Appeal 33429

ORIGINAL APPEAL LANGUAGE: OSSC 1028.2 Exit Discharge RECONSIDERATION LANGUAGE (No Change): OSSC 1028.2 Exit Discharge

ORIGINAL APPEAL LANGUAGE:
Exits shall discharge directly to the exterior of the building. The exit discharge shall be at grade or shall provide a direct path of egress travel to grade. The exit discharge shall not reenter a building. The combined use of Exceptions 1 and 2 shall not exceed 50 percent of the number and minimum width or required capacity of the required exits. (Exceptions not included in this text).

RECONSIDERATION TEXT (No Change):
Exits shall discharge directly to the exterior of the building. The exit discharge shall be at grade or shall provide a direct path of egress travel to grade. The exit discharge shall not reenter a building. The combined use of Exceptions 1 and 2 shall not exceed 50 percent of the number and minimum width or required capacity of the required exits. (Exceptions not included in this text).

ORIGINAL APPEAL LANGUAGE:
Exit Discharge from an interior stair to the building’s exterior which is overhung by occupied building area to be protected with enhanced sprinkler protection in lieu of having an exit terminating directly at a public way.

RECONSIDERATION TEXT:
Exit Discharge from an interior stair to the building’s exterior which is overhung by occupied building area to be protected with 1 HR protection to the structure overhead above in lieu of having an exit terminating directly at a public way.

ORIGINAL APPEAL TEXT:
The project is an office building classified as type III-B and is structured as a CLT / Mass Timber building. None of the walls are classified (or operate) as bearing walls. The building is fully sprinklered per NFPA 13.

The building requires 2 stairs and has two stairs. The north stair exits through the lobby and complies with OSSC 1028.2 on Exit Discharge, Exception 1. The south stair, (which is the subject of this appeal) exits directly to the exterior but is overhung by two occupied building stories where the structure (inherent in the III-B construction type) is unrated and the exit distance under the building to the public way, which we will term the “exterior travel path” has a length of 46 FT. This document proposes enhanced sprinkler protection at the “exterior travel path” between the egress door from the stairs and the path to the public way.

The enhanced sprinkler protection at the area of the “exterior travel path” is proposed as follows. The Fire Sprinkler Hazard Classification of the building area, if not for this appeal, would prescriptively be classified Light Hazard (Light is the first level of five levels of such classification). This appeal proposes a sprinkler design in this travel path as one that meets Ordinary Hazard, Group 1 requirements (Ordinary Hazard, Group 1 is the second of the five levels of this classification system). This zone of increased fire sprinkler hazard rating is proposed to extend from the south wall of the overhung area to the building’s drip line further south (approximately 12’-2” away) while aligning with the stair enclosure’s west wall and continuing to the public way at the east side of this area. The specific sprinkler design of this area will be provided as a separate permit package; it is not included in the prime permit submission.

Refer to appeal exhibit exhibits as follows: APP-2A is a site plan which locates the stairs, exit, and area of additional sprinklering; APP-2B is a building section showing the relationship of the overhanging building to the proposed travel path with additional sprinklering; APP-2C show the south façade of the impacted area as a 3D graphic.

Context regarding exterior wall construction and stair shaft ratings are as follows. The wall construction and floor construction at the area of the building’s south façade is NOT required to be rated in accordance with OSSC 705 Exterior Walls or per the general requirements of the construction type per OSSC table 601. The stair shaft that is the subject of this appeal meets 2 HR requirements; note while OSSC prescribes that his stair be only 1HR, the stair is required to meet 2 HR requirements per the Fire Department’s Alternate to Aerial Fire Apparatus Roads provisions.

With this proposed configuration, there is a co-benefit of providing enhanced protection for occupants exiting south from level 1 through the main corridor path which will have an enhanced protection along the travel distance of 32 FT where their travel converges with the “exterior travel path”.

RECONSIDERATION TEXT:
The project is an office building classified as type III-B and is structured as a CLT / Mass Timber building. None of the walls are classified (or operate) as bearing walls. The building is fully sprinklered per NFPA 13.

