Civil Engineering Magazine THE MAGAZINE OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS

Downtown Los Angeles Ditches its Flat Roofs

By T.R. Witcher

New fire safety regulations may remove helipads from skyscrapers, opening the door to more creative architecture that could transform the city's skyline.

 

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The Wilshire Grand, designed by Los Angeles-based A C Martin Partners, may be the first skyscraper in Los Angeles to pierce the city’s formerly flat skyline when it is completed next year. But thanks to regulatory changes, it is not likely to be the last. A C Martin

 

January 20, 2015—Downtown Los Angeles (DTLA, as it is known locally) used to be Skid Row, an empty and unattractive dead zone known mostly for its large homeless population. But in recent years, thanks to projects as varied as the Staples Center sports arena and the Disney Concert Hall, DTLA has reemerged as the center of this sprawling metropolis. Downtown is now home to more than 50,000 residents.

It appears that only downtown's boxy and bland skyline is standing in the way of completing the transformation. The flat-topped skyline view of the city from famed Mulholland Drive is rather depressing, notes Bruce Miller, the president of the local land-use consulting firm Bruce A. Miller and Associates. "In the future you'll be able to look out and see a world-class city, which we are—comparable to Chicago, New York, and lots of other places."

That future may now be closer at hand, courtesy of a change in regulations, announced last fall, that no longer requires Los Angeles skyscrapers to come equipped with helipads, which tend to lead to flat, graceless buildings. Proponents hope the regulation reform will usher in a new era of spire-topped, elegant high rises. The change, Miller says, "is wonderful for the city."

According to information from the mayor's office, the revision to Regulation No. 10 affects buildings in different height ranges, starting at 75 ft and going up to 1,000 ft. For the tallest category, between 420 and 1,000 ft, helipads can be eliminated if the buildings include a fire-service access elevator or an exit stair "in addition to the required elevators and stairs; two stairways with roof access; enclosed elevator lobbies; and power-operated automatic shutters for escalator openings or stairways separate from the egress (exit) system."

Automatic sprinkler systems will also be required throughout the whole building, as will video-camera surveillance of fire-service access elevator lobbies and every fifth-floor landing in the exit stairways. Additionally, egress stairways will be required to carry a specific capacity of people in the event of an emergency.

Regulation 10 was created in 1974, during an era when tall buildings had fewer fire safety protections. Andew Thul, P.E., the director of West Coast operations and the senior fire protection engineer for Cosentini Associates (a Tetra Tech company that has an office in Los Angeles), was part of a working group that consulted on the regulation change. He says that at that time, few tall buildings were provided with automatic sprinklers, and active smoke-control systems were a new requirement. Since then, many—though not all—have been retrofitted with automatic sprinklers. "Removal of helipads had been something that the majority of fire-protection engineers in the L.A. area had been advocating for a number of years," Thul says. "Given the history of high-rise building fires in the U.S. and the relative risk associated with loss of life during high-rise fire events, the utility of helipads is pretty minimal."

To date in Los Angeles there has been only one rescue from such a helipad—in 1988, when police helicopters rescued five people from the roof of the 62-story Aon Center (then the First Interstate Bank Building).

A few years ago the city formed a working group to examine the notion of changing the regulation. The group consisted of 20 people, including fire protection engineers, architects, developers, current and former fire department officials, helicopter pilots, and a few attorneys. Thul says that the group was formed as a practical way to evaluate an issue that has been under discussion for years. "People have been talking about flat buildings in L.A. since probably the late 1990s."

As Thul notes, rooftops generally aren't the location to which people should be headed in a burning building anyway. "The primary goal is always down," he points out. "If you can't go down in a high-rise building, the secondary option is to shelter in place because of the level of safety and redundant systems in high-rises."

Thul adds that high-rise buildings in Los Angeles feature compartmentation, a form of fire-resistance rated construction, as well as active smoke-control systems that "provide a substantial level of safety for building occupants who cannot egress."

"We did interview the firefighters, and frankly they do not like landing on a building that's on fire," says Arpy Hatzikian, a principal of the global architecture firm Gensler who was also a member of the working group. In addition, she says that new helicopters are too heavy for the older helipads.

The California building code is based on standards established by the International Code Council, which itself has taken recommendations from the 9/11 Commission Reportand the International Council on Tall Buildings, implementing changes in the code to increase safety for firefighters and evacuating occupants.

As fire chief Ralph Tarrazas explained in a letter to the L.A. City Council, decades of technological improvements—as well as 20 significant building-code changes related to life safety through the years—have made the old rules "look extremely outdated."

