Which Zones Have The Tallest Buildings in New York City?

Last week, in my post about the correlation between allowable FARs and building heights, I mentioned that I would be delving deeper into which zones are home to the tallest buildings. That’s what I will be exploring in this article.

To the data!

The starting point, as is so often the case, is PLUTO data. I will be using the same data that I referenced in last week’s article. The data covers the entire island of Manhattan.

If you’ve read my last article, you already know that I’ve done some calculations about building heights by allowable FAR. I expanded that model to include zones and then sorted by building heights in order to figure out the tallest zones.

Here’s what I found:

Which zones have the tallest residential buildings in New York City?
Which zones have the tallest residential buildings in New York City?

This table shows zones on the Y-axis and allowable FAR along the X-axis. As expected from my last post, when we sort the zones in order from tallest to shortest (as I did above), we get a trend that moves up and to the right.

This trend exists because allowable FAR has a positive correlation with building heights. The higher the FAR, the taller the building, on average.

The column on the far right is added for reference as a measure of magnitude. It is the total number of buildings within a given zone in our sample.

This is how you read the chart. The first zone, C5-2.5, has a maximum allowable FAR of 10 (from the top row), an average building height of 32.0 stories (the green cell), and contains 9 residential buildings (the column on the right).

Next, I’m going to throw this data into Carto and do a visual spot check. Which 9 residential buildings are in C5-2.5? Does this make sense?

The residential buildings in zone C5-2.5.
The residential buildings in zone C5-2.5. (Color scale dictates height.)

If you know New York City real estate, the big red zone in the middle of the map will stick out like a sore thumb. That’s 432 Park, the 90-story residential skyscraper home to some of New York’s most expensive apartments. The dark orange building highlighted to its left is Museum Tower, a 53-story residential tower at 15 West 53rd Street. And to the south, just west of 3rd Avenue, is The Metropolis, a 48-story luxury rental building at 150 East 44th Street.

So it looks like we’re on to something. Simply modeling average building height by zone has enabled us to quickly isolate some valuable properties and create a hypothesis that zone C5-2.5 is great for tall buildings.

Warning: Digression Ahead

Now I want you to take a closer look at that map. Squint at the bottom left of the map between Park Avenue & Lexington Avenue and you’ll notice a very faint yellow rectangle. That’s 114 East 40th Street. And it’s only 9 stories tall. Weird.

In zone C5-2.5, we have 432 Park standing 90 stories tall, dominating the New York City skyline, and we have 114 East 40th Street rising just 9 stories.

Why? What other factors could create such an enormous disparity in building height?

Both buildings are C5-2.5 and both buildings are in the Midtown Special Purpose District (MiD). Zone clearly is not the only important factor in determining height.

432 Park’s lot area is about 10x the size of 114 East 40th Street’s lot area, but 432 Park has a building area of 745k SF whereas 114 East 40th has a building area of 26k SF — a 30x differential!

There is the added benefit of 432 Park being along a wide street, as explained in my post about setbacks. 114 East 40th Street was also built in the 1920s when the city was generally shorter.

But I think the key here, as reported by the New York Times in 2013, is air rights. 432 Park came with 115k SF of additional air rights before it was built. That enabled it to scale to great heights.

Unfortunately, there is no information about transferred or additional air rights in PLUTO data and I have not found a good source for this type of data, so we will have to live with the fact that we cannot account for air rights in our analyses automatically.

That said, we can still draw valuable conclusions. Zone C5-2.5 plus transferred air rights can lead to huge buildings. It’s something worth looking into for the other zones as well. For example, which sites are most favorable for applying transferred air rights?

Additionally, there is a lot more to building height than the zone in which a building sets and, therefore, there is a lot more to building height than allowable FAR (which is dictated by zone). Perhaps I’m inexperienced, but that’s news to me. The impact of air rights might be more meaningful than I previously thought.

Let’s get back on track.

That was a serious tangent. Valuable, but serious. Here’s the same breakdown for commercial land use:

Which zones have the tallest commercial buildings in New York City?
Which zones have the tallest commercial buildings in New York City?

It’s interesting that C6-6.5 has, on average, the tallest buildings, but it does not have the highest allowable FAR. I’m not exactly sure why that is, but I already bored all of you with one digression, so I won’t do it again.