The building requires 2 stairs and has two stairs. The north stair exits through the lobby and complies with OSSC 1028.2 on Exit Discharge, Exception 1 (note that this north exit is the subject of a different code appeal due the presence of the vestibule along the exit path).

The south stair, (which is the subject of this appeal) exits directly to the exterior but is overhung by two occupied building stories, which we will call “the back porch area”. This building exit has a travel path through the back porch area with a length of 46 FT to the public way; here the code prescriptively requires that the exit from the stair door directly exit to the public way. Neither the construction type (III-B) nor other code provisions require this back porch area to have a fire rating. This appeal proposes 1 HR of protection to the structure above in lieu of directly exiting to a surrounding public way. Of note, the structural protection proposed covers the entire back porch area and not just the ceiling area along the exit travel path or otherwise proximal to the south stair.

The 1 HR protection to the structure will be provided through calculated fire resistance (in accordance with OSSC Section 722 CALCULATED FIRE RESISTANCE). Note, both tables 722.6.2(1) on TIME ASSIGNED TO WALL BOARD MEMBRANES for wood assemblies and 722.7.1(1) on PROTECTION REQUIRED FROM NONCOMBUSTIBLE COVERING MATERIAL for mass timber assemblies, provide the value of 40 minutes for 5/8” type ‘X’ gypsum sheathing. This appeal proposes (2) layers of 5/8” type ‘X’ gypsum board to be fastened to the mass timber assembly above; such a construction will have an assembly that exceeds 60 minutes, providing a 1 HR assembly.

Refer to appeal exhibit exhibits as follows:
>APP-2A is a site plan which locates the stairs, exit, and area of additional structural protection.
>APP-2B is a building section showing the relationship of the overhanging building to the proposed travel path with structural protection.
>APP-2C shows the south façade of the impacted area as a 3D graphic.
>APP-2D is a section detail (located in APP-2B) depicting the installation of the structural protection in this area.

Context regarding exterior wall construction and stair shaft ratings are as follows. The wall construction and floor construction at the area of the building’s south façade is NOT required to be rated in accordance with OSSC 705 Exterior Walls or per the general requirements of the construction type per OSSC table 601. The stair shaft that is the subject of this appeal meets 1 HR requirements per OSSC 1023.2 (since it connects only 3 levels). [Note in the original appeal, this stair was noted to require 2 HR protection].

With this proposed configuration, there is a co-benefit of providing enhanced protection for occupants exiting south from level 1 through the main corridor path which will have an enhanced protection along the travel distance of 32 FT where their travel converges with the “exterior travel path”.

ORIGINAL APPEAL TEXT:
The architectural configuration of the proposed design provides a “covered back porch” or “loggia area” (to use the term of classical architectural design) between the parking lot and building’s back door along its south side. This covered back porch feature provides protection from the rain (during the wet months) or shade (during the dry months) as one enters the building as well as allowing occupants to enjoy being outside even when the outside might not otherwise be considered comfortable. The fact that the south stair is set-back from the outermost face of the exterior of the building is what allows the back porch feature to exist.

While the “exterior travel path” from the stairs to the exterior could be made through structural protection (by increasing the use of gypsum board and fire rated glass and frames in this area) it would cost more and require the need for specialty openings which might not be replaced in-kind by future owners of the building. As such, an increase in the classification of the sprinkler system in a localized area is a more straightforward approach and is a method often approved in lieu of structural protection. The additional sprinkler protection will increase safety compared to the approach or increasing fire ratings since it would result in a greater capacity to extinguish a fire where providing structural protection would only provide greater capacity to withstand a fire. Note that the back porch area is open on 3-sides and this will further mitigate any smoke dissipation that may occur that is not otherwise addressed by the additional sprinkler capacity provided as a part of the proposed design.

Architect has discussed this appeal with Life Safety Plans Examiner, Renay Radtke Butts.

RECONSIDERATION TEXT:

The architectural configuration of the proposed design provides a “covered back porch” or “loggia area” (to use the term of classical architectural design) between the parking lot and building’s back door along its south side. This covered back porch feature provides protection from the rain (during the wet months) or shade (during the dry months) as one enters the building as well as allowing occupants to enjoy being outside even when the outside might not otherwise be considered comfortable. The fact that the south stair is set-back from the outermost face of the exterior of the building is what allows the back porch feature to exist.

