Modern design and construction techniques have relaxed many of the constraints that form the basis for 21st-century office building design. Low-rise, mid-rise, and high-rise office buildings serve a variety of end users and each requires individual analysis. However, certain universal guidelines exist that organize the building infrastructure and reinforce the perception of rational planning and flexibility. Lenders, developers, and corporate design managers strongly endorse several time-tested and generally accepted truths—the seven pillars of office building design.
Granite Park III in Plano, Texas.
1. Choosing the right floor plate size to meet the needs of tenants in the submarket being served. Floor plate sizes vary by market segment and should be tailored to accommodate large tenants, average-size tenants, and desirable minimum-size tenants. Rentable space of 25,000 to 28,000 square feet (2,300 to 2,600 sq m) per floor plate is considered average for office buildings. The core-to-glass dimension is critical. Forty-two feet (12.8 m) from the core to glass is desirable for tenants using primarily private offices. Forty-seven feet (14.3 m) from the core to glass is more desirable for users who incorporate significant open workstation areas in their layouts. There are exceptions to every rule, but the guidelines are generally scalable: for example, corporate campuses are often low-rise structures that honor these principles by linking multiple floor plates like boxcars, resulting in rentable space on floors of 50,000 to 75,000 to 100,000 square feet (4,600 to 7,000 to 9,300 sq m).
2. The five-foot-by-five-foot (1.5-m-by-1.5-m) planning grid. This grid, when superimposed on the entire floor plate for office buildings, regardless of class or status, is perceived to optimize space planning efficiency. This convention does not necessarily inhibit free thinking about the shape or massing of an office tower, but core and shell designers must carefully consider the impact on the ability to plan space and demonstrate adherence to performance standards when deviating from orthogonal geometry. Standardized glass sizes are inseparably coupled with the planning grid discussion. Building maintenance and operations personnel must purchase attic stock for each unique glass light size. Therefore, while the perimeter wall may deviate from the grid, glass sizes and mullion spacing should track the five-foot module whenever possible.
3. A central location for the core, with the elevator lobby ideally positioned at the midpoint of the core. Larger tenants want direct elevator lobby exposure for their entrances. When several tenants share a corridor, it is important that they share access to the elevators, restrooms, and the service elevator equally. Ideally, exit stairs should be located within the center core, but the locations are subject to the building code requirements for minimum separation. To minimize the common area corridor, attention should be given to the shape of the building or the floor plate size. Either of these can dictate if one or more of the stairs should be disconnected from the central core. There are exceptions to every rule that may warrant a side-core or end-core location, but generally the center core office floor plate is most efficient and readily adaptable to changes desired by tenants.
4. The 30-foot- (9.1-m-) wide structural bay. Private offices are predominantly ten feet or 15 feet (3 or 4.6 m) wide. Corporations tend to group private offices on the perimeter. While sometimes a column grid 25, 35, or 40 feet (7.6, 11, or 12 m) wide may satisfy a particular user’s needs, lenders will discount the value of buildings that deviate from the 30-foot bay because they make buildings harder to sell. While the use of perimeter columns is unavoidable, they can and should be shaped and properly oriented to minimize disruption of tenant planning.
5. Column-free interior spaces. Advances in structural engineering technology have contributed to increased span lengths from the exterior wall to the interior side of the building core walls, leaving tenant layouts unencumbered. In the case of floor plates of 25,000 to 28,000 square feet (2,300 to 2,600 sq m), no more than four interior columns are located outside the core area. Preferences on structural framing vary by city and region. For example, in north Texas, a 21-inch- (53-cm-) deep concrete frame using post-tensioned, wide-pan joist and post-tensioned girders is dominant. Consideration for construction logistics related to “flying” the concrete table forms can significantly reduce the cycle time for forming, placing, and finishing elevated concrete floor slabs.
One Victory Park in Dallas, Texas.
6. Overhead HVAC distribution as the standard for speculative office buildings (now challenged). Recent advances in under-floor heating, ventilating, and air conditioning (HVAC) technology have begun to challenge this pillar of design in corporate office build-to-suits, though lingering questions about broad market acceptance have to be recognized. There are many reasons to continue developing under-floor HVAC systems, including:
- reduced floor-to-floor height;
- individualized air volume controls;
- reduced energy consumption and operating costs;
- better indoor air quality;
- greater flexibility for moves and changes;
- reduced labor cost for power, telephone, and data cable installation; and
- enhanced flexibility for architectural floor treatments.
Some traditions are slow to change, and there is a great deal of resistance to change in this arena among tenants, building owners, brokers, and many interior architects. Some users object to what they perceive to be a hollow sound for the floor inherent in inferior raised-flooring systems. Floor air diffusers play an important role in user comfort, but they may compromise a monolithic floor treatment. Developers may fear that savings associated with reduced floor-to-floor heights, such as on exterior skin cost, or elimination of conventional ductwork may not be sufficient to offset the upfront cost of the raised floor system. Multitenant floors create significant construction challenges because it may be necessary to complete the entire raised-floor plenum in order to occupy a partial floor area.
Perhaps the burgeoning appetite for sustainable design will contribute to further development and application of under-floor air systems.
7. Sustainability. As of this year, pursuit of environmentally conscious principles such as carbon neutrality by the federal government and the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) certification program has permeated the entire office market. Most office buildings currently being designed are precertified under the LEED program and are being planned in accordance with its green building criteria.
The goal of reducing the impact of new construction on the environment is becoming a reality. With the LEED certification initiative for existing building operations and maintenance (EBOM), it is conceivable that the movement will continue to grow. Green power sources are becoming mainstream and the notion of acquiring carbon credits is gaining momentum. Recent advances in electric automobile design and growing acceptance of alternative methods of producing electricity will dramatically reduce the carbon footprint of commuters. Reducing the heat-island effect in urban areas through green roof designs coupled with high-performance building materials and further refined mechanical, electrical, and plumbing systems will reduce consumption of fossil fuel and accelerate movement along the path toward sustainable communities.
While office building design continues to evolve in response to technological advances, many conventional construction methods and principles are changing at a slower pace. These seven pillars are rooted in the past, but form the basis for reliable outcomes in future office building design