Residential components of Mixed Use - Stair Components

[tomtomtom]

We are renovating an existing second story apartment into two units, in a conforming mixed use building (two commercial units on the first floor, two apartments on the second).
There is an interior stair which exits outdoors, which will serve one unit: existing no change.
The second unit will be served by an exterior staircase: the existing one is non-conforming, and will be replaced: this stair serves only a single apartment/unit, and goes from the second floor unit to a parking lot: consensus in our office, and with a code consultant is that this is a residential component and can be built, as the existing interior stair, to IRC, not IBC- the building official has stated that he believes it should be built per IBC stair requirements: which is a lot of stair for a an apartment with an occupant load under five people..
I do not see an explicit code exception for this, but then, we also don't need to follow commercial plumbing code for the residential unit... so I'm looking for something definitive in terms of interpretation or explicit exception to end the conversation.

 

[Sifu]

I recently reviewed a set of plans for an R2 unit above another R2 unit. My first reaction was to require the riser and treads per the IBC because they were in the building envelope and my belief was that the exception was only for interior stairs within a unit that only provided travel between floors within the unit, but it didn't sit well with me. So I dug in and decided the code didn't support that idea. In this case the stairs from the unit above are entirely within the unit and separated by the required rated assemblies. They begin on a lower floor landing separated from the adjacent unit. I fell back on the intent of the code to aid in my thinking that this was not necessary. The intent is for low occupant load and occupant familiarity. In your case the stairs are not "within" the unit, but the same conditions apply since the users of the stair would experience the exact same thing as if the stair was "within" the unit like the building I looked at. I accepted the IRC tread and riser dimensions.

I had another building type, in the same development with an exterior exit stairway that served two units. It correctly followed the IBC requirements....except now they have an exterior exit stair that must comply with IBC IBC 1027, which it did not. So you may want to take a look at that code section.

The BO may be hung up on "within", and it may be a hard argument to counter, but if they only serve the unit above and the only difference is that they are not bounded by walls that would make them "within" the unit I think I would be ok with them. Unfortunately, my opinion isn't a definite interpretation for the BO, it is just my opinion.

 

[tomtomtom]

I recently reviewed a set of plans for an R2 unit above another R2 unit. My first reaction was to require the riser and treads per the IBC because they were in the building envelope and my belief was that the exception was only for interior stairs within a unit that only provided travel between floors within the unit, but it didn't sit well with me. So I dug in and decided the code didn't support that idea. In this case the stairs from the unit above are entirely within the unit and separated by the required rated assemblies. They begin on a lower floor landing separated from the adjacent unit. I fell back on the intent of the code to aid in my thinking that this was not necessary. The intent is for low occupant load and occupant familiarity. In your case the stairs are not "within" the unit, but the same conditions apply since the users of the stair would experience the exact same thing as if the stair was "within" the unit like the building I looked at. I accepted the IRC tread and riser dimensions.

I had another building type, in the same development with an exterior exit stairway that served two units. It correctly followed the IBC requirements....except now they have an exterior exit stair that must comply with IBC IBC 1027, which it did not. So you may want to take a look at that code section.

The BO may be hung up on "within", and it may be a hard argument to counter, but if they only serve the unit above and the only difference is that they are not bounded by walls that would make them "within" the unit I think I would be ok with them. Unfortunately, my opinion isn't a definite interpretation for the BO, it is just my

 

[tomtomtom]

Right- and there is no “within” language in reference for r-3, I don’t understand what room there is for him to disagree with this:
“
1011.5.2 exception 5 (page #37)
". In Group R-1 bed and breakfast establishments; in Group R-3 occupancies; within dwelling units in Group R-2 occupancies; and in Group U occupancies that are accessory to Group R-3 occupancy, or accessory to individual dwelling units in Group R-2 occupancies; the maximum riser height shall be 8 ¼ inches (209.5 mm) and the minimum tread depth shall be 9 inches (229 mm); the minimum winder tread depth at the walkline shall be 10 inches (254 mm); and the minimum winder tread depth shall be 6 inches (152 mm). A nosing not less than ¾ inch (19.1 mm) but not more than 1 ¼ inches (32 mm) shall be provided on stairways with solid risers where the tread depth is less than 11 inches (279 mm). “

 

[JMarsh]

consensus in our office, and with a code consultant is that this is a residential component and can be built, as the existing interior stair, to IRC, not IBC-

See R101.2 Scope of the IRC and 101.2 Scope of the IBC.

