An article on GoBankingRates discusses The Secret Costs to Owning a Tiny Home. You might want to read that if you're planning to live in a small over priced shack. But while reading that I noticed they start out saying "... tiny house movement is sweeping across the U.S ...". I'm not really sure what "sweeping" the nation means. But I tend to think this implies a lot of people are doing it, rather than just talking about it.
The American Housing Survey for 2013 has summary table data. Looks like that data is from 2010 so its not exactly brand new. But its the newest we've got to look at for now. If you dig around the XLS sheet with all the tables we can find on tab C-02-AO that they give both the square footage of houses and break to down by the new construction within the past 4 years. From there we can see that 26 thousand of the total 1,960 thousand new construction homes are under 500 sq. ft. Therefore 1.3% of new homes built in the previous 4 years were under 500 sq.ft. Of those, we don't know how many are just tiny studio apartments in NYC versus the small single family, cute shacks which are what we all consider to be Tiny Homes. But it is certain that the number of very small homes of any nature are a very small portion of the total new home market.
If you look at the AHS tables for specific metropolitan areas we can see if the trend of small houses might vary based on city. Looking at Seattle I see that 0.4 thousand out of 47 thousand units are 500 sq. ft or smaller new construction. Thats just 0.85%. Smaller even than the national average. Likewise in Austin the figure is 0.2 thousand out of 30.8 thousand. Thats 0.65%. Even fewer. In New York City on the other hand there were 3.7 thousand such small housing units built out of 57.8 thousand total which makes it 6.4% of the sum. I don't know for sure but when I think of a Tiny House I'd expect to see a bunch of them in Seattle or Austin and hardly any in NYC. The land in NYC is more expensive than anything else so building a shack trailer on super expensive land has no real benefit. I expect that small studio apartments in NYC accounts for a lot of that and they are probably raising the national average.
That gives the % of new homes under 500 sq. ft. as :
I don't think the Tiny Home movement is really sweeping anything other than headlines in a certain subset of blogs.
Yeah, I'm looking at old data and I suppose the trend could have developed more over the past few years, but I really doubt it.