First Interstate Bank, Los Angeles — Five Floors Gutted in the Worst U.S. High-Rise Fire
Summary
The First Interstate Bank tower, a 62-storey, 860-foot steel-framed high-rise in downtown Los Angeles, was gutted across five floors — the 12th through the 16th — by a fire that began on the evening of 4 May 1988, killing one person and injuring roughly forty. The proximate cause was not the ignition, an ordinary electrical fault in an open office floor of furniture and computer workstations, but what the building did with it: a fully developed, post-flashover fire climbed the tower floor to floor through the exterior wall, because its single most important active defense — a sprinkler system — was 90 percent installed and completely inoperative on the night it was needed.
The fire reached temperatures that buckled and sagged the protected steel floor framing, blew out windows, and propagated upward by autoexposure — flame venting from a broken window and re-entering the floor above — aided by the failure of the firestop in the narrow gap between each floor slab edge and the glass curtain wall. No floor collapsed; the building survived as a structure and was repaired, but five floors burned out completely. It is the case forensic engineers cite to show that a modern steel high-rise can be brought to the edge of structural failure not by a flaw in its frame but by the timing of a retrofit.
Completed in 1973 as the tallest building in Los Angeles, the tower had been built and operated legally without sprinklers: the city's 1974 high-rise ordinance applied only to new construction and grandfathered existing buildings. By 1988 the owner was voluntarily installing sprinklers throughout, but on the night of the fire the system was unfinished and dry — contractors had shut the fire pumps down at 22:22 to make connections, and the smoke detectors, repeatedly triggering during the work, had been treated by security as nuisance alarms.
The National Bureau of Standards (now NIST) and the Los Angeles Fire Department both produced engineering post-mortems. Neither found a defective building. They found a defended building with its defense switched off, and a fire-spread path — the curtain-wall perimeter joint — that automatic suppression existed precisely to keep from ever opening. First Interstate became the byword for two lessons at once: that existing high-rises must be sprinklered, not merely new ones, and that a partly installed life-safety system is, for the duration of the work, no system at all.
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Timeline
The Build: A Sprinklerless Tower Built to Code
The First Interstate Bank Building was, on the night it burned, a structurally sound and entirely lawful skyscraper. Completed in 1973 and rising 62 storeys to 860 feet, it was the tallest building in Los Angeles, a steel-framed tower clad in a glass curtain wall, its structural steel insulated to a code-prescribed fire-resistance rating. Unlike the bare-steel towers that collapse outright in a fire, First Interstate never lost a floor.
What it lacked was an automatic sprinkler system, and that too was lawful. Los Angeles adopted its high-rise sprinkler ordinance in 1974, but the requirement reached only new construction; buildings already standing — First Interstate among them, completed the year before — were grandfathered. For fourteen years the tower operated as a fully occupied office high-rise with no automatic suppression on any floor, relying on passive fire-resistance ratings, manual standpipes and an alarm system.
By 1987 the owner had moved to close that gap, and a tower-wide retrofit was roughly 90 percent complete by spring 1988. But "90 percent complete" is, for an active fire-protection system, indistinguishable from "absent": no water-flow alarms were wired, connections were unfinished, and on the night of 4 May the contractors had shut the fire pumps down at 22:22 to work on it. The tower thus entered the most dangerous night of its life in a transitional limbo — neither honestly unsprinklered, with everyone alert to the fact, nor protected. Worse, the smoke detectors had triggered repeatedly during the retrofit, and security had learned to treat their activations as the noise of the work rather than the warning they were.
The Failure: A Fire That Climbed the Outside of the Building
The ignition was unremarkable: an electrical fault, most likely at a computer workstation, in an open office area on the 12th floor around 22:25. In a sprinklered building this is a contained event. Here there were no working sprinklers, the office fuel load did what an unchecked office fire does, the floor flashed over, and the 12th storey became a fully developed compartment fire. It was first reported not by the building's systems but by people on the street calling 911, the internal alarms having relayed nothing; in that window a maintenance employee took a service elevator to the 12th floor and the doors opened onto the fully involved floor, killing him — an elevator delivered to a fire floor being a known killer.
The vertical spread is the heart of the case. A modern high-rise is supposed to be a stack of fire-rated compartments; a fire on one floor should not, by design, become a fire on the floor above. At First Interstate it did, and on the outside of the building. As the 12th-floor fire grew its windows failed — firefighters reported the glazing was thick and hard to break — and flame vented outward, licked up the facade, and broke back in through the windows of the 13th floor: the mechanism engineers call autoexposure, or leapfrogging. Reinforcing it, the "safing" firestop in the narrow gap between each concrete floor slab edge and the glass curtain wall, meant to seal that gap against vertical fire travel, failed, opening an internal path around the floor edges. By these two routes the fire climbed to the 13th, 14th, 15th and finally 16th storeys.
