 

[classicT]

Good question CDA, I missed that this was in the Res. Codes section.

If this is an IRC structure, then I propose that IRC Section R311.1 does not require that the exterior stairways be accessible. The means of egress is only required to get you to the egress door. Once out of the structure, Section R311 does not apply.

R311.1 Means of Egress
Dwellings shall be provided with a means of egress in accordance with this section. The means of egress shall provide a continuous and unobstructed path of vertical and horizontal egress travel from all portions of the dwelling to the required egress door without requiring travel through a garage. The required egress door shall open directly into a public way or to a yard or court that opens to a public way.

However, if you wish, apply IRC Section R311.7.1 to require a minimum of 36-inches.

R311.7.1 Width
Stairways shall be not less than 36 inches (914 mm) in clear width at all points above the permitted handrail height and below the required headroom height. Handrails shall not project more than 4 1/2 inches (114 mm) on either side of the stairway and the clear width of the stairway at and below the handrail height, including treads and landings, shall be not less than 31 1/2 inches (787 mm) where a handrail is installed on one side and 27 inches (698 mm) where handrails are provided on both sides.

Exception: The width of spiral stairways shall be in accordance with Section R311.7.10.1.

This really leaves you with three options:

1. Egress has been met per R311.1, therefore no requirement exists.
2. Apply R311.7.1 and require a minimum unobstructed width of 36-inches (27 or 31-1/2-in below the handrail depending on handrail configuration).
3. Or, apply the provisions of the IBC Section 1011.2 and require 20-inches as an alternate means given that the IRC fails to address this specific condition.

I'd recommend that applying IBC Section 1011.2 to allow a 20-inch clear passage. It is a defensible alternate means and method that allows the most flexibility to the owner, while still being grounded in the code.