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From 2015 to 2017, UrbanToronto and its sister publication, SkyriseCities, ran an occasional series of articles under the heading Explainer. Each one took a concept from Urban Planning, Architecture, Construction, or other topics that often wind up in our publications, and presented an in depth look at it. It's time to revisit (and update where necessary) those articles for readers who are unfamiliar with them. While you may already know what some of these terms mean, others may be new to you. We will be (re)publishing Explainer on a weekly basis.
Along with the updated and republished articles, we are also adding to the Explainer series, filling in gaps in the general knowledge bank. This week's article is an overhaul of an earlier one.
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Determining a building's official height can be a tricky process. We recently explained the different building height classifications, ranging from low-rise to supertalls, but today we'll explain how those measurements are determined in the first place. At UrbanToronto.ca, we use the Council for Tall Buildings and Urban Habitat (CTBUH)'s Height Criteria to ensure the consistency of the information displayed in our Database, and to avoid any confusion amongst our readers. The CTBUH recognizes three different ways to measure a tower, as explained and illustrated below through the case of One World Trade Center in New York City.
The first and most widely used height measurement technique involves measuring a building from its lowest, open-air, pedestrian and/or most significant access, to its architectural top. The architectural top of a building includes spires, but excludes all other functional-technical features such as antennas, signage, flagpoles, or lightning rods, as shown in the picture below. In other terms, this definition does not include equipment that may be removed or changed, or that was added later.
In Toronto, the planning department typically cares about the height from established ground level to where the last major step-back occurs, even if there may be a portion of a mechanical penthouse, or elevator overrun, or parapet wall that rises above the bulk of the roof area. For our purposes, the highest permanent part of the structure is what we measure to, so that may be the roof of a mechanical penthouse, or or an elevator overrun, or the top of a parapet wall running around a roof (if one is included in the plans.) For this reason, the height stated on UrbanToronto may differ from a lower total height quoted in documents written for planning department purposes. In the case of the documents that quote the step-back height, they are mostly concerned with how far shadows are cast.
The second way to measure the height of an edifice is to consider its height to tip, meaning that unlike in the technique cited above, all functional-technical equipment is taken into account and considered as an integral part of the building. This measurement includes antennas, flagpoles, signage, etc. We do not use that method.
Finally, the third technique used and recognized by the CTBUH to measure the height of a building is that of the highest occupied floor. Here, the highest finished and occupied level of the building is the reference for its height. The CTBUH specifies that an occupied floor is a floor that is used by residents or workers on a consistent basis, and does not take into account mechanical floors.
We use that method to declare how many floors there are in a building. Most of the time that's straight-forward based on the plans for a building, but occasionally it means we differ from the count presented to a planning department. For instance, if the uppermost level of residences on a building is the 12th, but the mechanical penthouse above shares its level with an amenity space, then we consider the building to have 13 storeys, even if the municipality counts it as 12.
What do you think about these definitions and the way they influence the ranking of the tallest buildings around the world? Let us know by leaving a comment in the field below.
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Do you have other planning terms that you would like to see featured on Explainer? Share your comments and questions in the comments section below!
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Want to read other Explainers? Click on the magenta Explainer box at the top of the page.
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UrbanToronto’s new data research service, UrbanToronto Pro, offers comprehensive information on construction projects in the Greater Toronto Area—from proposal right through to completion stages. In addition, our subscription newsletter, New Development Insider, drops in your mailbox daily to help you track projects through the planning process.