The exterior travel path from the stairs to the public way, is short, only 46 FT in length. Providing 1 HR structural protection above the travel path from the south stair as well as the rest of the back porch area, would provide protection to those using the stair, similar to the protection required by the continuation of the stair or the addition of an exit passageway. Additional considerations related to the safety inherent in the configuration include: A) the greater potential for smoke dissipation along exterior travel path than in an enclosed configuration since the travel path is open on 3-sides, and B) the flexibility to those egressing to choose an alternative path without needing to pass through a door to the parking lot to escape the impacts of an alarmed event.

Architect has discussed this appeal with Life Safety Plans Examiner, Renay Radtke Butts.

ORIGINAL APPEAL LANGUAGE OSSC 602.3 Type III, RECONSIDERATION TEXT: City of Portland Building Code Guide, Topic Type III Construction - OSSC/6/#4

ORIGINAL APPEAL TEXT:

Type III construction is that type of construction in which the exterior walls are of noncombustible materials and the interior building elements are of any material permitted by this code. Fire-retardant-treated (FRT) wood framing and sheathing complying with Section 2303.2 shall be permitted within exterior wall assemblies of a 2-hour rating or less.

RECONSIDERATION TEXT:
In lieu of using fire-retardant-treated wood framing, the Bureau of Development Services (BDS) will allow non-fire-retardant-treated wood framing within exterior walls of R-2 occupancy buildings of Type III construction without a building code appeal provided that the conditions set for the Code Guide are met.

ORIGINAL APPEAL LANGUAGE

This appeal proposes the use of non-fire-resistant treated wood (Non FRT) in the exterior walls in conjunction with 5” thick mineral wool (aka rock wool) insulation friction fit between the 2x6 nominal untreated standard wood stud framing to fill the entire wall cavity of Type III construction.

RECONSIDERATION TEXT:
For an office building without bearing wall (a lower hazard than an R-2 Occupancy) we would like to
consider the use of mineral wool insulation in place of FRT exterior wall framing in Type III construction as
an alternate for the following Code Guide Requirements:
> Sacrificial studs (condition 4, condition 17)
> All exterior wall coverings to be non-combustible material (in only prescribed limited capacity, condition 5)
> Fire department access for this building being subject to Fire Department Approval and not this Code Guide (Condition 11)
> All stairs to have roof access (one of two stairs proposed, condition 12)
> That the extents of firestopping at exterior walls be limited to rated walls only rather than all (condition 13).

ORIGINAL APPEAL TEXT:

The proposed wall assemblies in attached EJ include metal siding or reSAWN (or equivalent) wood exterior cladding, siding support system, a weather barrier, one (1) layer 5/8" type X exterior gypsum sheathing, 2x6 wood studs 16” on center (OC), 5.5” thick mineral wool (aka rock wool) insulation friction fit between the 2x6 nominal untreated standard wood stud framing to fill the entire wall cavity, a vapor barrier, and one (1) layer 5/8" type X interior gypsum wallboard.

The proposed wall Details X611, X612, and X614 (Figures 4-1 – 4-3 in attached EJ) are compared to UL Design No. U305, while the wall Detail X613 (Figure 4-4 in attached EJ) is a double wall and compared to UL Design No. U341.

The BUF building is fully sprinklered per NFPA 13 with a fire separation distance greater than ten (10) feet, therefore the proposed non-load bearing exterior wall assemblies are required to be rated from the interior only and meet a 1-houre fire resistive rating per 2022 OSSC Table 705.5 and Section 705.5. The locations of exterior walls are illustrated by red dashed line along the exterior of the building in Figure 4-5 in attached EJ.

RECONSIDERATION TEXT:

The following details the conditions listed in the Code Guide followed by justification of applicability, where the requirement is either addressed, not applicable, or an alternative method is proposed.

(1) Exterior bearing walls shall be protected based on their fire separation distance.
This condition does not apply to this appeal – This condition addresses exterior bearing walls, and this project does not include any exterior bearing walls.

