BOMA Webinar: Seattle Building Code – Calculating the Occupant Load of Office Spaces

Presenter Bios and Contact Info

Ardel Jala, PE is Building Official for Seattle Department of Construction & Inspections. She is responsible for establishing technical policy and consistent enforcement of Seattle Building Codes throughout the department. Prior to joining the city in 2011, she worked as a structural engineer for 15 years designing seismic upgrades for a variety of existing building and historic preservation projects. Ardel serves on the Structural Engineers Association of Washington Existing Building Committee, the AIA Seattle Technical Code Committee and the BOMA Technical Code Committee. Ardel enjoys time with family, eating, being prep cook for her husband’s cooking and planning the next family adventure. She serves on the PTSA Racial Equity Committee for her children’s school and volunteers weekly for Food is Love, a local non-profit established during Covid19 that delivers meals from local restaurants to food insecure families. Email: ardel.jala@seattle.gov

Amie Joyce, IIDA, LEED ID + C, is a Project Manager and Senior Interior Designer with Weaver Architects in Seattle. She is responsible for all phases of project work starting with initial client contact, programming, planning, design development, construction documentation, and construction administration. Project types include tenant improvement, building re-positioning and common area upgrades, as well as working directly with owners and managers to implement BOMA surveys and strategies, as well as feasibility planning of vacant spaces for marketing purposes. Prior to moving to Seattle and starting work with Weaver Architects in 2009, Amie spent 11 years in Southern Arizona working in tenant improvement design and custom cabinetry. Email: AmieJ@weaverarch.com

Richard Pellinger Technical Codes Manager, City of Seattle Richard is currently the Technical Codes Manager for Seattle Department of Construction and Inspections. He is responsible for implementing technical policy and the Seattle Building Codes throughout the department. Prior to joining the City in 2007, Richard worked in Seattle with over 20 years of experience in building design and construction, including residential, mixed-use, and commercial work. Richard serves on the AIA Codes Committee and is a voting member for the ICC Code Development. In addition, he is a proud graduate of North Dakota State University. Email: Richard.Pellinger@seattle.gov

Cited Resources Find your building occupancy: https://buildingconnections.seattle.gov/2021/02/03/how-to-find-your-business-occupancy/

Reopening resources for Businesses: https://www.seattle.gov/mayor/covid-19/covid-19-reopening

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BOMA: Calculating the Occupant Load of Office Spaces

Ardel Jala and Richard Pellinger

Photo by John Skelton

May 12, 2021

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Agenda

SDCI:

✓ Assembly vs Office Areas✓ Concentrated business use areas (new in 2018 SBC)✓ Non-simultaneous occupancy for the purpose of determining egress, plumbing fixtures or

risk category designation.✓ Code compliant options to increase existing egress capacity

Weaver Architects:

✓ Design and treatment of smaller tenant suites.✓ Egress design and review of multi-suite office floors and full floor tenant improvements✓ What does post-pandemic return to work look like?

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Typical assembly occupancies

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Typical open office seating

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What is an Assembly Occupancy?

Group A Occupancy - AssemblySeattle Building Code (SBC) 303.1: “...for the gathering of persons for purposes such as civic, social or religious functions; recreation, food or drink consumption or awaiting transportation.”

Many types including:• Sporting Event Facilities• Food/drink consumption• Large gathering spaces such as

▪ Conference rooms▪ Lecture halls

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Occupancy - Small Assemblies

Small buildings and tenant spaces – SBC 303.1.1

• Less than 50 occupants → Group B occupancy

Small assembly spaces accessory to another occupancy – SBC 303.1.2

• Two exceptions (<50 occ, <750 sf)

• Group B occupancy OR part of the occupancy it is accessory to

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What if my Assembly meets Ch 5 Accessory limits?

Accessory Occupancies

SBC 508.2: “...ancillary to the main occupancy of the building or portion thereof.”

• Occupancy classified by Ch 3.

