REVIEWED BLD2021-0088+BO_Interpretation+5.21.2021_8.15.38_PM+2211574BLD2021-0088
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C) r. IT Building Official Interpretation
Subject: Wood Framed Stairs in Podium Construction
Date: 5/18/2018
RESUB
May 24 2021
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Issue: In mid -rise structures, the building code provides for horizontal separation between
buildings in order to allow for increased area and number of stories of certain occupancy groups
when framed out of wood. This is known as podium style construction, where the wood framed
structure is constructed on top of a non-combustible (type 1A) structure with a 3 hour rated
concrete assembly in between. A common question is whether stairs within an enclosed stairway
may be framed with wood below the level of the podium as they are allowed to be above the
podium.
Determination: It is the determination of the building official that the City of Edmonds will allow
wood framed stairs below the podium level, and hereby recognizes the following proposed code
update as the official interpretation for the relevant IBC sections. This code proposal was
presented earlier this year by the city of Bellevue to the ICC General Committee who voted
unanimously to forward the proposal to the upcoming public hearings that will lead to the
adoption of the 2021 IBC. The proposal has also been submitted to the Washington State
Building Code Council to review for the 2018 IBC.
References: 2015 IBC, ICC Proposal G95-18, Wood Products Council Expert Tips (all attached)
qee4 /
Building Ofifcial V Date
G95-18
IBC: 510.2, 1011.7, 1023.2 (IFC[BE] 1011.7. 1023.2)
Proponent: Lee Kranz, representing City of Bellevue, WA (Ikranz@bellevuewa.gov)
2018 International Building Code
Revise as follows:
510.2 Horizontal building separation allowance. A building shall be considered as separate and distinct
buildings for the purpose of determining area limitations, continuity of fire walls, limitation of number of stories and type
of construction where all of the following conditions are met:
1. The buildings are separated with a horizontal assembly having a fire -resistance rating of not less
than 3 hours. Where vertical offsets are provided as part of a horizontal assembly, the vertical
offset and the structure supporting the vertical offset shall have a fire -resistance rating of not less
than 3 hours.
2. The building below, including the horizontal assembly, is of Type IA construction.
3. Shaft, stairway, ramp and escalator enclosures through the horizontal assembly shall have not less
than a 2-hour fire -resistance rating with opening protectives in accordance with Section 716.
Exception: Where the enclosure walls below the horizontal assembly have not less than a 3-
hour fire -resistance rating with opening protectives in accordance with Section 716, the enclosure
walls extending above the horizontal assembly shall be permitted to have a 1-hour fire -resistance
rating, provided:
1. The building above the horizontal assembly is not required to be of Type I construction;
2. The enclosure connects fewer than four stories; and
3. The enclosure opening protectives above the horizontal assembly have a fire protection
rating of not less than 1 hour.
4. Interior exit stairways located within the Type IA building are permitted to be of combustible
materials where both of the following requirements are met:
4.1. The building above the Type IA building is of Type III, IV, or V construction.
4.2. The stairway located in the Type IA building is enclosed by 3-hour fire -resistance rated
construction with opening protectives in accordance with Section 716.
5. The building or buildings above the horizontal assembly shall be permitted to have multiple Group A
occupancy uses, each with an occupant load of less 300, or Group B, M, R or S occupancies.
=..6. The building below the horizontal assembly shall be protected throughout by an approved automatic
sprinkler system in accordance with Section 903.3.1.1, and shall be permitted to be any occupancy
allowed by this code except Group H.
,6-.7. The maximum building height in feet (mm) shall not exceed the limits set forth in Section 504.3 for
the building having the smaller allowable height as measured from the grade plane.
1011.7 Stairway construction. Stairways shall be built of materials consistent with the types permitted for the type
of construction of the building, .
Exceptions:
1. Wood handrails shall be permitted in all types of construction.
2. Interior exit stairway in accordance with Section 510.2
1023.2 Construction. Enclosures for interior exit stairways and ramps shall be constructed as fire barriers in
accordance with Section 707 or horizontal assemblies constructed in accordance with Section 711, or both. Interior exit
stairway and ramp enclosures shall have a fire -resistance rating of not less than 2 hours where connecting four stories
or more and not less than 1 hour where connecting less than four stories. The number of stories connected by the
interior exit stairways or ramps shall include any basements, but not any mezzanines. Interior exit stairways and ramps
shall have a fire -resistance rating not less than the floor assembly penetrated, but need not exceed 2 hours.