The IRC covers "detached one- and two-family dwellings and townhouses...." However, exception R101.2 No. 1 does cover Live/work units meeting IBC 419.

Unless these units meet IBC 419, I don't see them as "detached" -- and so they would be covered by the IBC as a Mixed Use Building. If they are Live/work per IBC 419, they would still be treated as R2 and not R3 (per 419.2). The IRC specifies that a Live/work unit must meet the entirety of IBC 419.

 

[tbz]

Here in lies the true questions

• Within R2 is specific because others besides the resident within the unit have access to stairways, not within the unit itself, hence common areas.
• R3's are mainly single-family units above 3 stories that don't qualify for IRC status and they can be attached or detached but are served by a singular lot.

So in your case, with it being an R2 the exterior stairway is considered common area on the whole property, though it might only serve one unit everyone has access to the exterior of the property.

I know it is splitting hairs, but I was part of the conversation when the CTC 10-15 years ago went through this specific language for the intent of the hair splitting.

Unless there is not enough room on the exterior envelope of the existing property because a 7x11 run out will exceed the room for it, the cost difference between the manufacture and installation of the stair portion only is very minimal.

The question becomes the additional cost for having 2 handrails and the 42" guard, vs just a 36" guard with the top serving as the single handrail requirement.

Then there is exception one that came in I believe in 2015 for 1015.3 height which allows the guards for R3's and within R2's to be reduced to 36-inches when the unit is not more than 3 stories above grade with a separate entrance serving it. You could argue that the guard need only be 36-inches on that flight and the top serve as the handrail and then only need the wall side to have the second handrail and reduce cost that way, but splitting hairs again.

But, let me ask the following?

• If the base minimum standard in the IBC is for a maximum of a 7-inch riser with a minimum tread depth of 11-inches and
• The model IRC supports a lower minimum tread depth of 10-inches with a higher maximum riser of 7.75-inches, the first concession
• And CT amended the IRC requirements to an even lesser requirement of a minimum tread depth of 9-inches with a higher maximum riser of 8.25-inches
  • Please tell the members of the jury how you got to this R2 being an R3 and why you even looked to make the entrance less safe than safer?

 

[tomtomtom]

Here in lies the true questions

• Within R2 is specific because others besides the resident within the unit have access to stairways, not within the unit itself, hence common areas.
• R3's are mainly single-family units above 3 stories that don't qualify for IRC status and they can be attached or detached but are served by a singular lot.

So in your case, with it being an R2 the exterior stairway is considered common area on the whole property, though it might only serve one unit everyone has access to the exterior of the property.

I know it is splitting hairs, but I was part of the conversation when the CTC 10-15 years ago went through this specific language for the intent of the hair splitting.

Unless there is not enough room on the exterior envelope of the existing property because a 7x11 run out will exceed the room for it, the cost difference between the manufacture and installation of the stair portion only is very minimal.

The question becomes the additional cost for having 2 handrails and the 42" guard, vs just a 36" guard with the top serving as the single handrail requirement.

Then there is exception one that came in I believe in 2015 for 1015.3 height which allows the guards for R3's and within R2's to be reduced to 36-inches when the unit is not more than 3 stories above grade with a separate entrance serving it. You could argue that the guard need only be 36-inches on that flight and the top serve as the handrail and then only need the wall side to have the second handrail and reduce cost that way, but splitting hairs again.

But, let me ask the following?