• Still an Assembly occupancy when exceeds limits of SBC 303.1.2 Small Assembly spaces

• Area limited to 10% of floor

• Height and location in the building per the main occupancy of the building

• No separation to main occupancy

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Occupancy Classification vs Occupant load factor

• Occupancy classification per SBC Chapter 3• Occupant load factor per SBC Chapter 10

assigned based on how a space is used

Conference Room example: Occupancy is based on size and occupant load

Assembly (A-3) OccupancyOffice (B) Occupancy

Occupant Load Factor is the same for these conference rooms → 15 net sf/occ assembly without fixed seats, unconcentrated

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New in 2018 SBC: Office Occupant Load Factor = 150 gross sf/occ

▪ Office Occupant Load per 2018 SBC Table 1004.5 changed to

150 gross sf/occ

▪ Previously was 130 gross sf/occ for sprinkled building; 100 gross for non-sprinkled

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Potential impacts of an Assembly occupancy classification or assembly occupant load factor

• Adding occupants to a floor can trigger an increase in required egress capacity and may require another exit from the story

Assembly occupancies have higher structural live load requirements (100 psf) than typical office floors (50 psf). May require strengthening existing floor framing.

Assembly occupancies are not permitted as part of a blanket permit

Adding occupants to a floor can trigger more plumbing fixtures

Changing a floor to all assembly occupancies can trigger sprinklers or fire alarm requirements for buildings without those systems (not as typical)

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Separation of adjacent spaces

1) The vertical plane between the spaces is 50% or more

2) There is a major egress path separating adjacent spaces.

POLICY: Where multiple seating areas are adjacent to one another, each room is considered a separate space for determining occupancy classification when:

50% vertical plane

Major egress

Open office

Open office

Lounge Kitchen

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Calculating Occupant Loads - Assembly or Office?

Whether a space should be assigned an assembly occupant load factor (OLF) or an office occupant load factor will depend on how the space is used and configured

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Occupant Load and Non-simultaneous use

SBC Ch 10 Means of egress sizing is based on the occupant load with all spaces fully loaded. SDCI does not accept non-simultaneous use as justification to reduce the occupant load for calculating required egress capacity. Occupancy lives with the building not with the tenant and we cannot regulate use of the space.

SBC Ch 29 permits limited non-simultaneous use. Spaces “not normally occupied” and ancillary to the main occupancy of the building can be assigned zero occupants for calculating min plumbing fixtures.

Non-Simultaneous Use: same people in a conference room or on the balcony as on the floor so should not have to double count those occupants

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Assembly or Office OLF? Small Conf Rooms

SDCI POLICY: SDCI accepts an office OLF (150 sf/occ gross) for small conference rooms <=150 sf

Small conference rooms, huddle rooms, focus rooms, breakout rooms <=150 sf→ Office OLF

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Assembly or Office OLF? Reception Area

Reception Areas

seating areas with adjacent assembly spaces → Assembly OLF

PantryPrivate booths

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Assembly or Office OLF? Reception Area

Reception Areas

Example: Adjacent to assembly space but limited area given circulation path to elevators and conference rooms

→ Office OLF

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Gathering space adjacent to assembly spacesi.e. break rooms, large conference rooms, large gathering areas

→ Assembly OLF

Assembly or Office OLF? Lounge seating

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Assembly or Office OLF? Lounge Seating

Lounges, Collab Space

Lounge areas withinopen office seating

→ Office OLF

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Assembly or Office OLF? Kitchens

• Cafeteria, Kitchenette, coffee counter, break room, beverage bar → Assembly OLF

• OK to omit built in casework from OL calculation

• Does SDCI accept non-simultaneous use for these spaces? No

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Assembly or Office OLF?