Exceptions:
1. Interior exit stairways and ramps in Group 1-3 occupancies in accordance with the provisions of
Section 408.3.8.
2. Interior exit stairways within an atrium enclosed in accordance with Section 404.6.
3. Interior exit stairway in accordance with Section 510.2.
Reason:
In podium buildings utilizing a 3-hour fire -resistance rated horizontal assembly constructed in accordance with Section
510.2 it is very common for the building above the horizontal assembly to be of combustible construction, including the
landings, stair stringers and treads. The code currently requires that a transition be made from wood to metal, or
some other non-combustible materials, within the stair enclosure at the point where the stair goes from being located
in a combustible building to the Type IA non-combustible building. This is not practical or warranted. Fires do not
typically start within the fire -resistance rated stair enclosure. Exception #4.2 of this proposal provides additional
protection by requiring that the stair shaft be of not less than a 3-hour fire resistance rating with 3-hour rated door
assemblies as required by Section 716. This essentially creates a vertical offset of the 3-hour horizontal assembly
which is currently allowed by Section 510.2. This section states that "Where vertical offsets are provided as part of a
horizontal assembly, the vertical offset and the structure supporting the vertical offset shall have a fire -resistance
rating of not less than 3 hours."
We have also included two 'pointer' exceptions in Chapter 10. Without the pointer exceptions someone might argue
that these Chapter 10 provisions are more restrictive and override the exception in 510.2. The exemption for wood
handrails currently found in the text of Section 1011.7 has been reformatted by placing it into exception #1.
Cost Impact
The code change proposal will decrease the cost of construction .
Allowing stairs to be of combustible construction will be less expensive then if they were required to be of non-
combustible materials. Also, the cost to design the stair will be reduced because a transition from wood to steel (or
other non-combustible materials) will no longer be required.
Internal ID:83
What are the construction material requirements for framing stairs and landings in wood-L. Page 1 of 3
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What are the construction material requirements
for framing stairs and landings in wood -frame
structures? Is a fire resistance -rated assembly
required?
IBC 2015 Section 1011.7 provides this information
on the construction of stairs:
1011.7 Stairway construction.
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.
This indicates that, where the use of combustible
materials is not limited—i.e., Types III and V
Construction —light wood framing can be used to
frame stairs and landings. Heavy timber framing
can be used to frame stairs in Type IV buildings,
which allow heavy timber for all interior framing
including floors. There are no specific fire -
resistance rating requirements for stair and
landing framing. This is corroborated in the code
commentary to Section 1011.7:
/n 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
http://www.woodworks.org/experttip/construction-material-requirements-framing-stairs-1... 11 /21 /2018
What are the construction material requirements for framing stairs and landings in wood-f... Page 2 of 3
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.
In mid -rise structures, the use of the horizontal building provision (commonly called podium or
pedestal style buildings) in IBC 510.2 is common. When the building above the podium is Type
III, IV or V, the portion of the stair shaft and framing above the podium can therefore be framed
in wood. However, a common question is whether or not the stair framing below the podium
may also be framed with wood. To address this, it is useful to look at the provisions of IBC
Section 510.2 (the podium provision):
510.2 Horizontal building separation allowance.
A building shall be considered as separate and distinct buildings for the purpose of determining
area limitations, continuity of fire walls, limitation of number of stories and type of construction
where all of the following conditions are met...
One of the conditions here is that the building below the horizontal assembly is of type IA
Construction. Type IA is required to be framed with non-combustible materials and no
exceptions to this exist in IBC Section 603 that would apply to stair framing and/or floor framing.
Based on these code sections, some Authorities Having Jurisdiction (AHJ) require that the stair
construction below the podium be framed with non-combustible materials. However, a
conversation with the AHJ on this topic is often beneficial as some have acknowledged that
requiring the stair below the podium to be non-combustible while all of the stair framing above
the podium (which is part of the same stair shaft) is combustible would not change the fire
safety of the shaft enclosure. The code commentary to IBC 713.1 notes that "The purpose of
shafts is to confine a fire to the floor of origin and to prevent the fire or the products of the fire
(smoke, heatandhotgases) from spreading to other levels. "The baseline assumption is that
fires start within the main portion of a building rather than within the shaft. This may be seen
as a reason that no fire -resistance rating requirements exist for stairway construction. With this
in mind, some designers have successfully been permitted to utilize wood framing in stair
construction both above and below the podium line in podium style buildings.
http://www.woodworks.org/experttip/construction-material-requirements-framing-stairs-1... 11 /21 /2018