The Seattle City Council unanimously passed legislation Nov. 2 that will allow detached accessory dwelling units, known as backyard cottages, throughout the city.

"I think this legislation strengthens our neighborhoods instead of damaging them," councilmember Tim Burgess said.

There had been some public resistance to backyard cottages at meetings and public hearings held since August, but councilmembers said they heard more positives than negatives.

Backyard cottages have been allowed in southeast Seattle since 2006, during which time 20 have been built.

A survey of residents near backyard cottages in southeast Seattle showed they largely felt no impact from the cottages, councilmember Sally Clark said.

She said 75 percent of speakers at a September public hearing were in favor of the legislation.

A number of nearby cities, such as Redmond, Shoreline and Kirkland, allow backyard cottages.

"The experience has been good in other cities; it's been good in southeast Seattle," Clark said.

Burgess said the legislation could be a positive way to create more affordable housing in the city, and council President Richard Conlin said backyard cottages could put more eyes on the street, creating safer neighborhoods.

The council placed a number of regulations into the legislation to control the construction of cottages.

New units can have a footprint of no larger than 800 square feet and can cover no more than 35 percent of the lot.

Cottages will only be allowed on lots that are larger than 4,000 square feet.

The new structures can be no taller than 22 feet, unless they are located on alleys or lots that are larger than 50 feet wide. In which case, they can be 23 feet tall.

Cottage height is also limited to 15 feet taller than the main house.

The property owner must live in either the main house or the backyard cottage for at least six months of the year. The council said this will control the quality of the new structures and the types of people who live in them.

The council sought to preserve the nature of the single-family zones in which cottages would be allowed by keeping the code limiting lots to housing no more than eight unrelated people.

"There is no change being made to the overall density that is allowed in single-family zones, just the way it is broken up on the lot," Clark said.

In one of the more controversial amendments to the legislation, the council removed the parking requirement for backyard cottages located within urban villages or urban centers.

The original limit of 50 new cottages citywide per year was also eliminated. Clark said the limit was pointless as the council does not believe the city will come close to reaching that number per year, though they will be monitoring permitting closely.

Conlin said the 50-unit cap may have had the opposite effect by causing a rush to the permit counter, leading to an increase in poorly thought-out units.

There will be a grace period until June 30, 2010 for any illegal backyard cottages to be inspected and get permitting.

The council commended the large amount of community outreach that was done prior to the legislation.