We usually talk about the whole Seattle metro area on these pages, but I’d like to take a little while to discuss an issue that is most relevant to Seattle proper: Density.

There’s no denying that Seattle has been booming lately, thanks largely to serious growth in the local tech economy—unbridled growth at Amazon, the continued growth of local Silicon Valley outposts (e.g. Facebook, Google, etc.), and even the migration of large tech employers from other cities in the metro area into Seattle proper (e.g. Expedia)… you get the idea.

All of this adds up to the fastest population growth Seattle has seen since 1900-1910.

If Seattle’s population keeps growing, there is a hard housing reality that we’re going to have to face: the death of the single-family home.

As of 2013, roughly 43 percent of Seattle’s housing stock is made up of detached single-family homes. That’s already a minority, but if Seattle is going to be able to continue growing, that number is going to have to go a lot lower.

With 7,776 people per square mile, Seattle is currently the tenth most dense city in the country despite being only the twenty-second most populous. However, if Seattle is going to keep adding more people into the limited space we have available, we’re going to have to kiss an awful lot of our single-family housing goodbye.

No American city with 10,000 or more people per square mile has more than 25 percent of their housing as single-family. Here’s a look at population density versus single-family housing share for the 50 most populous cities in the United States:

If Seattle keeps adding people at the rate we’ve seen in the last few years, by 2030 the population will shoot up to around 900,000, equating to a density of 10,727 people per square mile. Even if none of the housing built to accommodate the population growth during that period is single-family homes, today’s single-family housing stock would still equate to roughly 31 percent of the total housing we’ll have in 2030.

I contend that this is not practically possible. Either Seattle’s population growth will dramatically slow down again in the near future, or we’re going to be tearing down a lot of single-family homes to make space for more townhomes and condos. Either way, it looks like the next ten years will be a very interesting time for Seattle.