# Stair Framing:  Primary Structural Frame or Not?



## RLGA (Mar 13, 2012)

Assumption:  Table 601 requires a fire-resistance rating for primary structural frame.

Couple of conditions:

Interior Stairs:  Located within an exit enclosure.  Steel framing for stairs (consisting of columns, stringers, etc.) is independent of the building frame and does not support the enclosure walls.

Exterior Stairs:  Steel framing for stairs (consisting of columns, stringers, etc.) is independent of the building frame and is exterior of the building envelope (i.e. free-standing with landings connected to building).

Would you consider one or both of the two conditions part of the "Primary Structural Frame" as defined by the IBC?  The definition is not clear in this respect, so I'd though I'd get some opinions.


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## steveray (Mar 14, 2012)

I would say no...as the stairs do not resist any forces (wind, snow, seismic I guess) or support anything but themselves (and the users of course)....wouldn't be the first time I was wrong.....just the first time today....


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## gbhammer (Mar 14, 2012)

I see what you’re asking and would say... I would consider the columns of the self supporting stair and the landings connected to those columns as primary construction, even though they are not apart of the building they still need to resist gravity loads.


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## brudgers (Mar 14, 2012)

gbhammer said:
			
		

> I see what you’re asking and would say... I would consider the columns of the self supporting stair and the landings connected to those columns as primary construction, even though they are not apart of the building they still need to resist gravity loads.


  So does the hanger for a sink.


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## gbhammer (Mar 14, 2012)

PRIMARY STRUCTURAL FRAME. The primary structural frame shall include the following;

1.The columns;

2.Structural members having direct connections to the columns, including girders, beams, trusses, and spandrels;

3.Members of the floor construction, and roof construction having direct connections to the columns; and

4.Bracing members that are essential to the vertical stability of the primary structural frame under gravity loading shall be considered part of the primary structural frame whether or not the bracing member carries gravity loads.



			
				RLGA said:
			
		

> Interior Stairs:  Located within an exit enclosure.  Steel framing for stairs (consisting of columns, stringers, etc.) is independent of the building frame and does not support the enclosure walls.
> 
> Exterior Stairs:  Steel framing for stairs (consisting of columns, stringers, etc.) is independent of the building frame and is exterior of the building envelope (i.e. free-standing with landings connected to building).
> 
> ...


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## gbhammer (Mar 14, 2012)

Sorry about that brudgers the daughter and I have had the stomach flue and puke has been on my mind a lot the last two days.


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## Codegeek (Mar 14, 2012)

I'm with steveray on this.  I'd say no they are not primary structural frame members.  They may be part of the secondary members though.


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## imhotep (Mar 14, 2012)

RLGA said:
			
		

> Assumption:  Table 601 requires a fire-resistance rating for primary structural frame.Couple of conditions:
> 
> Interior Stairs:  Located within an exit enclosure.  Steel framing for stairs (consisting of columns, stringers, etc.) is independent of the building frame and does not support the enclosure walls.
> 
> ...


I would say they are not part of the Primary Structural frame.  They are not a fundamental component of the building construction.


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## steveray (Mar 14, 2012)

I would definetely not slight their importance,....but if they were considered primary..might they need to be rated per Table 601? Just as a different perspective....


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## north star (Mar 14, 2012)

*&*

If the stairs are part of the MOE, then I would say "yes" they

would be required to be fire protected.

From the `06 IBC: *EXIT.* That portion of a means of egress system

which is separated from other interior spaces of a building or

structure by fire-resistance-rated construction and opening

protectives as required to provide a protected path of egress travel

between the exit access and the exit discharge.......Exits include

exterior exit doors at ground level, exit enclosures, exit passageways,

exterior exit stairs, exterior exit ramps and horizontal exits.......IMO,

this would also include any interior stairways designated for the MOE.

*=*


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## brudgers (Mar 14, 2012)

steveray said:
			
		

> I would definetely not slight their importance,....but if they were considered primary..might they need to be rated per Table 601? Just as a different perspective....


