How do we determine the actual height of a building? Where do we place the dimension line? The history of measuring skyscrapers dates back to 1885, way before AutoCAD or Revit dimensions, when the Home Insurance Building in Chicago was among the first to boast of being the world's tallest building, but the Council on Tall Buildings and Urban Habitat (CTBUH)—or the Joint Committee on Tall Buildings, as it was originally called—wasn’t formed until 1969. Recognized by many as the foremost authority on tall buildings, the CTBUH is often cited in determining the world’s (or country’s or city’s) tallest building. However, the CTBUH is not the only organization with a stake in measuring buildings; the global building information database Emporis is also a major player. Between them, these two organizations provide 10 different ways to determine a skyscraper's height, which we have summarized below.
CTBUH Measurement Methods
CTBUH recognizes three ways to measure a skyscraper, all of which use the level of the finished floor outside the lowest ground level entrance as their baseline.
1. Architectural Top
This is the most common way to measure a building. The architectural top of a building includes any building structure or ornaments, like spires or parapets, but it does not include what the CTBUH considers “functional-technical equipment.” Functional-technical equipment is anything that may be subject to change, such as a flagpole, antennae, or signage. The architectural top method is used to determine the world’s tallest buildings, although due to the subjectivity of what is "architectural" and what is merely "functional-technical equipment," it can sometimes lead to some controversy.
2. Highest Occupiable Floor
To count as the highest occupiable floor, it must be a conditioned space designed for people to legally inhabit it on a regular basis. Mechanical spaces don’t count. This measurement is taken to the floor level.
3. The Tip
The tip of the building is the highest possible point, no matter its material or function. For example, Willis Tower’s architectural top is the roof level at 1,451 feet (442 meters) but its tip measures in at 1,729 feet (527 meters).
Emporis Measurement Methods
In addition to the three methods above, global building information database Emporis defines several other ways to determine a building’s height. In order to easily provide building data, Emporis defines different categories of information through their standards. Some are designed for factual accuracy, whereas others are used to provide estimates when no more accurate data can be found. Still more are designed to provide internal measurements of a building, rather than determining the building's overall height. Emporis also uses a slightly different baseline for many of its measurements: while the CTBUH uses the floor level at the lowest entrance, Emporis uses the lowest point at which the building meets the ground, regardless of its relationship to floor levels.
4. Estimated Architectural
In order to estimate a building’s architectural height, Emporis may calculate the height based on a list of known values. For example, the structure’s approximate height taking into account floor heights of buildings with a similar location and usage.
This is pretty self-explanatory. Emporis' database provides the median distance from floor-to-ceiling. The height of a building may be estimated (very roughly) by calculating the sum of measurements from the top of the floor plate to the ceiling for each level.
Another example in which Emporis provides a median measurement for a building, floor-to-floor height calculates the space between the top of two adjacent floor plates. For estimating total height, floor-to-floor is more accurate than floor-to-ceiling, since it factors in the space in between levels.
7. Main Roof
Buildings with significant roof levels can use this method to measure up to their primary roof plate. This measurement does not include penthouses or turrets.
8. Observation Deck
From the base level to the open-to-air observation deck. An observation deck is defined as the highest exterior viewing space, like the one Meganom designed for a supertall luxury skyscraper in Manhattan.
9. Observation Floor
Unlike the observation deck, the observation floor height is the highest indoor viewing space. Think of the 360-degree observation floor designed for the Expo 2016 Antalya Observation Tower.
The roof height is the highest exterior portion of the buildings shell enclosure. This does not include spires or parapets like the architectural top does, but for buildings with a "main roof," it does include rooftop penthouses or pavilions, unlike the main roof measurement.
There are many ways to define a building's height. But ultimately the method you pick depends on what information you are looking for. The goal should lead you to the right building measurement method.