(2) Exterior non-bearing walls shall be protected on the inside and outside with at least one layer of 5/8” minimum fire-rated gypsum board or gypsum sheathing.
This condition has been met – The building is fully sprinkled per NFPA 13 with a fire separation distance greater than 10 feet. The proposed non-load bearing exterior wall assemblies are rated from the interior only and meet a 1-hour fire-resistive rating per 2022 OSSC Table 705.5 and Section 705.5. The proposed assembly includes one (1) layer 5/8" type X exterior gypsum sheathing and one (1) layer 5/8" type X interior gypsum wallboard. Additional protection is provided by a vapor barrier and 5.5” thick mineral wool (rock wool) insulation friction fit between the 2”x6” nominal untreated standard wood stud framing to fill the entire wall cavity, equivalent to UL Design No. U305 and U341.

(3) Non-fire-retardant-treated wood framing within exterior walls must be enclosed by gypsum board or gypsum sheathing, except where specifically noted in this Guide.
This condition has been met – All non-fire-retardant framing at exterior walls meets this requirement on the interior and exterior faces of the walls: The 2”x6” nominal untreated standard wood stud framing within the exterior wall assembly is enclosed by gypsum board or gypsum sheathing, as prescribed by this condition. The inclusion of mineral wool insulation in conjunction with non-fire-retardant-treated wood framing as proposed will provide equal or greater protection than fire-retardant-treated wood.

(4) All openings in exterior walls for doors, windows or wall-mounted HVAC units and louvers must be protected with a sacrificial stud at the sides and top of the opening. The sacrificial stud may not be used to support a structural vertical load.
This condition does not apply – Based on the fire separation distance for the north and south exterior walls of the building a rating is not required, and therefore a sacrificial stud is not of concern to prevent the ingress of fire into the membrane of the exterior wall assembly. Although the fire separation distance on the east and west sides require a 1-hour fire resistance rating, the mineral wool installed in the wall assembly should prevent the spread of fire within the wall membrane.

(5) All exterior wall coverings shall be of non-combustible material.
This condition is subject to this appeal – The exterior wall assemblies include combustible elements, while the Code Guide specifies that none of the exterior wall coverings should include wood siding. The combustible materials present include metal siding or reSAWN (or equivalent) wood exterior cladding. This reSAWN product has a flame spread rating of greater than 25 feet and has been addressed within the appeal. It is proposed that the enhanced fire resistance and minimal quantity of the applied material be offset by the enhanced wall assembly performance, refer to submitted Engineer Judgment regarding justification.

(6) Combustible roof sheathing and framing shall be protected from exposure to fire from above with gypsum-based products, fire-retardant-treated wood sheathing or similar UL-tested products installed above or below the roofing membrane and/or rigid insulation.
This condition has been met – Roof insulation is covered with a gypsum-based cover board (1/2” Dens Deck Prime as Basis of Design) and is therefore protected from exposure to fire from above.

(7) Selective smoke detection coverage shall be installed in the Type III portion of the building per NFPA 72, National Fire Alarm Code, beginning at the access point to the path of egress and continuing until reaching all exits. If the exit passes through a lobby or other intervening space, selective smoke detection coverage requirements shall be extended to such spaces until reaching the exit discharge.
This condition has been met – Based on the occupancy of this building, smoke detection is not required or provided except for the elevator lobbies and machine rooms. Required smoke detection coverage will be provided, and fire alarm scope will be submitted to the City as a Deferred Submittal.

(8) At least one operable exterior window shall be provided in each dwelling unit with a minimum opening width of 3-1/2 inches.
This condition does not apply – The condition for one operable exterior window in each dwelling unit does not apply to the proposed office building.

(9) Walls and floor assemblies separating dwelling units shall have tested fire-resistance ratings of not less than 1 hour.
This condition does not apply – Dwelling units do not apply to the proposed office building; therefore, the requirement for 1-hour separation of dwelling units does not apply.

(10) The base allowable building area specified in the OSSC for R occupancies in Types III-A and III-B construction shall not exceed 12,000 square feet. Area increases in accordance with the OSSC are allowed.
This condition does not apply – The most conservative occupancy proposed for the new building (A-2) allows a base occupancy of 28,500 square feet. The maximum building area per story is 9,737 square feet, which is smaller than the 12,000 square feet allowed by this Guide condition.

