For the first time (at least in recent history), less than half of all housing units in Seattle are detached single family dwellings. That’s what I found yesterday, squirreled away in the depths of recently-released census data for 2005. Just 49.3 percent of the city’s units are of the traditional house-and-yard variety.

And as far as I can tell, Seattle is the only city in the US Northwest where this is true. (The census numbers are easily available only in a format that makes it difficult to be certain.) Even in density-friendly Portland, fully 60 percent of the city’s housing units are conventional detached single family houses.

I should mention, however, that while Seattle has passed the halfway mark, detached single family houses are still easily the most common form of housing in Seattle. But I was equally surprised to find that 34 percent of all units in Seattle are in a building containing at least 10 units.

It’s interesting, I think, that the city’s image of itself hasn’t necessarily caught up to its new reality (as evidenced by the ritual of sackcloth and ashes still occasionally observed whenever urbanization is the topic). And while Seattle is still far less dense than, say, San Francisco, where only 16 percent of units are detached single family dwellings, I think we in the Emerald City can now officially consider ourselves urban.

UPDATE 4/16/07: Knute Berger, in a Crosscut column yesterday, says he doesn’t like this post. He doesn’t like Sightline’s support for increasing density in certain ways. And San Francisco? Don’t even get him started on San Francisco. Basically, it’s just Berger continuing his pro-sprawl propaganda campaign by rehashing a few half-baked (and thinly supported) notions about how density, affordability, and sprawl interact.

For a more complete history of the disagreement—which doubles as a handy index of the ways that Berger is wrong!—see here, here, here, and here. And some related stuff here, here, here, and here.

I or Clark will post a full response later on.

UPDATE 4/17/07: Berger gets called out by Ryan over at Metroblogging Seattle; also by Will at Horsesass. At Slog, Dan Savage is, um, emphatic about his disagreement with Berger. And then more recently at Slog, Erica C. Barnett delivers the coup de grace.

UPDATE 4/19/07: Michael van Baker takes it to a new level at Seattlest.