Office or Concentrated business use OLF

Assembly OLF

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• Balconies → Assembly OLF

• OK to omit major egress path and permanent planters when applying a net occupant load factor for assembly

• Does SDCI accept non-simultaneous use for these spaces? No

• Structural: live load is 1.5 times LL of area served, not to exceed 100 psf

Assembly or Office OLF? Balconies

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Occupant Load Factor: Office Example

150 gross

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Occupant Load Factor: Office Example

Small Conf Rooms <150 sf- Ok at Office OLF

150 gross

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Occupant Load Factors for other typical spaces

• Circulation on the floor – it depends

• Where adjacent areas are primarily open office with an OLF of 150 gross sf/occ → apply the same OLF to circulation

• Where adjacent areas are primarily assembly with an OLF using a 15 or 7 net sf/occ → OK to exclude assignment of OLF to circulation

• Main lobby spaces at primary entrance

• Generally have large open areas with no programming

• Assign something to lobby – OK to use an office OLF

• Assign seating areas assembly OLF

• Training spaces - 20 net sf/occ Classroom OLF ok if configured like a classroom; else use 15 net sf/occ for Assembly

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Occupant Load Factor: Office Example

OLF at CIRCULATION - It depends!

150 gross

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New in 2018 SBC: Concentrated Business Use

Apply a concentrated business use OLF when the ratio of the number of occupants per square feet based on the seating layout is closer to 1:50 than 1:150

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Clustered Conference Rooms

• Contiguous conference rooms assigned an assembly occupant load factor but may be individually classified as Group B occupancy

• When grouped together as a cluster, likely to be used simultaneously

• POLICY: Design for an assembly live load (non reducible) when the contiguous assembly areas covers a significant portion of floor plate - more than 25% of the floor area of the story

SDCI Code Interpretation “Clustered Conference Rooms – Live Load and Occupancy”

http://www.seattle.gov/Documents/Departments/SDCI/Codes/2015SBC16072ClusteredConfRooms.pdf

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Seismic Risk Category and non-simultaneous use

• When a buildings occupant load reaches 5,000 occupants it triggers in increase from a typical Risk Category II building to Risk Category III.

• The building must be designed for the higher force seismic forces and snow loads associated with the higher RCIII.

• Non-simultaneous use is accepted for calculating occupant loads for determining Risk Category. See SDCI Code Interpretation “Risk Category Occupant Load Calculations”

http://www.seattle.gov/Documents/Departments/SDCI/Codes/2015SBC16045RiskCategoryOccupantLoad.pdf

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New in 2018 SBC: who reviews plumbing?

Public Health – Seattle King County (PH-SKC) still has authority for plumbing permits…

New in the 2018 SBC• SDCI to check SBC Ch 29 including the count and

location of minimum plumbing fixtures• PH-SKC is enforcing fixture count as shown on

construction permit plans as approved by SDCI

2015 SBC … going back to 2003 SBC and earlier..• PH-SKC review and enforced Ch 29

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SBC Ch29 Plan Review - Min plumbing fixtures

When is plan review of minimum plumbing fixtures required for a tenant improvement in an existing building?

• Change of occupancy classification or change of use for an existing tenant space or building.

• An addition or alteration that increases the occupant load of an existing building

• Addition or alteration that proposes a reduction in plumbing fixtures/facilities

What permit do I need for alterations to plumbing fixtures?

• SDCI permit (STFI or plan review depends on extent of alterations)

• PH-SKC plumbing permit

What if my proposed alterations do not impact the toilet facilities, are not part of a change of use and do not increase the occupant load on the story?

Existing facilities may remain as existing non-conforming without complying with current plumbing fixture requirements.

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What options are there to increase my egress capacity?

What options are there when the proposed occupant load of a floor exceeds the egress capacity of the existing two stairs?

• Sprinklers and an emergency voice/alarm communication system

• Horizontal Exit• Refine occupant load analysis• Egress modeling (Code modification)

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Horizontal Exits – flexibility around SBC 1006.3

Horizontal Exits can be always be used to increase existing egress capacity, i.e. from 440 to 500 occ.

