Code analysis

Nadia Kostyshyn, the former plans examiner who taught the students' codes course, comes to the studio in week seven with Danielle Roy, the fire protection engineer. Kostyshyn brings a red pen and a stopwatch. She asks each student to hand her their plans and a one-page code summary, and gives herself five minutes per building, the time she says a plans examiner gives a first reading of a permit application before deciding whether it is ready for review. In five minutes she finds, in Callum's drawings, an open stair that his summary counts as an exit, two exit stairs too narrow for the upper floor's occupant load, a dead-end corridor beyond the east stair, no fire separation around the plant room and no mention of sprinklers. 'None of this is fatal,' she says. 'All of it is normal at this stage. The point of this week is that by Friday it is gone.'

Starting the analysis

Kostyshyn asks the students to follow the twelve sections of the code analysis sheet they prepared in the codes course, in order, because each section depends on the ones before. The first two are quick. The project is a new two-story public building of about 38,900 ft² on a single lot, owned by the city. It is governed by the Minnesota State Building Code, which is based on the 2018 International Building Code with state amendments, and by the city's ordinances; the energy requirements come from the state's commercial energy code, based on ASHRAE 90.1-2019. The state has begun rulemaking to adopt the 2024 codes, but no effective date has been set. The referenced standards include the sprinkler standard NFPA 13, the fire alarm standards and the accessibility standards that the next lesson will apply.

The third section, classification, takes the class an hour. The library, the commons, the multipurpose room and the gathering room are Group A-3, assembly for reading, recreation and gathering. The adult education classrooms are Group B, because education above the twelfth grade is classified as business, and so are the settlement agency's offices. The makerspace is a training workshop, also Group B, with a separation around it because of its dust and machines. Callum chooses to treat A-3 and B as nonseparated occupancies: the whole building must then meet the most restrictive requirements of either, but no rated separation is needed between them. The childminding room raises the hardest question. Kostyshyn explains that a room where children are cared for while their parents attend a class in the same building is not the same as a day care, and the code treats it more leniently; but the class should confirm the treatment with the building official before relying on it, as a real architect would.

Size and construction

The fourth and fifth sections set the size limits and the construction type. Under the IBC, the building's height and area are checked against Tables 504.3, 504.4 and 506.2 for the most restrictive occupancy. Callum proposes Type IV-HT, heavy timber, which allows the timber structure to be exposed if every member meets the code's minimum sizes. Group A-3 in Type IV-HT, with sprinklers throughout, is allowed several times the Commons' area per story and more than its two stories, and the frontage on the avenue and Pell Street would add more if it were needed. Kostyshyn reminds the class that the choice of construction type is not only a code question: it decides which members must be rated or protected, and therefore what the building looks like inside.

Fire separations

The sixth and seventh sections deal with fire separations and spatial separation. Kostyshyn walks the class through the plans one space at a time. The two exit stairs, the elevator shaft and the vertical duct shafts must be enclosed by rated construction: the stairways and shafts by fire barriers with a one-hour rating in a building of fewer than four stories, with three-quarter-hour doors. Callum's concrete cores provide this easily, which is one more reason Szymańska proposed them. The plant room and the electrical room need separations because their equipment is a fire risk. The makerspace needs one because of its dust and machines. The café's kitchen, with a commercial hood, needs its own exhaust system and clearances.

Spatial separation, the limit on openings in walls close to a property line, hardly matters for the Commons, because the avenue and Pell Street are wide and the park is the city's own land. Kostyshyn insists that the students check it anyway and write the result on the sheet. 'The examiner does not know that you looked unless you say so,' she says. The one place it matters is the east wall, which faces Pell Street; the fire separation distance is measured to the center line of the street, which is far enough that the wall may be mostly glass.

The open stair

Callum's open stair in the commons is a wide timber stair with built-in seats, rising from the commons to the library's study floor above. It is the heart of his interior, and he wants to keep it. Kostyshyn explains why it cannot be one of the required exits: an exit must be protected from fire by rated enclosures all the way to the outside, and a stair open to the floors it serves is not. But it can stay, as a stair that people use every day, in addition to the two enclosed exit stairs. The IBC permits an exit access stairway that connects only two stories to be unenclosed, provided it is not one of the required exits. The open stair must still be built like an exit stair in its geometry: uniform risers and treads, handrails on both sides, guards at the open edges. Its built-in seats must not narrow the clear width people use to walk up and down.

Roy adds a point about smoke. An opening between floors lets smoke from a fire on the ground floor rise into the upper floor. In a sprinklered building of two stories the code accepts this, but she asks Callum to keep the opening compact rather than letting it grow into a long slot, and to place it so that people on the upper floor can reach an enclosed exit stair without walking toward the opening. His first scheme has the opening between the classrooms and the west stair; he moves it slightly east, so that the classrooms' path to the west stair runs along the north wall, away from it.

