At this point I don’t have much to add what Roger and Bruce had to say about Monday’s Committee of the Built Environment hearing, but I do want to make an observation. There has been a lot of people using the term “pro-density” or “anti-density” without actually qualifying what kind of density they mean. To some, the Roosevelt neighborhood already is their definition of a dense neighborhood, to others Fremont, Ballard or Capitol Hill are dense, and to yet others Belltown is the only example of actual density in Seattle.

So while people will say they are pro-density, what they actually mean by density is much more important. In addition, what people believe the additional density associated with a new Link station should be, over what that neighborhood should otherwise have, is almost never addressed. These issue are compounded by the fact that by in large part single family zones are off the table when it comes to rezones, focusing and compounding growth into a small area.

Below is a post by Dan at his old home at HugeAssCity on the topic.

Much of the heat in the debate over urban density arises from a lack of understanding of what the metrics correspond to in the real world.  Below is a series of slides presented at a public hearing on HB1490 by a colleague of mine from GGLO, that illustrates a wide range of densities, i.e, Density 101 for Legislators.

The first two slides address the difference between gross density and net density — this has been a source of confusion for HB1490 opponents, as discussed here.

More after the jump.

The following eight slides illustrate net densities ranging from 14 to 220 dwelling units per acre (DU/AC).  Keep in mind that the proposed 50 DU/AC threshold in HB1490 is defined in terms of the net density allowed by zoning.

(Some or you smarty-pantses may recall that in this previous post I claimed that the net density in the Rainier Vista building shown above was about 100 DU/AC.  My guess was high because I wasn’t considering the 3-story north end of the building, and also because I didn’t realize there is so much surface parking on the parcel.  Go here to see an example of a 3-over-1 building with a net density of 99 DU/AC.)

39 Replies to “Density, An Ill Defined Term”

  1. Do we have figures on densities in Vancouver style neighborhoods? (I.e. towers and one story platforms) Its hard to compare something like Metrotown to any of these.

    1. Density also depends on the the size of the individual units. I have read that many of the towers in Vancouver have smaller units, though I don’t know how they compare to towers in Seattle.

      The QA/Uptown building I currently reside in is a 3 story walkup which has 13 units on a 0.15 acre lot or 87 DU/AC. The units are all 1 bedroom except for one studio unit. We also have a parking lot behind and a small garage underneath.

  2. Excellent post. Had a bunch of density advocates gone and talked to the RNA about this, and shown what airy, pleasant high density can look and feel like, and the benefits it can bring to the area, we could have avoided most of this drama and unpleasantness. Only problem: it needed to happen in 2006.

    1. No it didn’t. We can change these laws whenever we want to. That’s Democracy.

      I’ll make a wager, Bruce. The zoning around Roosevelt while change again in the before the station opens (10 years).

      1. Yep, we’re just going to push for another increase again soon. And another after that. And another after that.

      2. No it didn’t. We can change these laws whenever we want to. That’s Democracy.

        We don’t live in a Democracy. We live in a Republic. We elect (or don’t elect) political leaders to make these decisions based on shared beliefs.

      3. The majority of the Bellevue City Council appreciates your support of their position that we should return to the drawing board on East Link in light of the rising vocal minority opposition to Sound Transit’s East Link plan.

      4. Kyle, you have it completely backwards. In both the Bellevue city council and RNA you have a vocal local group holding up regional progress.

      5. We don’t live in a Democracy. We live in a Republic. We elect (or don’t elect) political leaders to make these decisions based on shared beliefs.

        Let’s be as pedantic as possible, and also slightly wrong while we do it by ignoring that we have direct democracy as well.

    2. I hope you’re right, but from my engagement with planning around Capitol Hill I feel you’re on the optimistic end of the spectrum.

      When I think of a “model” TOD this is roughly what I have in mind. Immediately around the station (1-2 blocks) net housing densities in the high 100s and low 200s (depending on the existing intensity of use), low 90s 2-5 blocks out, dropping to 30s a quart mile out and 15 a full half mile out.

      Unfortunately I don’t think most community groups share my opinion, no matter how much I talk to them.

    3. Any RNA proposal, no matter who showed up with pretty posters of tall buildings, would still have to reflect the narrow bias of the group.