SBC 1006.3 prohibits horizontal exits to count towards the required number of exits from a story. However, SDCI is open to a code modification to waive this when:

• The building is Type 1 construction

• The building is sprinklered throughout (NFPA13)

• Other two exits must meet exit separation requirements

• Movable partitions OK only within allowable openings of the fire barrier

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QUESTIONS?

Ardel Jala, Building OfficialArdel.jala@seattle.gov206-684-0573

Richard Pellinger, Technical Codes ManagerRichard.Pellinger@seattle.gov

DW

COPY /SUPPLY

BREAK

SERVER

ENTRY

RECEPTION

COLLABORATION

5' BENCHING

LARGECONFERENCE

MED. CONF.

SM. CONF.

OFFICE OFFICE

LARGECONFERENCE

ENTRYHOTEL COPY

8x8WORKSTATIONS

5x7WORKSTATIONS

OFFICE

SERVER

CAFE

COPY /COFFEE MEETING

Conf / Collab. > 150 sf (1/15 Net SF)Lounges

Business Office Areas (1/150 Net SF)

Unplanned Vacant Tenant Space -Occupant Load Max 77

Concen. Business Use (1/50 Gross SF)

Conf / Collab. < 150 sf (1/150 GrossSF)

Break Rooms w/ Seating (1/15 Net SF)

MEETING

MEETING MEETING

Suite Area Appx 4,970 SF

Maximum Available OccupantLoad = 77

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11

13

16LOUNGE

37

1

11

10

1 1

19

24

12

1

4

12

Suite Area Appx 1,380 SF17 Occupants

Suite Area Appx 3,470 SF57 Occupants

Suite Area Appx 4,940 SF115 Occupants

Multi-Tenant Floor Non-Sprinkled Bldg.

Per SDCI, Concentrated Business Useis intended to be utilized in areas thathave a much denser headcount that atypical office setting.

If the Concentrated Business Use areais not "significant portion" of the tenantspace, after Assembly areas havebeen deducted from the SF, they canbe tabulated at the Business OfficeAreas factor of 1/150

"Significant Portion" = 30% or more ofthe available SF dedicated to thedenser layout.

Egress Components that Determine Occupant Load in this Example:Egress Stair Door (Qty of 2): 34" clear opening / .2 x 2 = 340 OccupantsStair Width (Qty of 2): 41.5" wide / 0.3 x 2 = 276 Occupants276 Occupants is the maximum load that the stairs can support

Area of Concentrated Business Use is a "significantportion" (i.e. more than 30%) of available area

Area of Concentrated BusinessUse is a "significant portion" (i.e.more than 30%) of available area

Note: Buildings and space layouts shown in slides are not to scale and arenot indicative of specific buildings or tenants. Cores and buildingperimeters have been altered for presentation purposes. All areas calledout do not reference BOMA calculations for Usable or Rentable area.

DW

5' BENCHING

LARGECONFERENCE

COLLAB

COFFEESERVER

PRINT RECEPTIONMEET

PHONE

PHONE

PHONE

PHONE

OFFICE OFFICE

CAFE

COLLAB

CO

PY

/ SU

PP

LIE

S

6x8WORKSTATIONS

6x8WORKSTATIONS

Why is this not consideredConcentrated Business Use?

This area consists of 25% of theavailable tenant suite SF afterAssembly Areas have beendeducted Conf / Collab. > 150 sf (1/15 Net SF)

Lounges

Business Office Areas (1/150 Gross SF)

Conf / Collab. < 150 sf (1/150 Gross SF)

Break Rooms w/ Seating (1/15 Net SF)

21 24

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Suite Area Appx 4,970 SF74 Occupants

For this example, if the Prospective Tenant desiredto install 5' Benching in both Open Office Areas,that area would total 60% of the available tenantsuite SF after Assembly Areas have beendeducted, requiring them to be calculated asConcentrated Business Use.

