Interstate Bank Building Fire;
The First Interstate Bank building, the tallest in the
city (and the state of California), is located at the intersection
of Wilshire Boulevard and Hope Street in downtown Los Angeles.
It was built in 1973, one year before a high-rise sprinkler
ordinance went into effect, and had sprinkler protection
only in the basement, garage, and underground pedestrian
tunnel. The 62-story tower measures 124 feet by 184 feet
(22,816 sq. ft.). It contains approximately 17,500 net square
feet of office space per floor, built around a central core.
It is occupied primarily by the headquarters of the bank
corporation with several floors occupied by other tenants.
Approximately 4,000 people work in the building.
The tower contains four main stairways (numbered 5, 5-A,
6, and 6-A in the 12th-floor plan in Appendix A). Stairs
6 and 6-A are enclosed within a common shaft, and stairway
5-A has a pressurized vestibule separating each floor with
the stair shaft. Each stairway contains a combination standpipe
with a pressure reducing valve at each landing. The building
is topped with a helicopter landing pad.
The building has a structural steel frame, protected by
a sprayed-on protective coating, with steel floor pans and
lightweight concrete The exterior curtain walls are glass
A complete automatic sprinkler system costing $3.5 million
was being installed in the building at the time of the fire.
The installation was not required by codes at the time the
owners decided to provide increased fire protection for
the building. The project was approximately 90 percent complete,
with work in progress at the time of the incident. The piping
and sprinkler heads had been installed throughout the five
fire floors and connected to the standpipe supply. However,
a decision had been made to activate the system only on
completion of the entire project, when connections would
be made to the fire alarm systems, so the valves controlling
the sprinklers on completed floors were closed.
Interstatebank Sschematic Floor Plan
The 262 m high, 62-story office tower was the tallest
building built in Los Angeles, USA, in 1973. The tower
was known as the UCB building until 1981, when United
California Bank changed its name to First Interstate
Bank. The tower was renamed 707 Wilshire Tower in
1996 and became Aon Center in 2003.
The tower has a structural steel frame with lightweight
concrete slab on profiled steel deck. A typical floor
measures 37.8 m by 56.1 m, providing about 1,626 m2
of tenant area per floor around a central service
core which contains the lift and staircase shafts.
The external cladding system was made of glass and