Since the dawn of humanity, we’ve used wood primarily for two things: to build structures and start fires. Separately, these attributes are invaluable; together, they have resulted in some of humanity’s deadliest fires. For that reason, model building codes in most countries have traditionally limited the height of wood buildings to fewer than six stories.
Over the last decade, though, attitudes toward taller wood buildings have begun to shift. Recent advancements in engineered wood products, coupled with environmental pressure to build more sustainably, have resulted in the construction of large wood-timber buildings at heights once unimaginable.
The latest example is Brock Commons, an 18-story, 174-foot-tall dormitory tower, currently the world’s tallest wooden-frame building, slated to open in May at the University of British Columbia. A 12-story timber-framed building in Portland, Oregon, isn’t far behind, and neither is a 10-story wooden building in Manhattan. A seven-story wood office building in Minneapolis opened in November.
Brock Commons, a new dormitory at the University of British Columbia, is currently the tallest wooden building in the world at 174 feet. It was constructed in just 70 days once the prefabricated components arrived on site. Photograph: KK law
In Europe and Australia the trend is further along, with numerous tall wooden buildings being built since the early 2000s and many more underway. Projects and designs are getting bolder all the time. An architectural firm has unveiled plans for a 34-story “woodscraper” in Stockholm, while architects in Vancouver have discussed a similar-sized building there. Some architects have even called this moment the beginning of the Timber Age.
While most architects and builders excitedly tout wood’s strength and versatility, as well as its ease of assembly and reduced construction times, critics are concerned that we are just building bigger and bigger tinder boxes.
“I’m in front of building approval committees every month and I’m constantly hearing, ‘this can’t be done,’” said David Barber, a fire protection engineer with Arup who has worked on a number of tall wooden building projects and co-authored the 2013 paper “Fire Safety Challenges of Tall Wooden Buildings” for the Fire Protection Research Foundation (FPRF).
Barber said that a number of proposed tall wooden building projects he’s worked on have been scuttled over fire safety concerns. He contends that, while wooden buildings do behave differently than traditional steel and concrete buildings in a fire, adequate fire safety can be easily achieved.
(Top) The interior of the T3 office building in Minneapolis, which opened in November. (Bottom) THe largest mass timber building in the U.S., it was built using more than 1,100 nail-laminated timber panels, which were assembled in Winnipeg, Manitoba, and shipped to the site. Photograph: Top: Magnusson Klemencic Associates. Bottom: EMA Peter.
Several recent high-profile fires in apartment complexes under construction—built using lightweight engineered wood components—have added to concerns among building officials and the fire service about tall wooden buildings. Barber is quick to point out, however, that taller wooden buildings do not use lightweight engineered wood components, but rather heavier elements such as cross-laminated timber, or CLT, which tests have shown possess greater fire resistance than lightweight materials.
Even so, for some officials tasked with keeping people safe, huge wooden structures are reason for caution regardless of what type of wood is used. “I’m sorry, but I’m very reluctant to endorse anything made out of sawdust and glue,” said former New Jersey fire marshal and firefighter Jack J. Murphy, who is also chairman of the Fire Safety Directors Association of Greater New York and a member of NFPA’s High-Rise Building Safety Advisory Committee. “My mentality is, if we are having a hard time tackling some of these low-rise wood-building fires, how are we going to deal with something taller? They have a lot of selling to do to make us feel comfortable.”
There are several types of heavy timber products on the market now, but CLT is arguably the most popular. A CLT panel consists of three to seven layers of timber boards crisscrossed and bonded together for maximum strength. A typical panel can run 10 feet wide, 60 feet long, and almost two feet thick. The size and thickness of the panels, Barber argues, gives engineered heavy-timber products a natural fire resistance. When the wood burns, it naturally builds up a layer of char on its outer surface, forming an insulated barrier from the heat and fire. By designing the wooden timbers thick enough, “we can engineer the building to naturally resist fire and carry the loads,” Barber said.
