A Deeper Look At Zoning

Regardless of your experience in real estate and construction, zoning is always a challenge to tackle especially in more urban environments. Most of this challenge is due to varying interpretations and nuances within the code. Every project must start with a zoning evaluation before designing. Violating the zoning can have severe consequences and relying on the zoning officials to catch any mistake is dangerous.

When reviewing your zoning it is important not to make assumptions no matter how obvious they may seem. Making assumptions can be costly when interpreting the code. The language in the code is intentional to cover all the bases and is littered with specific definitions, exceptions, and references to other sections of code. Look closely at the zoning and ask even the obvious questions before moving forward. Below are some examples of distinctions and assumptions to watch out for.

Please keep in mind these nuances may differ from your local code. Every zoning code has differences and are constantly changing.

Zoning Density

One of the first things we think about, apart from use, is how much we can build? There are a few methods most zoning codes use to regulate density.

Unit density – is the number of units per given lot size (usually per acre). Units can mean shops, condos, single-family homes, etc.

Floor Area Ratio (F.A.R.) – is a simple equation. F.A.R. x Area of Site = Allowed Building Area. As an example, if the zoning states an F.A.R. of 0.60 is allowed in a given zone this means that the total area of a building, and the sum of the total areas of all buildings on a lot, cannot exceed 60% of the overall lot area. This is a gross area figure which includes stairways, hallways, and other support spaces sometimes not included in other calculations.

Building Coverage – is the allowed area of a lot covered by buildings. In some cases, this includes any covering such as stairways, decks, bridges, carports, etc. Because this is a footprint calculation it does not have control over height like the F.A.R.

Density Bonuses – is an allowed increase to zoning density. Many zones allow for density bonuses for meeting other requirements. Some allow for an increased F.A.R if you provide a certain percentage of affordable housing. There are other bonuses for being within a certain distance of a transit stop. There are many ways to increase density. However, some zones only allow you to pick one bonus and do not allow adding multiple bonuses together.

Parking vs Density

Parking vs Density Study

It is not uncommon for other elements of the zoning to limit the site density. A big limitation in some cases is the parking requirements. Most zoning districts require a certain amount of parking allocated for each use. If you are unable to balance the parking with the allowed density, it may be worth reconsidering your approach to what goes on your lot. In many cases, developers are pushed to build parking structures to meet the parking requirements which of course has its own costs and requirements which usually only work in larger developments.

Lot Setbacks

Setbacks are imaginary lines on your lot which define where buildings and building elements can and cannot be placed. Most zoning ordinances identify which elements can and cannot be built in the setbacks. For example, elements like fences, overhangs, chimneys, and condensing units can usually be built into the side setbacks but may be restricted from the front setbacks. Although canopies can protrude a certain distance into the setbacks, balconies are typically not allowed. The list for what is and is not acceptable can be rather long. Here in Nashville, this section of the zoning covers everything from clotheslines to pool houses.

Front Setbacks – Front setbacks are a little different than the side and rear setbacks. Most of the time the side and rear setbacks are defined in the bulk standards. The front setback is usually defined by one of two ways. Either by the size of the front street or the position of the neighboring buildings (contextual setback). Contextual setbacks are usually determined by taking the average front setback of the surrounding neighboring buildings on the same side of the street.

Build to Zone – In some cases, zoning code may define a “Build to Zone” rather than a front setback. This simply means that the front of the building must be built in this zone. This zone is usually a set distance from the front property line.

Height Regulations

Building Height – When zoning states that the max building height should not exceed 45 feet in a specific zone, this sounds obvious. However, did you know that building height can be defined differently in each zoning code? As an example, the definition of building height in some areas states that the measurement must be taken from the average elevation of the existing grade at the four most outer corners of your building to the average height of the highest roof surface. The point is, making assumptions can be dangerous when interpreting the code even if the assumption is as simple as building height definition. The language in the code is intentional about covering all the bases and is littered with dead ends and obstacles. Look closely at the zoning and ask even the obvious questions, like definitions, before moving forward.

Step Back and Sloped Height Control Plane – A “Step Back” can be written as follows: The building shall not exceed 45 feet in height for the

Step Back

first 15 feet in depth and not more than 60 feet total. This first 15 foot is measured from the front façade of the building towards the back. A “Sloped Height Control Plane” is similar, however, the zoning may add an additional provision stating that the height limit gets consistently greater as you measure from the front to the back.

The images to the right show the build-able area of a site with a “Step Back” provision and a “Sloped Height Control Plane”.

Proportional Heights – This states that the building height cannot exceed a certain width to height ratio. For example, the building height cannot be greater than 1.5 x the building width.

The main reason for these height restrictions is to allow more air and light to reach the street level. This provides a more comfortable and healthy street environment.

Some Other Requirements to be on the Lookout For

Frontage requirements – These requirements can include a minimum number of windows, garage doors not allowed to face the street, and the building must have a front porch just to name a few.

Historic Districts – Historic districts must go through the historic commission for approval. Whether

Sloped Height Control Plane

you are renovating or building new, being in a historic district will limit many aspects of the design. If your project is located in a historic district it is always a good idea to start a conversation with the historic staff early. This will give you a good idea of all the restrictions and requirements to avoid future problems.

Urban Overlay Districts – Urban Overlays may include adjustments to parking requirements, density calculations, height restrictions and much more. Check to see if your lot is in one of these overlays. Sometimes these overlays relieve the requirements of the standard zoning.

Planned Unit Developments (PUD) – Planned Unit Developments (PUD) are specific zones approved by planning that allow for flexibility in the typical zoning code. There is a long process for getting this approval but may be a benefit to your proforma.

Buffer Zones – Buffer zones are areas on your lot not allowed to be disturbed due to its proximity to waterways. Some buffer zones can be disturbed but must be planted back with natural vegetation after construction, others are not allowed to be touched.

Accessory structures – These are buildings on your lot that do not serve the primary purpose. The best example is a detached garage. Accessory structures have their own set of requirements separate from the main building and are typically more strict.

Sidewalk Requirements – Some zones require you to update existing or build new sidewalks on your property. This can be a major cost to your project and has stopped a lot of development in suburban areas.

The complexity of zoning is one of the main reasons we decided to start our feasibility service. There is no other service that can provide you with a better idea of what’s possible on your site. Check out our services tab and our blog about feasibility for more information.

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