High Rises: Cost and Building Code Requirements
Our hometown of Columbus has seen a downtown building boom fueled by steady growth in several sectors, including education and health services. According to a recent analysis by the Federal Reserve Bank, several factors are expected to provide even more opportunities for growth: “favorable demographics, including strong population growth, high educational attainment, and a low median age” are among the positive signs that growth in Columbus will continue. Given all this, we often hear questions about why there aren’t more new high-rise buildings being constructed. After all, skyscrapers are what makes up a city’s skyline and, in many places, are instantly recognizable icons that define their cities for generations. There’s not just one answer, of course, but there are some specific implications related to high-rise buildings that shed some light on the challenges of high-rise construction.
What makes a building a high-rise?
Great Pyramid of Giza, photo by Jorge Láscar.
High-rise structures have been around for millennia; think of the Great Pyramid of Giza, which stands 481 feet tall and dates to about 2,560 BC. Egypt is home to several other tall, ancient structures, but is not unique in this regard. Mexico, Iraq, Sri Lanka, Guatemala, Italy, and Belize are also home to structures at least 100 feet tall (approx. 10 stories) that were built before the Common Era – and are still standing!
You may be surprised at what makes modern buildings “high-rise.” It’s not the overall height, not the size, and not the proportions. It’s actually the height between the lowest level of fire vehicle access and the highest occupied floor. Once this distance reaches 75’, the building is considered a high-rise and is subject to specific code requirements that impact its design. These buildings require special consideration, specifically in fire protection and occupant safety. It takes a lot of time to get people out of a really big building. Smoke movement (the stack effect) makes it more difficult, too. Our high-rise buildings are designed to fight fires and keep people safe rather than just to clear everyone out.
What makes 75’ the magic number that triggers the building code requirements? A fire department ladder truck has a 100’ ladder, but the effective reach of an aerial apparatus is only 75’ because, while fighting a fire, the truck will be set back from the building due to obstructions like curbs, landscaping, parked cars, and utility lines.
Building Code Requirements
The International Building Code and the Ohio Building Code have specific sets of requirements regarding high-rise buildings. Generally, this section of the code addresses what the building is made of, how it is made, and what special systems need to be installed.
In addition to the 75’ measure of a high-rise, there are two more important building heights to keep in mind: 120’ and 420’. Once an occupied floor reaches 120’, a fire service access elevator is required. Above 420’ in height, there are many more requirements that must be met. All of these will affect the cost of construction and how space in the building is allocated and used.
Below is a list of current code requirements based on use and occupancy and some brief, simplified information about the implications of these requirements.
This section is based on the 2017 Ohio Building Code and corresponding reference standards; however, these standards can change from time to time. This information is intended to be used for general reference only. Make sure to consult with a design professional for the latest codes and standards for your project.
1. Construction & Type of Construction
Type IA construction allows us to build without limits to height and area but it requires the most amount of fireproofing for the structure and walls. Type IA construction may be reduced to Type IB when a compliant sprinkler system is installed. This reduction allows us to save money on fireproofing, walls, and roofs, though there are some exceptions to this.
2. Shaft Enclosures: Assembly & Materials
Stair, elevator and mechanical shafts are like giant chimneys, and can spread smoke and fire. They require a 2-hour fire resistance rating. Above 420’, the drywall needs to withstand impact loads or the shaft should be built of concrete or block.
3. Fireproofing
Fireproofing products protect steel and concrete structures in the event of a fire, helping to insulate the building’s structure from high temperatures that can cause failure. The bond strength (adhesion) of fireproofing products varies. Normal buildings require 150 psf bond strength; high-rise buildings require 430 psf bond strength; and high-rise buildings over 420’ require 1,000 psf bond strength. The stronger the adhesion, the higher the cost to fireproof the structure.
4. Sprinklers & Alarms
Automatic sprinklers are required in all high-rise buildings. Buildings over 420’ require additional risers for each sprinkler zone. Fire alarms are also required in all high-rise buildings, and facilitate early detection, locating, and communicating. A friendly reminder to check the batteries in your home smoke alarm.
5. Emergency Responder Radios & Fire Command Center Requirements
High-rise buildings are large and complex; the presumption is they will require an emergency responder system. Low-E glass, thick walls, and other equipment all impact radio signals, so this must be a consideration during design. It is crucial that firefighters’ radio devices work reliably throughout the building.
