The result is a fairly dense building style that can easily triple in density over time. The developer doesn’t have to worry about land rights, since he sells it to one owner. There are likely land rights issues later, but that can be solved with good codes (maybe copied from San Francisco codes).

apartment.

Yes, it’s 60% lot coverage (very often increased beyond 60% through departures in design review) for townhouses vs. 50% for buildings of flats.

Tony: thanks for explanation. Wasn’t the SEPA threshold recently raised from projects of >8 units to projects of >30 units in at least some zones,including urban villages?

the building energy difference between a 1000 sqft townhouse and a 1000 sqft single family bungalow is negligible.

No.

The difference is that the SFD uses ~34% more energy due to lack of shared walls, holding sf constant.*

In addition, one can make light-colored roofs, increasing albedo. One cannot plant light-colored grass to shade the ground; thus heat capacity is increased in a large-lot scenario, increasing the heat island effect.

We also have the issue of road miles in SFD. If we are going to have suburban SFD, the most efficient way is smaller lot sizes and narrower streets shaded by deciduous trees.

Both of these approaches would achieve the same average density throughout the city and have the same effect on the sprawl impacts you identified.

This presumes everyone wants to live this way. This is not the case.

Maybe when gas is $12.00/gal. or we’re way past peak oil and transportation sector shrinks; both scenarios are a generation away. No narrowly prescriptive policy can get enacted without the flexibility of the ~25% demand for SFD in the future (e.g. Chuck Nelson’s projections).

Good comment thread!

————-

* Friedman 2007 pg 148 (Fig 5.11).

The U-District is, I believe, a good example of what I’ll call pseudo-single family zoning. Once upon a time (early 20th Century) it was true single family housing. Small lots, small houses. However, more recently a very large percentage of the houses have turned into rental properties. Some are rooming houses that are no better than slums (1 bathroom for 12 occupants, etc). Others are extremely well kept duplexes or triplexes. There are also still some actual single family houses. Lately you can mix in developers who see that townhomes equal dollar signs for the reasons Tony described (at least two sets on 12th Ave NE that I can think of, with more on 11th and Brooklyn and so on). In this context the current zoning makes no sense–especially considering this land will be within walking distance of two stations: Brooklyn Station at 45th and Roosevelt Station at 65th!

However, a similar distance from Roosevelt Station is the Ravenna neighborhood east of 15th Ave NE that never went through the rooming house transition. The important thing to notice is that on paper it looks the same as the U-District–small lots, houses built before the Depression. In my opinion Ravenna SF (and similar) should be protected. This is a close-in walkable neighborhood that I can’t afford to live in, but I’d love to someday. As far as I know, the only permanent option available is the National Historic District process, but the city design review process provides some help.

It seems to me there’s a middle path to preserving SF neighborhood structures and character while allowing increased density. Suppose new construction in SF zones must be single-family, but houses in SF zones that have stood for 20 years or more may be converted to duplexes without requiring zoning changes. Historically, this has been allowed — there are duplex conversions all over lower Wallingford — and units in such duplexes make comparatively affordable housing.

I suspect the biggest objection to this would come from neighbors who see street parking as their Deity-granted right and assume that conversion will remove street parking (which, in fairness, it probably would on the average). Maybe some kind of education or other mitigation (e.g. a duplex conversion must be accompanied by a $2000 donation to a neighborhood fund) would be this acceptable.

You make some good points and I do have to admit that even small SF houses are probably more energy intensive than most multifamily.

I also hope I’m not coming across as an SF purist. I live in a midrise apartment on capitol hill, so I’m doing my part. I also think that there are certain SF areas that do need to be upzoned, particularly those near rapid transit stations and streetcar lines (if they are ever built).

I think we should also remember that not all SF zones are created equal. I find SF 9600 a lot more offensive than SF 5000, and most SF zones in the suburbs are even larger. Single family is fine with me, but half-acre lots are ridiculous.

So I really agree with DanB’s post, SF is not sacred. I just think we should pick our battles and there may be other targets that yield a higher return on our efforts, such as the UV strategy and limiting lot size in the suburbs.

Re: DanC

Wow, there are so many Dans on this blog. There are two major factors that distort the market in favor of townhouses rather than small apartment/condo buildings:

First, and most significantly, townhouses fall below the SEPA and design review threshold. Both these processes are costly, so Seattle exempts small projects. Obviously there should be some cutoff where design review kicks in (you wouldn’t want to force somebody to go through design review to build a tool shed in their back yard for example), but by placing the cutoff where it is, it makes townhouses (below the threshold) cheaper to build than condos (above the threshold). There are two solutions: lower the threshold so that any multifamily construction requires design review, or raise the threshold to exempt small condo/apartment projects. Because design review (and SEPA) is SO expensive, we will always see a bunching up of projects just below the line, wherever we draw it, but draw it low enough and you will actually encourage higher density development, because if a developer has to do design review anyway, they may as well spread the cost out over a larger number of units.

The second reason developers like townhouses is that because they are not stacked vertically, you don’t have to deal with the joint ownership hassles of a condo building. Essentially, for a four-pack, the developer just subdivides the land into four super-small lots, each of which is taxed and owned separately. It’s like quasi-single family from an ownership perspective. This saves administrative hassles for both the developer and the homeowners initially (which is why they like it), but creates all sorts of problems in the long run because the owners of townhouses do in fact share walls, but they lack the joint ownership agreements that come with condos. So what, do you do if you need to replace a roof? This rule also needs to be changed so that all owner occupied multifamily housing is structured the same way.

Changing these two policies (which are arbitrary, city policies set by the City Council) would eliminate the artificial bias toward townhouses and allow the market to function without distortion. The result would be fewer townhouses and more stacked flats. There would still be some townhouses because some people really do prefer them, but most of the townhouse construction owes to the market distorting policies described above rather than true market demand.

SF houses are being replaced by multiple townhouses, and the area of truly impervious surface is generally increased. Large trees are lost with no opportunity for replacement in kind, as there usually isn’t enough open space configured for a large tree. Townhouses are allowed greater lot coverage than apartment buildings in Lowrise 3, where lots of them go. More bacteria in the Sound.

What drives townhouse as opposed to small apartment/condo building construction? Do the economics really preclude the latter?