He continued, "These high-rise building enhancements will be used on a much more frequent basis than the rarely used helipad."

Modern building codes have substantially increased the level of safety for building occupants and first responders, Thul notes.  "The City of Los Angeles code now requires redundant city supply mains for fire sprinklers in all high-rises over 120 feet in height, redundant sprinkler risers for buildings over 420 feet, and redundant fire pumps for all buildings over 200 feet," he explains. "This, combined with requirements for smoke control in buildings more than 75 feet in height, voice/alarm communication fire-alarm systems, enclosed elevator lobbies, smoke-proof exit enclosures, and fire-service access elevators result in buildings which are substantially more robust than those designed and constructed in 1970."

High-rise buildings designed under current City of Los Angeles codes include either active or passive floor-by-floor smoke control and pressurized stairs. Active smoke-control systems rely on a pressure differential across a smoke barrier, such as a wall or a floor. That pressure differential, Thul notes, overcomes the buoyancy effect of smoke, and keeps smoke from migrating throughout the building. Passive smoke control, on the other hand, functions by ensuring tight construction and low leakage rate across barriers to contain the smoke to a single area or floor.  He adds that when these systems are designed well, "both methodologies are very effective in controlling the spread of fire and products of combustion such as smoke and hot gases."

For buildings taller than 1,000 ft, Thul says, the approach to fire-protection and life-safety building compliance changes, and is more dependent on a cohesive overall performance-based approach. "You're dealing with a whole different animal," he says.

Some buildings may use a phased approach that relies on either stairs or occupant-evacuation elevators. Others may be built around sheltering in place until firefighters arrive. In a tall and wide building such as, for example, Burj Khalifa, the strategy might be to evacuates part of the building and shelter in place in another.

Still, not everyone is happy with the change. In an October op-ed piece in the Los Angeles Times , Los Angeles Fire Department (LAFD) assistant chief Patrick Butler disagreed with the decision to do away with the helipads. "Current protocols require helicopters to respond to all reported high-rise fires with a crew of firefighters on board," Butler wrote, noting that the LAFD's aviation unit is one of the best in the country. "And rooftop access via helicopter can enable firefighters to get more quickly to top floors during skyscraper fires. The faster that firefighters can get to where a fire is burning in a high-rise, the faster they can control and contain it, stopping it from spreading through the building and saving lives. Relying on internal elevators or on climbing hundreds of flights of stairs is certainly one option, but why limit our abilities?"

Additionally, he notes that the department began conducting evacuation drills—including aerial evacuation drills—after the terrorist attacks of September 11, 2001. "The drills demonstrated that the city's fleet of helicopters could evacuate as many as 300 people an hour," Butler wrote. "This could help in terrorism situations or when an active shooter is loose in a building."

Still, the working group members believe fire safety will not be compromised by the change. Assuming other requirements are met, developers will have the option of removing helipads, replacing them with smaller "touchdown" areas, or leaving them in place.

"We don't have a skyline in Los Angeles because of this," says Hatzikian. "Every roof is flat. So now designers-architects—are going to have the option to entertain having a spire for a more attractive skyline with the design, or having an occupied observation deck on top of their building in lieu of the helipad. That's real estate that's sitting there, not collecting rent."

"What it's going to do is open up the opportunity for interesting design in downtown that hasn't been there in the past," Thul adds. He estimates there are 13 or 14 high-rises that would likely take advantage of this over the next five years. "It could radically change the shape of downtown," he says.

Architect Mike Rich, AIA, the owner of Los Angeles-based Large Architecture, just finished a new residential tower in DTLA that includes a helipad. When asked if the new code would have changed the building form, he says, "It would have. It would have meant that we didn't have to build the helipad on top of the building [and that] we didn't have to get FAA [Federal Aviation Authority] approval. It would have saved the project a little bit of money."

Helipads, which are usually about 50 by 50 ft, can be problematic for designers because of their close proximity to rooftop mechanical systems. Like the others, Rich thinks the new regulation will free designers to shape more creative rooftops. Under the old regulation, "You don't have as much flexibility to do what you want in the shaping of the building," he notes.

Hatzikian says the new regulation will continue to evolve over time. So, does this mean that Los Angeles designers will be scrambling to dust off those old spire-filled plans that they've had to stick in the bottom of their drawers? "If it's going to make it exciting, interesting—why not?" she says. "It's time for L.A. to have a skyline."

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