  Yes they would be required to be rated if they were considered that way.  However, such consideration would be incorrect.


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## Codegeek (Mar 14, 2012)

If the stairs have elements which connect to the columns or other structural elements, then they would be considered primary structural members.  From what the OP states, it appears they do not, so they would not be primary structural members.  Yes, the stairs may have gravitational forces on them, but they are not part of the primary structural members.


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## north star (Mar 14, 2012)

*=*



Does the term "primary structural members" hinge on means of attachment,

or use?......Either way, the MOE stairs would still require fire protection.

*=*


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## Francis Vineyard (Mar 14, 2012)

The new requirement clarifies the intent that the primary structural columns are individually wrapped or protected and other frame members can continue to be protected within the fire-resistant membrane assembly. The fire-resistance of the stairway framing was not affected.

Francis


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## Codegeek (Mar 14, 2012)

north star said:
			
		

> *=*
> 
> Does the term "primary structural members" hinge on means of attachment,
> 
> ...


This is from the 2009 IBC Commentary - "This category includes the structural (load-bearing) components of the building frame. Definitions of “Primary structural frame” and “Secondary members” are found in Section 202. Any structural item that provides direct connections to columns and bracing members that are designed to carry a gravity load is considered part of the structural frame."

It goes on to say, "Secondary members (e.g., floor or roof panels _without a connection to the column_) are not considered part of the structural frame."

The definition of secondary members -

"SECONDARY MEMBERS. The following structural members shall be considered secondary members and not part of the primary structural frame:

1. Structural members not having direct connections to the columns;

2. Members of the floor construction not having direct connections to the columns; and

3. Bracing members other than those that are part of the primary structural frame."


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## gbhammer (Mar 14, 2012)

Codegeek said:
			
		

> If the stairs have elements which connect to the columns or other structural elements, then they would be considered primary structural members.  From what the OP states, it appears they do not, so they would not be primary structural members.  Yes, the stairs may have gravitational forces on them, but they are not part of the primary structural members.


Primary Stucture does not mean the building.

Primary structure = column/elements that supports vertical structure from gravity loads.

The stair is a structure that resist gravity loads


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## gbhammer (Mar 14, 2012)

All right I agree with ya'll now after seeing the secondary structure def.


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## steveray (Mar 14, 2012)

Sorry for throwing in that rating thing....I think I muddied it up a bit....I was just trying to make the point that if they were considered part of the primary structure, the stairs themselves would need to be rated (by table 601 me thinks), as well as the vertical exit enclosure....maybe I am wrong, but I have never seen 1 hr stringers inside a 1 hr enclosure...


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## Francis Vineyard (Mar 14, 2012)

In reference to the OP conditions; if the "independent" supporting columns for the stairs where to be individually wrapped in fire-resistance protection with the stairway exposed to extreme heat; would render the protection application and exit useless.

Francis


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## TheCommish (Mar 14, 2012)

http://www.inspectpa.com/forum/showthread.php?7704-Fire-resistive-construction-of-a-unenclosed-monumental-stair

Not fire resitive but non combustable 2009 IBC 1009.6 Stairway construction. All stairways shall be built of materials consistent with the types permitted for the type of construction of the building, except that wood handrails shall be permitted for all types of construction.

Then SECTION 603 COMBUSTIBLE MATERIAL IN TYPE I AND II CONSTRUCTION 603.1 Allowable materials. Combustible materials shall be permitted in buildings of Type I or II construction in the following applications and in accordance with Sections 603.1.1 through 603.1.3: the list 25 allowance and exception none of which are stair stringers, guards or supports


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## JBI (Mar 15, 2012)

The short answer is No, the stair components described are not a part of the primary structural fram of the building for the application of table 601. The enclosure requirements are found in other chapters, and the required exit stairs will likely require enclosure/protection, not as components of the Primary Structural Frame but rather as components of the Means Of Egress.


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## redeyedfly (Apr 23, 2021)

Old post but I was helping with a code alternate and this came up. in my google search.