A fire command center must be provided in the building. This is a room dedicated to fire department operations. It must be at least 200 square feet and at least 10’ in the smallest direction. 200 square feet of prime real estate is a lot to “give up” and this cost has to be made up elsewhere in a project. The fire command center must have a minimum one-hour rated fire separation from the rest of the building. The size and location of the fire command center must be approved by the fire chief.
There are 17 specific items required in a fire command center:
Emergency voice/alarm communication system
Fire department communication system
Fire detection and alarm system annunciator
Annunciator unit visually indicating the location of the elevators and whether they are operational
Status indicators and controls for air distribution systems
Fire fighter’s control panel for smoke control systems installed in the building
Controls for unlocking stairway doors simultaneously
Sprinkler valve and waterflow detector display panels
Emergency and standby power status indicators - N/A building has continuous power
Telephone for fire department use with controlled access to the public telephone system
Fire pump status indicators
Schematic building plans indicating the typical floorplan and detailing the building core, means of egress, fire protection systems, fire fighting equipment and fire department access and the location of fire walls, fire barriers, fire partitions, smoke barriers, and smoke partitions
Work table
Generator supervision devices, manual start and transfer features - N/A building has continuous power
Public address system
Elevator fire recall switch in accordance with ASME A17.1
Elevator emergency or standby power selector switch(es) where emergency or standby power is provided - N/A building has continuous power
6. Smoke Removal
The code requires high-rise buildings to have a means of smoke removal, to facilitate post-fire salvage operations. There are 3 ways to comply with this requirement: manually operable windows (40 square feet of windows at intervals of 50 linear feet); mechanical equipment providing one exhaust air change every 15 minutes; or any other approved design.
7. Emergency & Standby Power
An emergency power system that activates within 10 seconds must also be provided. This system provides power for exit signs and lighting, elevator car lighting, emergency voice/alarm communications, automatic fire detection systems, fire alarm systems, and electrically powered fire pumps.
A standby power system that activates within 60 seconds must be provided. This system provides power for the Fire Command Center, ventilation and fire detection equipment for smokeproof enclosures, and elevators.
8. Egress & Evacuation
Fire separation requirements of stairs are increased in high-rise buildings, and all exit stairs are required to be smokeproof enclosures. Buildings taller than 420’ are required to have an extra interior stairway. Stair doors can be locked for security, but need to have the ability to unlock all simultaneously. Additionally, a stairway communications system (e.g. telephone or other two-way system) is required every 5 floors in the stairway, if the stair doors are lockable.
9. Stairs & Elevators
In addition to the requirements listed above for stairs, for buildings above 120’ a fire service access elevator is required. This elevator has to open into a minimum lobby size of 150 square feet, and the lobby has to have a 1-hour fire rating.
All necessary technical information is finalized, and the final set of drawings and specifications will include the information that’s required in order to obtain a building permit from whichever local authority has jurisdiction (eg the city, county, etc.). Your architect will typically handle the permitting process for you, and if the authority has questions, requires additional information, or requests changes/corrections to the drawings (all of these scenarios are pretty common), your architect will take care of it.
The deliverable in this phase is a complete set of drawings and specifications, referred to as the Construction Documents, which will get submitted for permit and given to contractors to develop bids/quotes for the work. Again, an updated cost estimate is usually produced as well.
What is the impact of these code requirements?
Several of the building code requirements mentioned above can have a profound impact on both construction costs and the building’s efficiency. For example, a 200 square foot room on the ground floor is required for a fire command center―but this is prime real estate in a building! A fire service access elevator adds significant cost, and the associated elevator lobby area on each floor takes up space that could otherwise be leasable. A potential additional stair, more sprinkler risers, and more expensive fireproofing are other issues that add cost, take up space, or both. Developers or other building owners must weigh all these requirements when considering how tall to build.
About the author:
Sam Rosenthal, AIA, LEED AP
Sam has provided project management, architectural design, feasibility and planning studies, facilities assessments, document production, and construction administration on various projects since joining Schooley Caldwell. These projects have involved a diverse range of building types, including the historic 47-story LeVeque Tower, the new Michael B. Coleman Government Center for the City of Columbus, and work at the National Historic Landmark Ohio Statehouse. This has given Sam a rare breadth of experience that allows him to work as a knowledgeable and versatile member of any design team. Due to this experience, Sam is able to provide a holistic and contextual approach to design.
