Appeal 35072

1004.5 Areas without fixed seating

Where approved by the building official, the actual number of occupants for whom each occupied space, floor or building is designed, although less than those determined by calculation, shall be permitted to be used in the determination of the design occupant load.

Appeal requests a modified occupant load based on non-simultaneous occupancy per the exception to OSSC 1004.5.

The total calculated occupant load of the building is 667 occupants, of which the simultaneous E occupant load is calculated at 579 occupants.

The E occupancy rooms of the building are used in two different ways and may be divided into one of two types of spaces, instructional or communal. Refer to the attachment:

1. Red = E occupancy classrooms / instructional areas
2. Blue = E occupancy commons areas
3. Grey areas on the attachment are outside the scope of this appeal as B occupancy or as omissible by the OSSC Chapter 2 definition of floor area, net.

a. Note: Open Area 109 is currently indicated as E occupancy on the submitted permit set. This area will primarily be used by faculty/visitors, and is considered as B occupancy under the appeal and will be updated accordingly on the final permit.

Students at the school will occupy only one of the two types of E spaces in the building at a time – in classrooms receiving instruction, or in the common areas when not being taught. The total calculated occupancy for the instructional spaces is 246. The total for student common spaces is 333.

As the capacity of the school is governed by the number of students it can teach, this appeal requests acceptance of an E occupant load of 246 occupants based on the non-simultaneous occupancy of instructional and common spaces in the building.

Bridges Middle School is a school for children for learning differences. It recently moved into the building at 1250 NW 17th Avenue, displaced by the needs of the Cottonwood School.

The code requires buildings that have undergone a change of occupancy to be reevaluated per the requirements of that occupancy. Portions of the building that were classified as B occupancy under the previous permit have been reclassified to E under the current permit.

When reevaluated against the risk category criteria of OSSC Table 1604.5, the change in occupancy and calculated occupant load increase pushes the building into Risk Category III classification:

1. Buildings and other structures containing Group E or Group I-4 occupancies or combination thereof, with an occupant load greater than 250.

This trigger is only caused by the calculated occupant load of the E occupancy; no other changes to the building meet any of the criteria of Risk Category III.

The calculated occupant load for the E occupancy spaces of the building is 579 occupants, which exceeds the 250 occupant threshold for E occupancy for Risk Category III.

Under daily use, students in the building will only be located in either the instructional spaces or the commons spaces. The school does not have after school events, does not host students
from other schools as with sporting events, and the practical needs of the population limit the acceptable number of visitors to the building. The school does not hold evening or public events, and will obtain event permits in the event that this should become necessary. B occupancy spaces in the building include staff offices or functional spaces (closets, mechanical, etc.) and will not be occupied by students. While the occupant load of the commons areas exceeds that of the instructional spaces, the school cannot accept more students than it’s classroom capacity.

When calculated as occupying either an instructional space or a commons space, the non-simultaneous instructional occupant load for the E occupancy is under the 250 occupant threshold for Risk Category III. Refer to the attachment, which indicates instructional areas in red, and commons areas in blue. The instructional areas total 246 occupants, and the commons areas total 333 occupants. The school cannot accept more students that it has the capacity to
accommodate at once, so the nonsimultaneous occupancy should be limited to 246.

As Bridges Middle School’s students can only be in the learning areas or commons areas but not both at the same time, and the daily building operations will not bring additional students into
the building, it is reasonable to divide the E occupancy spaces into non-simultaneous occupancies, and calculate the student population occupancy accordingly. This non-simultaneous occupant count for instruction is below the threshold requiring seismic reevaluation and upgrade to the building, and meets the intent of seismic risk mitigation of OSSC Table 1604.5. The building otherwise meets or exceeds the life safety requirements of the code.