(11) The distance from the top of the roof parapet to the lowest required fire apparatus setup point, as determined by the Fire Marshal’s Office, shall not exceed 75 feet. A minimum of one dominant street-facing building façade shall meet Fire Code requirements for fire apparatus aerial access.
This condition has been met – The building height is less than 75 ft as required (the building is 43 ft). Access provided for Fire Department Access has been approved by the Fire Marshall.

(12) All required egress stairs shall include access to the roof. Such access may be via any roof access method listed in OSSC Chapter 10.
This condition is subject to this appeal – Two (2) stairs serve this building but only has one provided method of roof access. Stair 2 roof access is provided via a roof hatch and ship’s ladder per 1011.12. The building is three (3) stories with its roof structure at 38’-6” above Level 1. It is proposed that the need for two points of roof access be mitigated since the overall area and footprint of the building is less than its allowable maximum (the Code Guide allows for a building of 6 stories). Additionally, the walls for the stair shafts are less than 27 ft apart, so multiple points of roof access would not provide enhanced roof area access.

(13) All penetrations through the exterior wall covering shall be fire-stopped at the exterior sheathing. “Penetrations” for purposes of this Guide includes elements such as conduits and piping and does not include “openings” such as doors, windows or wall-mounted HVAC units and louvers.
This condition is subject to this appeal – Per 2022 OSSC Section 718.2, fire blocking shall be installed to cut off concealed draft openings and shall form an effective barrier between floors. Firestopping will be installed in all penetrates in rated walls. Firestopping will not be provided in non-rated walls, interior and exterior; none of the exterior walls are bearing walls.

(14) Ducts and vents penetrating exterior walls shall be 26 gage minimum.
This condition has been met – Duct and vents penetrating exterior walls shall be 26 gauge minimum as stipulated by the Code Guide.

(15) No unprotected penetrations are permitted through the underside of fire-rated exterior wall projections that are required to be rated, including cornices, eaves, bays, exterior balconies, and similar projections extending beyond the exterior wall.

This condition has been met – All penetrations in fire-rated assemblies will be equipped with firestopping assemblies. The project does not include wall protection described in this condition: cornices, eaves, bays, exterior balconies, or similar projects extending beyond the exterior wall.

(16) Elevator hoistways opening directly into corridors shall be pressurized or have smoke-tight protection as required for doors opening into fire-resistive corridors.
This condition does not apply – The office building has a height of 43 feet and does not require pressurized elevator hoistways. Additionally, buildings with A-2 and B occupancies do not require corridors to be fire rated when fully sprinklered per OSSC Chapter 10.

(17) Framing at walls, floors, ceilings, and roofs must be constructed as specified in the graphic detail drawings numbered 0 - 19 contained in this Guide, unless greater fire resistance is provided. Conditions not covered in this Guide must be constructed in accordance with the OSSC.
This condition is subject to this appeal – While Code Guide OSSC/6/#4 allows the use of non-fire retardant-treated wood framing within exterior walls of R-2 occupancy buildings of Type III construction, this appeal proposes the use of non-fire-resistant treated wood in conjunction with mineral wool in a B occupancy. The Guide does not include any requirement for mineral wool to be used in conjunction with non-fire retardant-treated wood framing. The proposed exterior wall assemblies have been analyzed in the attached EJ in comparison with UL-listed assemblies and concluded to meet or exceed the required 1-hour fire-resistance rating.

ORIGINAL APPEAL TEXT:

The attached EJ provides the fire analysis that supports the use of mineral wool (aka Rock Wool) insulation in the wall cavity of untreated wood stud framing as an alternative to FRT wood stud framing permitted by the OSSC section 602.3. The analysis is based on published temperature data from full scale testing of multiple configurations of fire rated stud walls. The assemblies tested included 1 hour and 2 hour rated assemblies, with and without insulation, insulations included fiberglass and Rock wool types.

