Floor Area Ratio — FAR — is the most important zoning control in most commercial real estate development. FAR is the ratio of total building floor area to the size of the lot: a FAR of 2.0 on a 50,000 square foot lot allows 100,000 square feet of total building area, distributed across however many floors the other zoning controls permit. High-density urban zones often allow FAR of 10.0 or higher; suburban commercial zones typically allow FAR of 0.5 to 2.0; industrial zones vary widely depending on the specific use. Understanding the FAR available on a specific site is the starting point for any development feasibility analysis, and the difference between a 4.0 FAR site and a 2.0 FAR site can double the developable area and therefore the project's scale and returns.
FAR interacts with the other bulk controls to produce the actual development envelope. Setback requirements force the building away from the property lines and away from adjacent streets, reducing the usable footprint. Height limits cap the number of floors regardless of FAR — a site with 10 FAR and a 10-story height limit has a very different development envelope than one with 10 FAR and no height limit. Lot coverage limits restrict how much of the parcel can be built on, often as a percentage (60% coverage means 40% of the site must remain open). Open space requirements mandate specific amounts of accessible green space. The developer's architect works within this envelope to optimize the design against the specific FAR calculation rules of the jurisdiction, because different jurisdictions count floor area differently (some exclude mechanical space, some count below-grade space, some have separate rules for ceiling heights).
Density bonuses are a negotiation tool municipalities use to encourage specific policy outcomes. A base zoning might allow FAR of 3.0, but the same zoning might allow up to 5.0 in exchange for specific community benefits: affordable housing units, public plaza space, below-grade parking structures that free up street-level space, contributions to public transit, sustainable design features that exceed building code requirements. The bonus is often expressed as a specific ratio — 1 square foot of additional FAR per 3 square feet of affordable housing provided, for example — and can be the difference between a marginally feasible project and a highly profitable one. Density bonuses are especially important in mission-aligned discussions about housing supply, because they allow cities to extract affordable housing from private development without funding it through general tax revenue.
Transferable development rights — TDR — provide a way to move unused FAR from one parcel to another. A landmark historic building might be developed to only 2.0 FAR when the underlying zoning permits 10.0, leaving 8.0 FAR of unused development rights that the owner can sell to a developer in a receiving zone. The developer pays for the TDR, adds that FAR to their project in the receiving zone, and builds a larger project than the base zoning would allow. TDR programs have been used in New York for decades (Grand Central Station famously sold TDR from its air rights), in Toronto to preserve historic buildings in the central business district, and in Washington, D.C., for similar preservation purposes. The TDR market is thin, transaction-specific, and jurisdictionally complex, but for specific development sites in specific cities, TDR can be an important and sometimes essential piece of the feasibility equation.
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