In many cases, the wood building’s interior is finished and encapsulated with fire-rated gypsum board, which adds an extra layer of protection. However, it has become an increasingly popular design trend to leave the timbers partially exposed, which makes fire officials like Murphy nervous. “It’s all wood and I think there is a lot of reluctance with that, especially in Manhattan where some of these building footprints are four feet away from neighboring buildings,” he said. “In some of these cases, the outside of the building is wood, and the inside is wood, and so outside-in burns are a concern, especially in a densely populated area.”
Barber admits that the interior wood exposure in tall wooden buildings can increase the fire duration because the wood is adding fuel to itself. “But most buildings of any height are protected with sprinklers, so something would have to go very wrong for the fire risk to increase in any significant way,” he said.
Finding out how much the exposed heavy timber in a residential dwelling impacts fire growth is a key objective of an FPRF project currently underway. “Fire Safety Challenges of Tall Wooden Buildings Phase 2” involves full-scale tests of timber rooms with exposed surfaces with the goal of quantifying how fires in rooms with exposed timber differ in temperature, fire spread, toxicity, and other factors, compared to rooms with timber fully covered in gypsum board. The testing is being conducted this spring and the results should be released this summer.
Barber believes that heavy timber wooden buildings will continue to grow in popularity as officials become more comfortable and familiar with their fire safety and as the public continues to value wood’s advantages as a sustainable resource. It’s not a trend that will subside anytime soon. “As more of these buildings are constructed and people see that this is not as scary as they think, there will be many others,” Barber said. “It’s just a matter of time.”
First responder concerns over tall and skinny buildings
Short on space but brimming with demand, real estate developers in recent years have transformed the neighborhood near the southern end of Manhattan’s Central Park into a steel garden of impossibly skinny, soaring towers. At 1,396 feet and 85 stories, 432 Park, which opened in December 2015, is the tallest residential building in the Western hemisphere, with a footprint of just 94 feet by 94 feet; the total area of about 8,800 square feet is roughly a tenth of that occupied by the shorter Empire State building. Even skinnier, the nearby 82-story tower under construction at 111 West 57th Street will be just 60 feet by 80 feet and more than 1,400 feet tall, with a width-to-height-ratio, also known as an aspect ratio, of 1:23— making it the skinniest building in the world. It will, however, lose its title if a proposed 60-story building, with a footprint of just 50 feet by 54 feet, is built on 37th Street.
Pencil towers have become popular design options for dense urban settings such as New York City. Photograph: Newscom
Jack J. Murphy, a former firefighter, fire marshal, and current chairman of the New York City High-Rise Fire Safety Directors Association, has inspected some of these buildings and says they present unique challenges for firefighters. For one, the buildings’ small footprints mean very narrow scissor stairwells that can have five or more turns between floors. “What would that do to my hose stretch?” Murphy said. The compact size also means tight quarters for operation and medical staging in an emergency.
Meanwhile, in some pencil buildings—a term used for buildings with aspect ratios greater than 1:10—floors housing the buildings’ mechanicals are left entirely open to the exterior to allow the wind to pass through, increasing stability. If a door was left open on these floors during a fire, “the wind could cause the fire to come shooting up there like a blowtorch,” Murphy said. In addition, at least one building he’s inspected had louvers in each apartment to admit air from the outside, which could also affect fire conditions. “This is why it’s critical for fire departments to get out into the field and do recon and intelligence ahead of an event so they know what they’re dealing with,” he said.
Shipping Container Buildings
Living and working in steel boxes
One of the most eye-catching building trends in recent years involves shipping containers, those big steel boxes used to transport goods on ships, trains, and tractor trailers all over the world.
The containers, typically 40-feet long, eight-feet wide, and eight-and-a-half feet tall, have been used as building blocks for everything from tiny off-the-grid escapes to luxurious full-time residences. They have been proposed as emergency relief shelters, as urban skyscrapers to house the poor in the slums of Mumbai, as dormitory housing for universities, and as hotels, restaurants, stores, and everything in between. But are they safe?