      I really don’t believe that it’s the job of anyone to convince a few hundred homeowners around a future subway station that, no, they really *do* want tall buildings.

      When you start a planning process with the values and assumptions of the group set in stone, you get predictable results. The point should be to start a process in which those very values and assumptions are debated vigorously by a variety of stakeholders. The venue for that debate is *never* a neighborhood association like the RNA.

      1. In general we need to keep in mind that most neighborhood groups like RNA or even the Capitol Hill Community Council (I was an officer last year) are not actually representative of the people living in that neighborhood or the people who would like to live in that neighborhood. A neighborhood council is a special interest group comprised mainly of property owners and long-term residents. The only reason the CHCC has a lot of young people involved is that a lot of young people manage to rent in Capitol Hill for many years and because the neighborhood attracts a lot of urban planning types like me. Most neighborhood councils are very different–they skew older, wealthier, more established. As far as city planning goes, neighborhood councils are only one of many many stakeholders that should be consulted. The RNA should never have been allowed to craft their own zoning proposal–DPD should have followed the normal practice of consulting the neighborhood council and many other groups in order to craft a proposal.

  3. What’s interesting is that one can achieve significant density without towers.

    I wonder if thinking towers as a requirement to achieve density increases is getting in the way – they’re not really required. If you run the math on what Adam’s describing, converting to gross density and putting a person(s)/dwelling factor into the number you’ll be amazed.

    1. If mid-rise buildings aren’t used you can get a good amount of total housing still, but to do that you have to have *more* area, sometimes much more, to achieve the same total quality of housing.

      Lets take the highest density Belltown example. One acre (lets use a standard unit of blocks instead) equals 220 units. To get the same with the other housing densities (by picture) you would need:

      – Single family, 23 blocks
      – Townhouses (2 floors), 16 blocks
      – Lion’s gate (3 floors), 6 blocks
      – Belmont (3 floors high density), 5.5 blocks
      – Rainier (4 floors) Vista 3.3 blocks
      – Burien (5-6 stories), 2.5 blocks
      – Brodaway (5 floors, small units, low parking ratio), 1.6 blocks
      – Cabrini (6 floors, senior housing), 1.4 blocks

      So yes you can do it but there are trade offs.

    2. I see towers as an easier path to density in built-up areas. Start with a blank slate, and an area with 5-story buildings could easily be high density. But start with existing construction, and it could take decades and decades to get there as developers and owners work out what buildings are old enough or small enough to demo and start over. Put one or two towers in, however, and you’re there in a few years.

      That said, towers seem to scare people. I’ll take what density I can get.

    3. In general towers scare people a lot more than midrise, and I think there are good reasons for this. One is that highrise has such incredibly high construction costs and poor energy efficiency that the rents end up being very high. Developers mainly like highrise because they can attract the “luxury” market. Many people are concerned about upzones because they lead to new construction, which is always more expensive than older buildings. Midrise buildings are more likely to have a mix of luxury and affordable units with smaller units overall, so they are more palatable from an affordability perspective.

      Most affordable highrise consists of government-funded “projects.” This gives highrise another stigma from the other end, as some wealthy neighborhood folks associate them with poverty.

      If you care at all about energy efficiency, do not support highrise. Skinny towers expose more surface area to wind, sun, etc and are a lot less efficient than breadbox midrise buildings.

      This last point is subjective, of course, but midrise seems to strike more people as having a human scale and a better streetscape. Paris and much of New York City consist of blocks and blocks of midrise, and it creates a really nice urban form. Vancouver’s West End to me feels like a playground for the rich, not a real neighborhood with an active streetlife. All the setbacks and plazas required to space out highrise buildings results in a lot of empty dead space.

      1. Where are you getting the idea that high rise has poor energy efficiency? Compared to what? It’s miles above (haha) single family. And how about the energy efficiency of replacing a car trip with a transit trip…?

      2. I agree with Ben. Actually, we’ve wandered into my area of expertise, and I can tell you that highrises perform identically to mid-rises from a skin-load perspective, and can be significantly more efficient on the equipment side. Large equipment is generally more efficient than small equipment, so efficiency rises with height. The two areas where highrises can lose energy are in pumping water (a comparatively small load) and elevators (which are quickly moving toward energy-harvesting strategies).

