South Lake Union and Denny Triangle

 

The NC3-85 and NC3-125 zoning designations (Neighborhood Commercial 3, 85-foot/125-foot height limits) are used extensively throughout Seattle. Ostensibly, the goal of NC3 zoning is to create large, pedestrian-oriented, mixed-use commercial districts. But in fact, these two designations are limiting Seattle’s ability to develop, while presenting the illusion that the city has more available building capacity than it really does.

To start, let’s compare the 4 different height limits used for NC3 zones. Suppose that there are four lots, each one 28,500 square feet and with a different NC3 zoning designation:

ZoningNC3-65NC3-85NC3-125NC3-160
Allowable Height65 ft85 ft125 ft160 ft
Approximate Maximum Story681115
Floor Area Ratio (FAR)4.75667
Lot Footprint Utilization4.75/66/86/117/15
Existing 28,000 sf Lot22,562.521,37515,545.513,300
Existing Developable Square
Footage for 28,000 sf Lot
135,375171,000171,000199,500
Ratio of FAR to Next ZoneN/A1.26 (+26%)1 (+0%)1.16 (+16)

It’s important to remember that height is not density. Imagine a parcel of land that is divided into two halves: one half has a one-story single-family home while the other half is vacant. If the homeowner builds a second-story addition and rents it out, they have doubled the density of their property. But if the homeowner simply builds another one-story home on the vacant part of the lot, they have doubled the density as well. Ultimately, the floor-area ratio (FAR)–i.e. the total amount of floor space that a building can have, given the size of the land it sits on–is a much better measure of how dense a neighborhood can get.

A new development on a parcel zoned NC3-85 can have 26% more floor area than if the parcel were zoned NC3-65. Despite this, NC3-65 remains the leader in new, low-rise development in Seattle. The reason for this is simple: geology. According to the United States Geological Survey (USGS), Seattle is in seismic category D. This designation limits the allowed heights of buildings that use wood for structural purposes (a.k.a. “seismic force-resisting systems”). In particular, buildings that use wood for bearing walls or building frames cannot be taller than 65 feet. Here’s an excerpt from the ASCE 7 Standard (American Society of Civil Engineers):

ASCE 7-10

 

If this seems weird, think about the opposite: how many 6-story buildings have you seen being built out of concrete or steel? Wood-framed buildings are cheaper and easier to construct, and so developers generally don’t want to use sturdier materials until they have to.

Given this limitation, every real estate developer must ask themselves, “Are two extra floors (20 extra feet) worth the hassle of concrete and steel?” For most developers, the answer is “no“. Instead, they choose to buy and develop lots with NC3-65 zoning.

The 125-foot height limit (NC3-125) is no better. In all Seattle commercial zones, the FAR limit for mixed-use 125-foot buildings (6.00) is the same as for mixed-use 85-foot buildings. While 125-foot buildings can be taller, they must be skinnier to compensate. Taller buildings can command higher prices for high-up units, but is that enough to recoup the expense of steel or concrete? I’d call that a maybe at best.

Only the 160-foot height limit (NC3-160) offers a meaningful improvement over NC3-65. Its FAR of 7.00 is over 50% greater than NC3-65’s max FAR of 4.75. And NC3-160 is nearly 2.5 times as tall as NC3-65, which allows for 7 floors worth of premium-priced high-rise units. Those premium rentals are key in helping the building “pencil out,” even with the added expense of concrete or steel construction.

As an aside, it’s worth noting that NC3-160 encourages good urban form in a way that NC3-85 does not. A 6-story building on an NC3-85 parcel can cover 100% of the lot. Too many of these “bread loaf” buildings can create an imposing facade. With NC3-160, if a developer were allowed to go “straight up”, over half of the lot would be undeveloped. In reality, developers follow the pattern used by buildings like Olive 8, with 2-4 stories of full-lot coverage and a skinnier tower on top. This urban form can feel more airy and inviting than full-coverage 6-story buildings, even though it’s actually denser than the latter.

While they have good intentions, the NC3-85 and NC3-125 zoning designations simply don’t live up to their potential. Construction costs and FAR limitations will prevent these zones from achieving the high density and good urban form that NC3 is designed for. If we’re lucky, the market will price these parcels at the same rate as NC3-65, and these lots will be redeveloped with needlessly short buildings. If we’re not lucky, then a lot of existing buildings, parking lots and “brown fields” will miss out on the redevelopment that they deserve.