Shipping Containers are used in a variety of applications, including residences, emergency housing, and office buildings. Photograph: REA
If done correctly, there is nothing that would prevent a shipping container from being a perfectly safe place to call home, as long as it meets all of the building codes, said Jim Muir, chief building official for Clark County, Washington, and the chair of NFPA’s Building Code Development Committee. From the container proposals he has reviewed, there are a few things to keep in mind, Muir said. First, proper code-compliant doors are required; the latches that come on the container won’t cut it, because they can be locked from the outside. Secondly, proper insulation and windows are needed to comply with the energy code. As is, the containers do a terrible job regulating temperature. In addition, HVAC systems need to be robust to maintain proper ventilation and fresh air intake. Finally, many aspiring container owners are surprised to learn that, even though a typical 40-foot container weighs more than four tons, proper foundations with tie downs are often mandated, especially in earthquake-prone areas.
Porsche Design Tower
Protecting the world's first residential car elevator
Greater Miami has no shortage of luxury condos, but only one allows you to park your Porsche in a “sky garage” 60 stories up in your penthouse.
Earlier this year, residents began moving into the innovative Porsche Design Tower in Sunny Isles Beach, Florida, which features the world’s first residential car elevators. Each of the tower’s three elevators deposit vehicles into private glass garages adjacent to each of the 134 units.
The 60-story Porsche Design Tower in Miami was built around a sophisticated car elevator designed to transport residents' vehicles to their high-rise homes. Photograph: Getty Images; AP/Wide World
For several years, fire protection engineer Michael Sheehan of SLS Consulting has been preoccupied with how to make this new technology safe for residents. Sheehan and his team had to consider every scenario that could go wrong with more than 200 vehicles of various fuel types and associated hazards moving through the building. The biggest challenge was the human element.
“Nobody is ever supposed to run their cars in the garage or in the elevator, but we know someone will at some point,” he said. “The question was, what do we do about it?”
The result is “maybe the safest elevator in the world,” he said, with the entire elevator system having its own custom Underwriters Laboratories listing. Elevator cabs are equipped with numerous air detectors so that even a miniscule amount of carbon monoxide, smoke, flammable gas, or leaking fuel will result in the elevator being recalled to the first floor. Each cab is equipped with a mist suppression system with a refilling water tank on board. The in-unit garages have numerous detection and suppression systems, enhanced exhaust systems, and structural bollards to prevent drivers from accidently gunning their vehicles into the living rooms.
“We had a lot of sleepless nights thinking out different challenges and hazards, but it was one of the most fun projects I’ve ever worked on,” Sheehan said.
As more people choose to live small, code officials combat confusion
Jim Muir has had more than a few people amble into his office with dreams of going tiny.
“We’ve had inquiries, but generally they end up stopping at inquiries when people realize what is and isn’t required,” says Muir, the top building official in Clark County, Washington. “If you build a tiny home you still need to meet the minimum building code. People often don’t really understand there even is such a thing.”
As the tiny home revolution has taken hold in the United States—the industry has spawned books, magazines, and television shows, fueled by people intrigued by the idea of downsizing to save money and simplify their lives—the pint-sized structures have spawned code enforcement confusion.
Tiny home design ranges from modernist boxes to Victorian confections, with a similar range of features and amenities. Photograph: Nicolas Boullosa
Most tiny homes are between 200 and 500 square feet and contain all the standard amenities of a modern dwelling in the space of one or two rooms. Some homes sit on chassis, some on wheels, and others on permanent foundations; some are constructed on site, and others are manufactured elsewhere and transported to the site. With all the variation, some code officials understandably have questions: Are tiny homes manufactured homes? Recreational vehicles? Site-built single-family dwellings? Can a building that small realistically meet the minimum building requirements? Meanwhile, many tiny home enthusiasts ask why their abodes should be subject to building codes at all.
