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.
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When a development application is submitted to the planning department, it contains pertinent information regarding the proposed structure. The height, total gross floor area, and lot coverage—the percentage of the property to be occupied by buildings—are attributes that are typically specified in the application's data sheet. Figuring out the proposed density of the development is a little trickier, but can be determined by calculating the floor space index (FSI).
Also known as the floor area ratio (FAR), FSI is the relationship between the total amount of usable floor area and the total area of the property on which it stands. It is determined by dividing the gross floor area of the building by the gross area of the lot. For example, a 10,000-square-foot building on a 10,000 foot² lot will have an FSI of 1.0, whereas a 50,000 ft² building on a 10,000 ft² will have an FSI of 5.0.
A one-storey building occupying the entire property, from lot line to lot line, would have an FSI of 1.0 — the same as a two-storey building occupying 50% of the property and a four-storey building occupying 25% of the property. This scenario is outlined in the image above.
Local governments use the FSI of a building as a density measure: a higher ratio indicates a denser development. Where land costs are high, developers need to build at a higher FSI to cover those costs. Downtown areas, which are typically highly sought after locations for both office and residential buildings, typically foster much higher FSI construction.
Have any other construction and development terms that you would like to see featured on Explainer? Share your thoughts and questions in the comments section 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.