The proposed exterior wall assemblies Details X611, X612, and X614 have been reviewed and were compared to the tested UL Design No. U305, while X613 was compared to the tested UL Design No. U341. The proposed assemblies with the combination of one (1) layer 5/8” gypsum wallboard, mineral wool friction fit into the wall cavity, wood studs, and fireblocking provide equal or greater than protection to a wall assembly that includes traditional FRT wood studs.

As outlined in the attached EJ, this analysis concludes the proposed exterior wall assemblies will meet or exceed the required 1-hour fire-resistance rating required by the 2022 OSSC Section 602.3 and OSSC Table 705.5.

RECONSIDERATION TEXT:

Propose alternate means than those suggested in the Code Guide, as this building is an office building with B Occupancy, and the Code Guide primarily refers to an R-2 Residential Occupancy. The following section details where conditions in the code guide are met, where they are not applicable for this building, and where an alternate solution is being requested.

The BDS Code Guide OSSC/6/#4 will allow non-fire retardant-treated wood framing within exterior walls of R-2 occupancy buildings of Type III construction without a building code appeal. The key differences between the purpose of the Guide and the conditions of the proposed design include Group B versus R-2 occupancy as well as the inclusion of mineral wool in conjunction with non-fire retardant-treated wood framing, in lieu of alternative protection provided by the Guide including sacrificial studs. Refer to the Proposed Design.

Additionally, as discussed in ICC commentary, the Group R occupancies represent some of the highest fire safety risks, while the risks in the Group B occupancy are relatively low. While many of the additional protection requirements of the Guide are provided in the project design, some are not provided, while others are inapplicable to the business occupancy. Based on the strength of the Engineering Judgment report and the additional protection afforded by the mineral wool, we request approval of this appeal.

Architect has discussed this appeal with Life Safety Plans Examiner, Renay Radtke Butts.

OSSC 1028.2 Exit Discharge; Exception 1.1

Discharge of interior exit stairways and ramps shall be provided with a free and unobstructed path of travel to an exterior exit door and such exit is readily visible and identifiable from the point of termination of the enclosure.

Modification requested is to allow occupants exiting from an interior exit stair to pass through a vestibule (with direct exit access) in lieu of requiring that the exit door is entered directly from the lobby connected to the stair.

The project is an office building classified as type III-B and is structured as a CLT / Mass Timber building. The building is fully sprinklered per NFPA 13.

The building requires two (2) stairs and has two (2) stairs. The stair that is subject of this appeal is following with path of OSSC 1028.2 on Exit Discharge, Exception 1. The interior stair used for exit discharge exits through a lobby. There is a glazed vestibule on the lobby proposed to be used for both entry and exiting. The vestibule mitigates weather intrusion of weather into the lobby. While the vestibule does not prescriptively comply with OSSC’ s 1028.2, exception 1.1 since a vestibule may be considered an obstruction, this vestibule is less than 30 FT in travel distance away from the stair and is glazed. From the point where the interior exit stairway exits into the lobby, the door to the vestibule is visible and readily identifiable as is the door that exits to the exterior.

Refer to exhibits labeled APP-4A and APP-4B which respectively show the plan of this area and a view from the interior exit stair.

The 2021 Oregon Efficiency Specialty Code (OECC), based upon ASHRAE Standard 90.1-2019 includes a provision requiring vestibules at building entrances in its provision 5.4.3.3; this provision conflicts with the OSSC 1028.2 exception 1.1 which requires that exits from interior stairways have free and unobstructed path of travel to an exit door. The requested modification is to reconcile this code conflict by allowing for the exit path from an interior stair used for exit discharge to pass through a vestibule.

This solution provides for the energy conservation inherent in having a vestibule while including equivalent safety related to exiting. The short distance, less than 30 FT, from the interior exit stair through a glazed vestibule provides occupants a readily visible and identifiable path to the exit consistent with the intent of the code (OSSC 1028.2 Exit Discharge; Exception 1.1). In addition to this short path to the vestibule, this general area of the building is highly glazed such that occupants will easily observe the city sidewalk area directly surrounding the building which will reinforce that a path through the vestibule will lead to the exterior out of the highly public entry to the building.

Architect has discussed this appeal with Life Safety Plans Examiner, Renay Radtke Butts.