Code commentary to Section 1011.7:

_In keeping with the different levels of fire protection provided by each of the five basic types of construction designated in Chapter 6, the materials used for stairway construction must meet the appropriate combustibility/noncombustibility requirements indicated in Section 602 for the particular type of construction of the building in which the stairway is located. This is required whether or not the stair is part of the required means of egress. Any structure supporting the stairway and the stairway enclosure must be fire-resistance rated consistent with the construction type; however, the stairway components inside the enclosure need only comply with the material limits for the type of construction._

Stairways are not required to be FRR.  What would be the point?  If there's already fire in the stair shaft no one is using it for egress.


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## cda (Apr 23, 2021)

redeyedfly said:


> Old post but I was helping with a code alternate and this came up. in my google search.
> 
> 
> Code commentary to Section 1011.7:
> ...




so they don’t burn???

should not be fire in the stair shaft


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## redeyedfly (Apr 23, 2021)

cda said:


> so they don’t burn???
> 
> should not be fire in the stair shaft


FRR and noncombustible are not the same thing.


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## Mark K (Apr 24, 2021)

This is not a concept used by structural engineers. 

My understanding is that the primary structural frame are those structural elements essential to keeping the building from collapse if the secondary structural elements were damaged by fire.

Remember that there are some building systems that do not necessarily have formal columns which would imply that there was no primary structural frame.  Since the primary frame is often dependent on secondary members to brace the primary structural frame these secondary members would be considered as part of the primary structural frame.


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## sergoodo (Apr 25, 2021)

Mark K said:


> This is not a concept used by structural engineers.
> 
> My understanding is that the primary structural frame are those structural elements essential to keeping the building from collapse if the secondary structural elements were damaged by fire.
> 
> Remember that there are some building systems that do not necessarily have formal columns which would imply that there was no primary structural frame.  Since the primary frame is often dependent on secondary members to brace the primary structural frame these secondary members would be considered as part of the primary structural frame.


Agree not primary with the industry standard for engineering- reflected by CSI which has metal stair structures specified as separately as misc metals. Stair structure misc metal is primary for the life safety function of the building like guardrails etc.

Needs to be cleared up because you can hang hat on either.


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## Mark K (Apr 25, 2021)

The fact that metal stairs are considered miscellaneous metal has nothing to do with safety, use, or performance.

AISC in their code of standard practice makes it clear that metal stairs are not structural steel.  This is a commercial, not a technical, decision.  Steel fabricators focus on fabricating the typical beams and columns.  Other fabricators typically fabricate stairs.  Since the AISC members typically do not fabricate stairs they have excluded stairs from the definition of structural steel which they use to define their scope of work.   In response to this CSI has placed steel stairs in the miscellaneous metals specification section.  This is a commercial scope of work issue that is not based on any technical criteria.

Structural engineers use the same technical standards when designing either the building frame or steel stairs.


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## steveray (Apr 26, 2021)

brudgers said:


> So does the hanger for a sink.



Times like this I miss Brudgers...

I beleive there is a 2024 clarification in on this....



redeyedfly said:


> Stairways are not required to be FRR. What would be the point? If there's already fire in the stair shaft no one is using it for egress.



My thoughts too, but the same reason penetrations are allowed in the outside of the stair, but not the inside...Dumb people are writing the code..

Exception: Membrane penetrations shall be permitted on
the outside of the interior exit stairway and ramp. Such
penetrations shall be protected in accordance with Section
714.3.2.


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## Rick18071 (Apr 26, 2021)

I would think the framing for the stairway is the  primary structural frame for the stairway.


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## ADAguy (Apr 26, 2021)

steveray said:


> I would say no...as the stairs do not resist any forces (wind, snow, seismic I guess) or support anything but themselves (and the users of course)....wouldn't be the first time I was wrong.....just the first time today....


"Wrong" must indeed resist seismic forces.


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## steveray (Apr 26, 2021)

That is why I said "seismic I guess" 8 years ago  ......If it is not supporting the frame...It's not the frame.....