Additionally, C5-3, C5-5, C6-6, C6-7, and C6-9 are all in the realm of 20-25 stories. If I were a real estate developer looking to build commercial skyscrapers, I would certainly focus on properties in these zones as a starting point.

In conclusion

This simple analysis has provided us with a foundation as to where the different zones stand in relation to commercial & residential building heights. I think it’s a quick and useful tool to help judge potential building height. On average, the zones towards the top of the list are going to be taller and inherently more valuable than the zones towards the bottom of the list. But that isn’t a definitive rule and it isn’t a suggestion that proper due diligence need not be performed.

As we saw with our comparison of 432 Park and 115 East 40th Street, zone is just one piece of the pie in attempting to figure out the key drivers behind building heights. I will continue to explore these drivers and use them to identify value where possible.

Setback Basics in the New York City Zoning Code

The New York City Zoning Resolution is a 3,917 page monster. Naturally, that can be both good and bad. On the bad side, you need a battalion of lawyers to understand it. On the good side, because of its complexity, the code is a tool through which creative developers can identify smart investments, differentiate properties, and create value.

One of those complexities is building setbacks. In this post, I will walk through the basic structure of specific setback requirements as dictated by the New York City Zoning Resolution and examine what they mean from a real estate development perspective.

Setback regulations force developers to push their buildings backwards as the buildings grow in height, similar to the tiers on a ziggurat or a wedding cake. Setbacks were mandated to ensure that streets didn’t suffocate between parallel rows of vertical towers and that sunlight could make its way down to the ground. If you keep your eyes open, you’ll notice setbacks everywhere.

The Paramount Building at 1501 Broadway is known for its setbacks.
The Paramount Building at 1501 Broadway is known for its setbacks.

The Paramount Building is a showcase for setbacks. You can very clearly see the tiers at the top and how the developable space was tapered back as the building grew in height. This is not just what setbacks are, but also why they are so important. They are one of the key factors in defining how buildings can grow, how space can be utilized, and how a property can be developed.

So, how do building setbacks work?

Unfortunately, there is no one cut-and-dry answer. To simplify things, I will focus on the following zoning code section and residential zones because I believe this section best represents the general concept & mechanics of setbacks:

Section 23-641
Front Setbacks
Zones R6, R7, R8, R9, and R10
(Page 378 in the NYC Zoning Code)

In the districts indicated without a letter suffix, if the front wall or other portion of a #building or other structure# is located at the #street line# or within the #initial setback distance# set forth in the following table, the height of such front wall or other portion of a #building or other structure# shall not exceed the maximum height above the #street line# set forth in the table. Above such specified maximum height and beyond the #initial setback distance#, the #building or other structure# shall not penetrate the #sky exposure plane# set forth in the table, except as otherwise provided in Sections 23-62 (Permitted Obstructions) or 23-65 (Tower Regulations).

This is how lawyers say the front of a building can only be a certain height and then the building must taper back.

The code has a nice picture to explain the requirement:

The Setback Concept: An initial height followed by a sloping boundary.
The Setback Concept: An initial height followed by a setback.

Then the code presents a table which outlines all the key variables and constraints:

The key variables for building setbacks.
The key variables for building setbacks.

The first thing you’ll probably notice is how ugly the table is. Move past this.

The second thing you’ll notice is that the variables are split depending on zoning. The top row is for R6 and R7 zones while the bottom row is for R8, R9, and R10 zones, but the only differences are with regard to the height of the front wall and the starting point of the sky exposure plane. The sky exposure plane slope and setback requirements are the same.

The third thing you’ll notice might be that it presents the same data twice–once for narrow streets and once for wide streets. What does that mean?

A “narrow street” is any #street# less than 75 feet wide.
A “wide street” is any #street# 75 feet or more in width.

This distinction is made to allow taller buildings on wider streets via steeper setbacks.

Depending on the width of the street the lot touches, you have to abide by the correct set of rules.

The fourth and last thing you’ll notice are the variables defined (from left to right on the table with variable names from the picture):

s = Initial setback distance (in feet)
Maximum height of a front wall
Sky exposure plane
h = Height above street line (in feet)
v = Vertical distance
a = Horizontal distance

Let’s dive into these variables and terms.