Means of egress

The eighth section is the one that changes Callum's plans most. On the ground floor the building has plenty of exits: the main entrance, the park entrance, the gathering room's door, the multipurpose room's two pairs of doors to the sidewalk and the terrace, and the doors from the two core stairs to the outside. The upper floor is different. Its only exits are the two enclosed stairs, and its occupant load decides how wide they must be. The script below estimates that load in two ways: by the code's occupant load factors, and by the furniture layout Callum has drawn. It then calculates the stair width required for each.

# Upper floor of the Commons: occupant load by the code's factors, then by the furniture layout
spaces = {   # name: (area ft2, code factor ft2 per person, people in the furniture layout)
    "classrooms":         (4500, 20, 180),
    "library study":      (3250, 50, 90),
    "media lab":          (1300, 50, 30),
    "settlement offices": (2400, 150, 20),
    "childminding":       (860, 35, 15),
}
by_factor = sum(a / f for a, f, n in spaces.values())
by_layout = sum(n for a, f, n in spaces.values())
larger = sum(max(a / f, n) for a, f, n in spaces.values())
design = larger                           # the larger of the two in each space
for name, (a, f, n) in spaces.items():
    print(f"{name:<19} by factor {a / f:5.0f}   by layout {n:4d}")
print(f"upper floor: {by_factor:.0f} by the factors, {by_layout} by the layout, design load {design:.0f}")
for label, load in (("factors", by_factor), ("design load", design)):
    need = load * 0.3                     # total stair width required (in)
    each = max(need / 2, 44)              # two exit stairs share it, each at least the minimum
    print(f"{label:<14} total stair width {need:6.0f} in -> each of two stairs {each:5.0f} in")
stairs = [60, 60]                         # Callum's revised stairs (in)
print(f"proposed stairs {stairs} in: total {sum(stairs)} in; one blocked leaves {min(stairs)} in "
      f"= {min(stairs) / (design * 0.3):.0%} of the requirement")

classrooms          by factor   225   by layout  180
library study       by factor    65   by layout   90
media lab           by factor    26   by layout   30
settlement offices  by factor    16   by layout   20
childminding        by factor    25   by layout   15
upper floor: 357 by the factors, 335 by the layout, design load 390
factors        total stair width    107 in -> each of two stairs    53 in
design load    total stair width    117 in -> each of two stairs    58 in
proposed stairs [60, 60] in: total 120 in; one blocked leaves 60 in = 51% of the requirement

By the code's factors the upper floor holds about 357 people, but the furniture layout puts more people in the library study area than the factor for reading rooms does. The code uses the larger number for each space, which gives a design load of about 390. That needs 117 inches of stair width, and Callum's revised stairs of 60 inches each provide 120 inches. If one stair were blocked, the other would provide 51% of the requirement, meeting the code's rule that the loss of any one exit must not reduce the available capacity below half. Their doors at the ground floor discharge directly outside.

The dead-end corridor beyond the east stair is fixed by moving the stair 10 feet east, to the end of the corridor. Travel distances are checked from the farthest point of every room to the nearest exit: the longest, from the far corner of the westernmost classroom to the east stair, is about 125 feet if the west stair were blocked, but the nearest stair is much closer, and the code measures to the nearest exit. Both are well within the 250 feet allowed in a sprinklered building of these occupancies. The multipurpose room, with a posted occupant load of 200 seated at tables, gets two pairs of doors with panic hardware, swinging outward, at opposite ends of the room.

Fire protection systems

The ninth section brings Roy to the front. The Commons will be sprinklered throughout, which the study articles and tables assume and which the city requires in its public buildings anyway. The sprinklers follow NFPA 13: light hazard for the reading areas, classrooms and offices, ordinary hazard for the stacks, the makerspace and the plant room. The sprinkler riser and alarm valve go in a small room on the ground floor beside the west core, with the fire department connection on the avenue wall near the main entrance and within reach of the hydrant. A fire alarm system with smoke detectors in the open areas and the corridors, and with horns and strobes throughout, connects to a monitoring service. The fire alarm panel and an annunciator go at the main entrance, where firefighters will arrive.

Roy makes one request that is not in the code. The exposed timber ceilings, between the glulam beams, form pockets that hold smoke and heat and can delay a sprinkler head's response. She asks Callum to place the sprinkler heads in each pocket rather than on the beam soffits, and to coordinate them with the lights, the acoustic panels and the diffusers so that the ceiling looks deliberate rather than cluttered. 'The best timber ceilings I have seen,' she says, 'are the ones where the architect drew the sprinkler heads.'

Exercise 7: code analysis

• Complete the twelve sections of the code analysis sheet for your building, with references.
• Draw a code plan of each floor showing exits, travel distances, dead ends and fire separations with their ratings.
• Calculate the occupant load and required exit widths with the script, and revise your stairs if needed.
• Locate the sprinkler riser, fire department connection, fire alarm panel and hydrant.

Self-check

• Is every required exit protected all the way to the outside?
• Does every stair, shaft and service room have its rated enclosure?
• Could a plans examiner understand your building in five minutes from your summary sheet?