PRIMARY STRUCTURAL FRAME. The primary structural
frame shall include all of the following structural members:
1. The columns.
2. Structural members having direct connections to the
columns, including girders, beams, trusses and spandrels.
3. Members of the floor construction and roof construction
having direct connections to the columns.
4. Bracing members that are essential to the vertical stability
of the primary structural frame under gravity
loading shall be considered part of the primary structural
frame whether or not the bracing member carries
gravity loads.


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## Yikes (Apr 26, 2021)

I'm struggling with this one.  Most of the time, I can see some type of (mostly) intuitive reason as to the life safety rationale, but I don't see it here.
Example: a required exit stair is exterior to the otherwise-enclosed building, and is made of metal (columns, stringers, pans, etc.).  It is bolted to the main combustible building.  We all know that steel loses its structural performance characteristics when it gets hot.
A fire breaks out on or near the stair (picture a bad actor dumping trash on the stair and setting it on fire).

My intuition says that of all the components of a structure, an exit  / exit discharge stair would be one of the most important items to keep operational as long as possible in event of fire.  so why would the columns that support an essential means of egress be allowed to have zero fire resistance rating.


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## Mark K (Apr 26, 2021)

Given the definition of a primary structural frame a structural engineer would not normally consider stair stringers to be part of the primary structural frame.


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## tbz (Apr 27, 2021)

Mark K is correct,

Though one would think that the structural steel erectors, AISC members do steel stairs, one would be mislead, that portion of the building is done normally by a separate fabricator, NOMMA members (National Ornamental and Miscellaneous Metals Association) who work closely with structural fabricators, but are 2 different entities on projects.


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## Rick18071 (Apr 27, 2021)

If the only structural is a outside stairway and no building why wouldn't the frame for it be the PRIMARY STRUCTURAL FRAME. Why would it change if it was in a building?


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## redeyedfly (Apr 27, 2021)

Is everyone ignoring the ICC commentary that explicitly says the stair framing is not required to be FRR?  The commentary is the intent of the writers of the code.


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## Yikes (Apr 27, 2021)

redeyedfly said:


> Is everyone ignoring the ICC commentary that explicitly says the stair framing is not required to be FRR?  The commentary is the intent of the writers of the code.


The code commentary you cited in your post #22 makes a distinction between "stair components" and "structure supporting the stairway".

_Any structure supporting the stairway and the stairway enclosure must be fire-resistance rated consistent with the construction type; however, the stairway components inside the enclosure need only comply with the material limits for the type of construction._

I would say that "stair components" =the items mentioned in IBC 1011.5, which are risers, treads, (incl nosings).  Other people might add "handrails" and "guardrails" and "landings", but to me those are separate from the definition of "stairway".
I would also say that posts and stringers are not stair components, they are the structure that supports the stair components.


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## redeyedfly (Apr 27, 2021)

It's the _inside the enclosure_ part that is key to the code theory.  You're already inside a protected shaft.  There is no reason for additional protection.


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## Yikes (Apr 27, 2021)

redeyedfly said:


> It's the _inside the enclosure_ part that is key to the code theory.  You're already inside a protected shaft.  There is no reason for additional protection.


Sorry, I should have been more specific, I was responding to the second part of Post #1 from RGLA where he was asking about an exterior, unenclosed stair.  Here's what he asked:

_Interior Stairs: Located within an exit enclosure. Steel framing for stairs (consisting of columns, stringers, etc.) is independent of the building frame and does not support the enclosure walls.

*Exterior Stairs: Steel framing for stairs (consisting of columns, stringers, etc.) is independent of the building frame and is exterior of the building envelope (i.e. free-standing with landings connected to building).*

Would you consider one or both of the two conditions part of the "Primary Structural Frame" as defined by the IBC? The definition is not clear in this respect, so I'd though I'd get some opinions._


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## ADAguy (Apr 29, 2021)

Makes for a good discussion, it comes down to the details.


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