On each burning floor the sustained, post-flashover heat sagged and buckled the protected steel floor framing, deforming it visibly. But the structure held: the frame's fire protection, the building's redundancy, and a hard defensive firefight up the standpipes kept any floor from collapsing. The fire was declared knocked down at 02:19 on 5 May, about three and a half hours after it began, with floors 12 through 16 burned out and roughly 40 people injured.
The Reckoning: A Defended Building With Its Defense Switched Off
The investigations — the National Bureau of Standards' engineering analysis published as NIST IR 89-4061, alongside the LAFD's executive summary and a U.S. Fire Administration technical report — converged on a verdict that was almost the inverse of the usual high-rise indictment. The building had not been cheaply built; its steel was protected and its frame survived. The failure was one of active protection, and of the perimeter detailing that active protection was meant to render moot.
First, suppression was absent at the moment of need. A 90-percent-installed sprinkler system with the fire pumps shut off is, operationally, no system; by the investigators' reasoning the fire that gutted five floors would almost certainly have been held to one had the sprinklers been live. The lesson the NBS and LAFD drew was not "install sprinklers in new buildings," which the 1974 ordinance already required, but install them in existing buildings, and never operate a high-rise in the transitional state where the system is neither off-the-books nor working.
Second, the vertical-spread path was the curtain-wall perimeter. The NBS review explicitly advocated measures against exterior flame spread on curtain-wall facades, better compartmentation, and sealing of the routes by which fire and smoke migrated between floors — a direct naming of the autoexposure-plus-failed-firestop mechanism that turned a one-floor fire into a five-floor one. The building's most modern feature, its glass skin, had become the chimney. The case did not become a story about negligence on the night; it became a structural and regulatory one — a demonstration that the grandfather clause exempting existing high-rises was a standing, citywide liability, and that the joint between slab and curtain wall demands the same rigor as any rated assembly.
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Contributing Factors
Aftermath
The fire killed one person — a maintenance worker delivered to the burning floor by an elevator — injured roughly forty, and gutted floors 12 through 16 of what was then the tallest building in Los Angeles, with sagging, fire-weakened steel framing but no collapse and property loss above $50 million. It is remembered as the most consequential high-rise fire in the city's history and one of the most studied in the United States. Its principal legacy was regulatory: Los Angeles amended its ordinance to require existing high-rises, not merely new ones, to install automatic sprinklers, ending the grandfather exemption that had left the tower defenseless and forcing a wave of retrofits across the city's older towers. The NBS analysis (NIST IR 89-4061), with the LAFD and U.S. Fire Administration reports, made the case a standard reference on three coupled hazards: a transitionally unprotected high-rise, vertical fire spread via autoexposure and failed curtain-wall firestopping, and the operational collapse of alarm credibility during construction. In the literature First Interstate is the byword for a building structurally sound and lawfully built that still lost five floors — because the one system that would have stopped the fire small was switched off, and the perimeter joint that should have sealed each floor was not.
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Lessons
- Never operate an occupied high-rise in the transitional state of a partly installed life-safety system — sequence the retrofit with interim protection, because a 90-percent sprinkler system with the pumps off is zero percent of a defense.
- Sprinkler the existing building stock, not just new construction; a grandfather clause that protects only future towers leaves the occupied ones standing as the hazard the code was written to prevent.
- Treat the curtain-wall perimeter joint as a rated assembly that must actually perform — an uninstalled or failed safing firestop between slab edge and facade connects every floor into one vertical fire path.
- Design and detail against autoexposure: adequate spandrel height, fire-rated glazing or exterior flame-spread control are what keep a vented fire from breaking back in on the floor above.
- Protect alarm credibility and elevator recall: never let routine nuisance activations train staff to ignore detectors, and ensure fire-service control keeps an elevator from ever opening onto the fire floor. ---
References
- Interstate Bank Building Fire, Los Angeles 1988 NIST
- Engineering View of the Fire of May 4, 1988 in the First Interstate Bank Building (NIST IR 89-4061) NIST
- LAFD Executive Summary — First Interstate Bank Building Fire Los Angeles Fire Department
- First Interstate Tower fire Wikipedia
- Interstate Bank Building Fire — Major Fires Investigation Project, Report 022 U.S. Fire Administration / FEMA (TriData)