Initial setback distance
The initial setback distance is the minimum distance that the building must be pushed back once the building is as tall as the maximum height of the front wall. It’s worth noting that you can set the building back from the get-go or do small tiers on the way up (before hitting the maximum height of the front wall) if you desire. (It’s also worth noting that for these zones there are alternative setback regulations that can apply if a building uses a setback from the ground up. I will not be addressing those here.)

Maximum height of a front wall
The maximum height of a front wall is the tallest the front wall can be built before it must be pushed back by the initial setback distance.

Sky exposure plane
The sky exposure plane is like an invisible wall that defines the area under which your building must fit. Unless you are constructing a tower or using another exception (of which there are plenty), your building cannot break through the sky exposure plane.

The sky exposure plane explicitly limits the height of your building and defines how your building must be set back, so the location of the plane is extremely important.

Sky exposure plane height above street line
This is the bottom starting point of the sky exposure plane as it pertains to your lot. Regardless of how your building is built, the sky exposure plane always starts at this height directly above the street line.

Vertical & horizontal distance of sky exposure plane
These variables dictate the slope of the sky exposure plane starting at the sky exposure plane height above the street line. For every ‘v’ units moving up (vertically), the sky exposure plane is pushed ‘h’ units back (horizontally) from the street using the numbers shown in the table above.

What does this all mean? Let’s do an example.

First, we always start with our assumptions:

Zone: R7
Street Width: Narrow
Lot Area: 1,000 SF (25′ wide x 40′ deep)

Next, we’ll map out our setback variables according to the table above based on our assumptions. Remember, the only determinants of the setback variables are zone and street width, R7 and narrow.

s = 20′ = Initial setback distance (in feet)
60′ = Maximum height of a front wall
h = 60′ = Height above street line (in feet)
v = 2.7 = Vertical distance
a = 1 = Horizontal distance

To help visualize the sky exposure plane, I like to calculate what I call the top of the sky exposure plane. The code tells us where the plane starts (‘h’). This variable, ‘t’, tells us how high up the plane ends using our lot depth:

th* ( Lot Depth) = 60′ + 2.7 * ( 40′ / 1 ) = 168′

I find this easier to comprehend than the slope figures ‘v’ and ‘a’ alone.

Additionally, to help visualize building potential, I calculate the initial setback vertical effect. The code defines our first setback requirement. This variable, ‘i’, tells us how tall we can build directly after that setback.

Another way to look at it is it’s the vertical line that takes us from the sky exposure plane height above the street line up to the sky exposure plane after setting back by the initial setback requirement.

i = h* ( s / ) = 60′ + 2.7 * ( 20′ / 1 ) = 114′

With these two additional variables you can get a pretty good feel for how tall the building can be.

Finally, we can take a side view of our lot and draw out the boundaries under which the building must lie as dictated by the setback requirements. These boundaries are the red lines:

Plotting our setback requirements from a side view.
Plotting our setback requirements from a side view.

And there you have it. Exceptions aside (dormers, towers, etc.), the building you build must be contained underneath the red lines according to the setback regulations in Section 23-641 of the New York City Zoning Resolution.

What does this mean for real estate development?

In order to get height on your building within a setback zone, you need to be able to build up and back while maintaining enough space for livable apartments.

The implications of setbacks on developing residential real estate are therefore most substantially felt when dealing with lots that are not particularly deep, especially with respect to the initial setback distance. From a regulatory perspective, a site might have room to grow, but, in reality, the building might be limited to just the height of the front wall if the depth and setback requirement mix does not fit well.

For example, a lot that is 35′ deep on a narrow street might seem to have good depth, but because the initial setback requirement is 20′ and you would need space to construct the building and its elevator, the remaining 15′ of depth might not be enough space to build apartments. That could mean available space is under-utilized.

In this over-simplified situation, an extra 5′ of lot depth could actually be the difference between a few floors of apartments plus a penthouse and nothing.

Of course, this type of analysis would need to be done on a case-by-case basis.

Closing Remarks

Hopefully this wasn’t too dry and you now have a basic understanding of the way certain setback requirements work under the New York City Zoning Resolution.

Lastly, as I’ve mentioned a few times in this post, please be aware that this post is not meant to cover everything related to setbacks. It’s not even close. There are numerous alternatives, exceptions, and exemptions that enable smart real estate developers to get around setback requirements. I’ll be diving into these topics in the future.