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Caelen is a third generation son of Ballard. When he was in high school, his parents moved the family out to beautiful Bainbridge Island where he found himself missing urban life--homesickness for Seattle continued on into his college pursuits. Classically trained in structural engineering with an emphasis in earthquake design, he loves steel, glass, and concrete. He primarily writes about Ballard land use (hopefully home to future TOD) and Sound Transit packages, both emphasizing long-range planning.

17 COMMENTS

  1. Novice with peaked interest asks: I’ve heard we zone certain areas to maintain the view of the Space Needle (from Green Lake, for example). What areas apply to that and which don’t? And why?

  2. Is there any political will to upzone NC3-85/125 zones to 160, or increase FAR’s? If there isn’t the will right now, could be a mission worthy of our undertaking…Of couse I have no idea how you’d sell it to NIMBY’s.

    • One approach would be to structure it as a trade: upzone some parcels to 160, and downzone some parcels to 65, while keeping the total allowed FAR the same across all parcels.

      • That’s a great idea. One of the complaints I often here is that a lot of the new buildings look the same, or at least are the same shape (big bread loaves). This article is interesting, because it shows that it isn’t simply the zoning that forces this, but a combination of zoning and engineering.

        It would also be nice if the city somehow encouraged more construction next to existing buildings. A skinny building next to an existing building is a lot more interesting than simply leveling the whole thing and putting up a six story building. The National Sign building on Westlake is a good example. It is a nice looking building, and it looks like it will be preserved while they build around it. It would be shame, aesthetically speaking, to see it go. Even if you don’t care about aesthetics, and only want to increase density, you get a lot more opposition to increased density when you bulldoze nice looking buildings and put up buildings that more or less all look the same. This would also encourage replacing surface parking lots with buildings, especially when they are small, and next to existing buildings. As the author mentioned, this is a great way to increase density. There are a lot of these scattered around the city, especially in high development areas (I can see a few just by looking around the area I mentioned).

      • This is a good idea in principle to promote variety. But a challenge is that land use regs generally are structured such that properties in a district with similar location characteristics in the same area should be afforded equal opportunity to develop -> equal land values. A gov’t can’t really just sculpt the regs according to its ideal urban form – parcel by parcel – without regard to land value.

        The tool that’s needed to achieve this sort of thing is a local (within neighb) Transfer of Development Rights (TDR) structure, so the unused development on the non-developed parcels can be purchased by the parcels with access to greater height/FAR.

  3. I love articles like this. It’s really hard for non-experts to understand our complicated building and land use codes, yet they impact our city in fundamental ways. It’s important to help people understand why this stuff matters.

    Something else that might impact this are tall wood structures. I believe they’re difficult to get past our structural codes, but wood can be much more sustainable than concrete and steel, is cheaper, and can be just as strong or stronger in an earthquake if designed well.

      • Not at all. My designs involve boilers, chillers, and ductwork. Not the kind of thing you want to build out of wood.

      • In an earthquake fire suppression systems like sprinklers which rely on local water supply could fail due to interruptions of said supply. In an earthquake fires are known to be largest cause of damage. So rather than build taller buildings out of wood, let’s carefully consider upzones that make the robust reinforced concrete buildings pencil out. Obviously if your costs per unit go up, say, 10-15% when going from wood frame to reinforced concrete, then adding 2 more floors (65->85) may not need to a sufficient increase in revenue to bring back profit, but what about 95 ft, 105 ft?

  4. I should note that one of the reasons the city’s analyst cited as to why taller buildings were not going in SLU was that builders didn’t expect to get any increase in price on the units at a taller height than 60 feet. In other words the units would cost the same at 4 – 6 stories as they would at 7 and 8 stories.

    • The pipeline projects in SLU now are towers – such as the Seattle Times block, 9th/Republican, the lakefront blocks and a few others.

      • This is true but a lot, if not most, of them are below the max height allowed. The point the city’s analyst was making was that the premium pricing was already reached with at the height the buildings were built up to so there wasn’t any additional price premium for building higher.

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