One year in to the city's controversial experiment with backyard cottage housing, the law allowing backyard cottages has not resulted in concentration of backyard cottages, parking nightmares, or the destruction of Seattle's single-family character, a new report concludes. The major caveat to that positive finding: Cottage housing is both relatively uncommon and expensive.

At a meeting of the council's committee on the built environment today, staffers and architects briefed council members on how the city's cottage housing ordinance has performed so far. Among the city's findings:

• Backyard cottages remain fairly uncommon. In the year since the council allowed them citywide, the city has permitted just 55 cottages, or the equivalent of less than half of one percent of the city's 123,000-plus single-family houses.

Additionally, those new cottages are spread all over the city, not concentrated in a particular area, as cottage opponents had feared. "There had been some discussion of having a dispersion requirement, or a minimum distance from one another, and this shows that we didn't need to go there," committee chair Sally Clark said.

• Although homeowners who build backyard cottages are allowed to seek a waiver from the requirement that they provide one parking space for their cottage (the waiver requires that there be a problem with the site, such as a steep slope that makes parking untenable), only three cottage builders have done so, representing just five percent of all the cottages that have been built.

This finding directly contradicts opponents' claims that cottage housing would eat up valuable parking in single-family neighborhoods. And it raises a larger question: Should developers be required to provide parking for cottages even when the people renting them (elderly relatives, young professionals) may not have cars?

Architect Tim Hammer suggested that making it easier for cottage builders to get out of minimum parking requirements could lower the cost of building cottage housing. "In all of the [backyard] projects that we've done so far, it would have been nice if we could have foregone that requirement," Hammer said.

• In a related conclusion, the study found that cottage housing is actually quite expensive---a typical cottage costs $300 per square foot to build, or $240,000 for the maximum 800-square-foot cottage. "A lot of people expect it's going to cost about $100,000," Hammer said. "It's certianly possible, but the construction has to be very basic, and the owner has to take on a lot of the labor himself."

"The cost issues are concerning and I think we will want to talk with the planning commission about whether there's a way to get these down,"  Clark said.

• Fears that allowing cottage housing would lead to a proliferation of mega-cottages looming over single-family homes have not been borne out. The average backyard cottage is just 540 square feet (of a range of 244 square feet to the 800-square-foot maximum), on an average lot of nearly 6,400 square feet. The average height of backyard cottages is 17 feet, from a range of 10 to 23 feet tall (including pitched roofs in some cases.)

Moreover, the majority of backyard cottages (58 percent) were built in existing structures (like garages), "buildings the neighbors are used to having around," city planner Mike Podowski said.

Read the city's whole report here.