With the conversion to Concentrated Business UseArea and the associated denser calculation of1/50, the total Suite Occupant Load would increaseto 126 Occupants, which is 49 occupants too highto be supported by the egress componentsavailably on the floor.

POTENTIAL TENANT SPACE LAYOUT LIMITED TOA MAXIMUM OCCUPANT LOAD OF 77 OR LESS

Strategies for Limiting Occupant Loads toAccommodate Egress Components

- Limit Conference Rooms > 150sf- Limit Break Room Spaces- Increased Built-out Environment

- Consider Traditional 6x8 or larger workstations to work within the 1/150 calculation

- Limit amount of Dense Bench Seating in Open Office so as not to trigger the Concentrated Business Use Classification

Multi-Tenant Floor Non-Sprinkled Bldg.Note: Buildings and space layouts shown in slides are not to scale and arenot indicative of specific buildings or tenants. Cores and buildingperimeters have been altered for presentation purposes. All areas calledout do not reference BOMA calculations for Usable or Rentable area.

COLLAB

KITCHEN

SEATING

SEATING

GAMES

OFFICEOFFICEOFFICE

OFFICE

OFFICE

OFFICE

OFFICE

COLLAB

CO

PY

/ SU

PP

LIE

S

CONFERENCE

COFFEE

OFFICE OFFICE OFFICE OFFICE

SERVER

MEETING

CONFERENCECONFERENCE

CO

FFEE

FLEXIBLEMEETING

PHONE

PHONE

OFFICE

OFFICE

OFFICE

OFFICE

PHONE

PHONE

CONFERENCE

STO

RA

GE

CO

ATS

CO

PY

/ SU

PP

LIE

S

STO

RA

GE

CO

ATS

WELLNESS

CONFERENCE

PHONEOFFICE

PHONEOFFICE OFFICEOFFICEOFFICE OFFICE

PANTRYSTORAGE

COLLAB

MEETING

5' BENCHING

5' BENCHING

5' BENCHING

5' BENCHING

5' BENCHING

5' BENCHING5' BENCHING

STORAGE COATS

RECEPTION

Full Floor Tenant Sprinkled Bldg.

Conf / Collab. > 150 sf (1/15 Net SF)Lounges

Business Office Areas (1/150 Net SF)

Concen. Business Use (1/50 Gross SF)

Conf / Collab. < 150 sf (1/150 GrossSF)

Break Rooms w/ Seating (1/15 Net SF)

Per SDCI, Concentrated Business Useis intended to be utilized in areas thathave a much denser headcount that atypical office setting.

If the Concentrated Business Use areais not "significant portion" of the tenantspace, after Assembly areas havebeen deducted from the SF, they canbe tabulated at the Business OfficeAreas factor of 1/150

"Significant Portion" = 30% or more ofthe available SF dedicated to thedenser layout.

Egress Components that Determine Occupant Load inthis Example:Egress Stair Door (Qty of 2): 34" clear opening / .15 x 2= 453 OccupantsStair Width (Qty of 2): 44" wide / 0.2 x 2 = 440Occupants

440 Occupants is the maximum load that the stairs cansupport

(Note: Max Occupant Load Decreases to 293 ifSprinklers & Fire Alarm are not updated to 2018 SBC)

EGRESS PATH

COLLAB

COLLAB

COLLAB

56 58

13133613

12

1

1

25

393818

20

19

Individual areas are separated bymin. 50% wall or barrier, which doesnot trigger a Change of Use forAssembly Occupancy

3

3

3

64

Suite Area Appx 21,730 SF435 Occupants

Note: Buildings and space layouts shown in slides are not to scale and arenot indicative of specific buildings or tenants. Cores and buildingperimeters have been altered for presentation purposes. All areas calledout do not reference BOMA calculations for Usable or Rentable area.

Area of Concentrated Business Use is a"significant portion" (i.e. more than 30%)of available area. This plan examplereflects a 40% SF usage for ConcentratedBusiness Use