        By far the largest changes in energy use for either of these types of buildings are choices made by the architect and developer. Whether or not they have balconies*, for instance. Or the amount and quality of the glass.

        * these fins are perfect for exchanging heat with their environment – good if you’re designing a radiator, bad if you’re designing a building.

      3. We live in a particularly mild climate, though, so the effect of balconies can’t be nearly as severe in, say, winter in Boston.

      4. @Matt. Yeah balconies, especially concrete ones, act essentially like a radiator or heat sink on a processor, with a high surface volume to mass ratio.

      5. The “balcony = radiator fin” analogy only seems apropos if the balcony significantly increases the surface area (which is the point of a radiator fin after all). Just eyeballing a photo of a high-rise with balconies, I’m guessing its balconies have 10% or less the area of non-balcony surfaces…

      6. Most of the new buildings have what I call fake balconies. A deck that may or may not be deep enough to stand on, or just a railing and no deck at all.

    4. It all depends on what you classify as “significant”, of course…. and how much existing super-low-density housing is going to get lumped in with the new construction, driving the numbers down.

  4. If the city doesn’t end up changing the zoning around the station, the increase in property values will almost certainly necessitate it later.

    Even if the station area remained single family housing for the next 20 years, we’ll still be alive. Everything will be okay.

    1. Except we are spending a lot of money for that light rail station. It would be nice if more people could live near it and use the thing.

      1. But this wont happen. Lots will be developed, developers will buy single family houses and rebuild multi-family. It will take 10 – 30 years but so what? The station will still be there one hundred years after it opens.

      2. In the case of Rosevelt, there is at least one deveopler who is already trying to build bigger property to replace what is already there. He is stopped by the zoneing restrictions. These restrictions have to be changed in order for anyone to build more density. However the neighborhood seems to have a personal problem with this guy and does not want him making money by developing the property he owns.

        At least that is what i see is happening.

        I do not live near rosevelt but if they developed it into a nice dense community centerd around the light rail station, i may try to move there.

  5. Responding to Matt’s comment about balconies being radiators…let’s remember
    buildings should first be designed to house people, not be just glorified mechanical systems that are called buildings.

    1. If a balcony increased the rental price of an apartment by $500/month, would you take it? Would everyone?

      Not saying it would have that severe of an impact, but I am saying that decisions like these are important. We don’t have unlimited resources, and everything we spend money on (like balconies) has an opportunity cost.

      Matt’s point — and a legitimate one — is that the reason that many high-rises are expensive has almost nothing to do with the fact that they’re high-rises, and everything to do with the fact that the developer chooses to spend money on amenities.

  6. I’m not a supporter of the RNA plan, but – aside from the three blocks South of Roosevelt High School – what’s the big difference between the RNA plan and the mayor’s plan?

    1. Not a whole lot. The biggest difference between the Mayor’s proposal and the newest RNA proposal is a 1 1/3 block mid rise zone next to I-5. This is why this whole debate is such a joke, we’re arguing over 20 ft here and there. Its a total travesty.

  7. Sometimes I wish this blog was a little more informative about the issues at hand – can someone spell out what the main differences between the two plans are? What some likely or potential outcomes are? There have been four recent posts about the Roosevelt upzone, but none have given even a broad overview of the different plans and exactly what they entail.

  8. adam–
    excellent post with good info + great illustrations.

    could you (or someone else?) please weigh in and try to offer some rough aproximations of what density (DU/AC number) we would expect from a developement built out in each of the principle seattle DPD zoning catagories?

    L1, L2, L3, MR, NC2-40, NC3-65, NC3-85

    I realize there are potentially alot of variables with any given site, development, structure so a single DU/AC number may not be able to be equated to these zoning catagories. Perhaps you can offer a range?

    I see “FAR” numbers given in the DPD literature which describes the different zones. Can that be used to roughly deduce density?


    DPD zoning charts, see:

    1. Yeah so from my understanding the multifamily code update now focuses much more on FAR (floor area ratio, the square footage of the building divided by the square footage of the lot) than units, so the relationship depends on the situation. For example the number of units per FAR for a townhome will be lower than apartments because townhomes are larger. So their is a relationship between the two, but you have to make some assumptions.

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