Over on sister site MNN.com, Matt Hickman describes Blu Homes' latest model, the Balance Metro, as a home "specifically designed for installation on narrow urban and suburban lots." It's 36 feet wide! Given the standard sideyards that bylaws require, it probably needs a 44 foot wide lot minimum.
If you want to get the real skinny on narrow urban lots, have a look in Japan. This house in Nada, designed by Fujiwarramuro Architects, sits on a lot that's only 397 square feet.
It's so narrow that it is hard to tell if there is even a stair, but you can catch a glimpse of it at the end of the entry hall; it appears that the stair runs up the back of the house.
There is a price to be paid for putting the stair there; There isn't much privacy. To get to the kids room at the front, I think you probably have to walk through the other bedroom.
Even though the house is a tiny 681 square feet on such a small footprint, there is a dramatic light well running through it.
The view from above.
You can get a lot of density into a neighbourhood if you design the houses to be narrow. We need more of this in North America. More images at ArchDaily.