Stair Framing: Primary Structural Frame or Not?

[RLGA]

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.

 

[steveray]

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....

 

[gbhammer]

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.

 

[brudgers]

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.

 

[gbhammer]

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.

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).

QUOTE]

They have columns, and floors directly connected to those columns, perhaps even bracing members essential to vertical support. Primary structural framing does not mean the shell of the building. A building is a srtucture a structure may not be a building. Primary refers to the part of a structure that resist gravity loads.

A sink and its hanger has none of these things but would provide a nice place for the puke you generate sometimes.

 

[gbhammer]

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.

 

[Codegeek]

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.

 

[imhotep]

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.

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

 

[steveray]

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....

 

[north star]

&

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.

=

 

[brudgers]

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.

 

[Codegeek]

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.

 

[north star]

=



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

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

=

 

[Francis Vineyard]

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

 

[Codegeek]

=

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

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

=

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."

 

[gbhammer]

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

 

[gbhammer]

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

 

[steveray]

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...

 

[Francis Vineyard]

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

 

[TheCommish]

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

 

[JBI]

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.

 

[redeyedfly]

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.

 

[cda]

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.

so they don’t burn???

should not be fire in the stair shaft

 

[redeyedfly]

so they don’t burn???

should not be fire in the stair shaft

FRR and noncombustible are not the same thing.