To ease the confusion and identify the code challenges of tiny homes, NFPA’s Building Code Development Committee recently released a white paper, “Building Code Guidelines for Tiny Homes.” The paper addresses stakeholders, including code enforcers, aspiring owners, and community leaders, some of whom are turning to tiny home developments to solve affordable housing crunches.
“Public officials need to keep in mind that these are houses, and that 80 percent of people who die in fires die in residences, so we have to make sure these homes are safe,” says Ray Bizal, NFPA’s senior regional director and former staff liaison to the Building Code Development Committee. “There are people who think they can build a tiny home and not deal with the codes, because for some reason tiny homes are exceptional or different. But if it’s a building, you have to comply with the building code.”
Although tiny homes are not specifically addressed in NFPA 5000, Building Construction and Safety, or in the International Building or Residential Codes, they generally fall under the category of dwellings. The small footprint of tiny homes can make complying with the code tricky, but not impossible.
“Researching the paper, we estimated it takes about 370 square feet to meet all the code requirements,” says Bob Kelly, manager of the Department of Permitting Services in Montgomery County, Maryland, and a member of the NFPA committee that developed the tiny home paper. “There is enough flexibility in the code to make it work—nothing prohibits you from having a sleeping area in a kitchen, for instance.”
While the paper concludes that most code requirements can be met with relative ease, a few typical design concepts do have compliance problems. For instance, to maximize space, most tiny homes use loft space as a bedroom; while building codes do not define loft space directly, there are specific rules for sleeping spaces. Like all habitable space, NFPA 5000 mandates that bedrooms meet a minimum headroom requirement of seven feet, six inches, and be equipped with a primary and secondary means of escape. Most tiny home bedroom lofts meet neither requirement. Also, since the loft bedroom is technically on a second floor, the code requires stairs with a maximum rise and run. Many tiny homes use ladders, not technically allowed.
“You want to be cooperative and look for alternatives, but there are certain things where there isn’t another way,” Muir says. “A basic life safety item like stairs and means of escape—everyone has a reasonable expectation that in an emergency they will be able to get out.” Muir has rejected tiny home plans that he determined did not have proper venting or clearances for wood stoves. Tiny homes should, however, be able to easily meet the code requirement of having automatic home fire sprinklers installed, since almost all have plumbing and running water, the report concluded.
Often, the challenge isn’t the codes, but rather getting homeowners to comply. Many enthusiasts choose the lifestyle to get away from the hassles of government and regulation, according to an angry poster at the website tinyhousetalk.com.
“The last thing tiny house folks want is to be coded and regulated to death,” the commenter wrote. “Falling out of a loft, really? Fire hazards?.... The whole idea of this movement is freedom, I’m sorry to step on toes but you can have accidents anytime, anywhere.”
Some of the staples of tiny home design, such as the ladders that lead to sleeping lofts, do not comply with model building codes. Homes built atop trailer chassis can be categorized as recreational vehicles and are not subject to the provisions of building codes. Photograph: Tomas Quinones (Top); Getty Images
Muir has heard it all before, especially the argument that a person building a tiny house for themselves is assuming the risk and shouldn’t be subject to oversight. “But they have to realize that they may or may not be long-term residents of this house—you have to look at the bigger, longer picture,” Muir says. “Once you’re done with it and sell it to the next person, that next person’s expectation will be that this house meets all the building safety codes, and the authorities having jurisdiction will have that expectation as well.”
Both officials point out that, if done correctly, there is no inherent danger in tiny homes—size is not a disadvantage. “You could argue they’re safer because there’s less distance to travel to get out in case of fire,” Kelly says. “As long as they’re wired properly, installed properly, attached to the foundation, and up to code, they should perform as well as any other home. Where you get in trouble is when you say, ‘Tiny homes are so cute, let’s let them get away with not following safety codes.’”