• If the base minimum standard in the IBC is for a maximum of a 7-inch riser with a minimum tread depth of 11-inches and
• The model IRC supports a lower minimum tread depth of 10-inches with a higher maximum riser of 7.75-inches, the first concession
• And CT amended the IRC requirements to an even lesser requirement of a minimum tread depth of 9-inches with a higher maximum riser of 8.25-inches
  • Please tell the members of the jury how you got to this R2 being an R3 and why you even looked to make the entrance less safe than safer?

There seems to be some confusion on your part, or maybe I'm confusing the "voice" of your writing:
as the OP, the project I am referring to is an existing r-3: Two story building, 2 apartments on the second floor, 2x commercial units on the first floor.
The existing stair we are replacing is entirely non-conforming, we are looking to build a new stair that is appropriate and reasonable for a r-3 use with low occupant load providing egress from the second story.

 

[Sifu]

I mis-read the OP, and was assuming they were R2. If an R3, you are correct that the "within" laguage is not there. I would say if you were using the IBC then the exception allowing the IRC risers/treads might apply. CT amendments aside, it would appear that use of the residential provisions would apply as well. Unless the BO is now just hung up on "IN"!

I understand TBZ's assertion that the exterior stair would be available to a non-resident, such as a UPS driver or a Jehovah's Witness, and it sounds like he may have a better understanding of the original intent in this regard. But as written, I could see it your way as well. You may consider a technical opinion or interpretation from your code authority if doing it the BO's way is too much of a hardship. If so, let us know the outcome.

 

[tomtomtom]

I mis-read the OP, and was assuming they were R2. If an R3, you are correct that the "within" laguage is not there. I would say if you were using the IBC then the exception allowing the IRC risers/treads might apply. CT amendments aside, it would appear that use of the residential provisions would apply as well. Unless the BO is now just hung up on "IN"!

I understand TBZ's assertion that the exterior stair would be available to a non-resident, such as a UPS driver or a Jehovah's Witness, and it sounds like he may have a better understanding of the original intent in this regard. But as written, I could see it your way as well. You may consider a technical opinion or interpretation from your code authority if doing it the BO's way is too much of a hardship. If so, let us know the outcome.

Thank You,
The Code expert I'm working with suggested that providing signage ~"Privacy" was not sufficient to totally eliminate the probability of public use, so suggested a gate at the bottom of the stair/ if the bo was relentless.

 

[Paul Sweet]

Will they consider a code modification to say "within or serving only one dwelling unit"?
The IBC was written to consider most common configurations where an outside stair would serve multiple units. This is similar to an uver/under duplex under the IRC, where delivery people and other callers would use a stair meeting the IRC and not the IBC.
It would be best to use the IBC tread & riser dimensions if there is room.

 

[tbz]

If the units are a R3 and the stairway only serves the single unit, nothing else, then you could use exception 2 on the exterior, per say.

My question is why reduce the safety if you have the room for the 7x11 stair treads, anyone telling you the cost is drastic, I would argue After 30 plus years of fabricating stairs that there is really no significate cost savings on an exterior stair flight. Its the handrails and guard requirements that drive up the cost when you go from 36 to 42 for the guard and then can't use the top and have to add a second handrail.

So, my question is what do you consider "a lot of stair" and why?

The way I see it, I like simple when I explain my designs to 12 in a box with my choice.

 

[JMarsh]

The second unit will be served by an exterior staircase: the existing one is non-conforming, and will be replaced: this stair serves only a single apartment/unit, and goes from the second floor unit to a parking lot:

The IEBC has an exception if there is not enough room to make a stair alteration work with lower risers and deeper treads. I'm not sure if this "fits" your particular situation.

2018 IBC > 503.1 General, Exception 1: An existing stairway shall not be required to comply with the requirements of 1011 of the IBC where the existing space and construction does not allow a reduction in pitch and slope.

There is no reference in this exception to "within" and, it excludes the entirety of 1011. I think a case could be made that if a stair works now - even if nonconforming - little would be gained by replacing it.

 

[steveray]

The building cannot be both IRC and IBC....Putting a door at the bottom of the stair would solve it or the IEBC could be your friend, but that is all stuff your "code expert" should know....