Every city has tiny houses predating zoning and building codes. But San Francisco seems to have a particular affection for them. Photographer Richard Sexton, in The Cottage Book, chronicles many historic types. He also features new work by architect Donald MacDonald, who sees the cottage as a solution to affordability problems. MacDonald has designed freestanding studios as small as 14'x 17' and selling for $12-15,000, reasoning that the same people who rent studios and small apartments might want to own a similarly sized cottage with direct street and patio access. San Francisco, while endorsing high lot coverages, does not allow subdivision of large lots, so most of the cottages must be sold as condos.

The architecture school at McGill University in Montreal, meanwhile, is a hotbed of applied design in affordable housing. The school is careful to design for a wide variety of living and ownership arrangements. It has designed and built models with an eye on popular and commercial acceptance. A university product, the Grow Home, has been replicated 6,000 times in its various versions in the five years since its unveiling. A big plus is the open second floor, which residents shape with furniture and room dividers to suit their needs. The Grow Home was designed both as in-fill for 15' rowhouse lots and new construction.

Another design, “Next Home,” is a triple with a very low $27 per square foot construction cost.