Hoping to staunch the spread of megahomes into Seattle's bungalow neighborhoods, the Seattle City Council on Monday limited how much house an owner can build on a small lot.

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Hoping to staunch the spread of megahomes into Seattle’s bungalow neighborhoods, Seattle City Council on Monday limited how much house an owner can build on a small lot.

“While megahouses have not been as big a problem in Seattle as other communities, it has raised a lot of questions,” said council President Richard Conlin, who initiated the legislation.

“This is like an inoculation we were hoping to do to prevent spread of this problem.”

The new codes, which apply to single-family-zoned properties smaller than 5,000 square feet, are aimed at shrinking oversized homes that fill too much of their postage stamp-sized lots.

Residents have complained of giant houses that do not fit the character and scale of the neighborhood.

The council also hopes to reduce sidewalk space dominated by garage doors.

The facade “should read as a house, more than just a home for cars,” said Sally Clark, chair of the council’s land-use committee.

The council unanimously made the following changes:

• To make the footprint of a home more proportional with the lot size, owners of a single-family zoned property smaller than 5,000 square feet will be limited to building on 1,000 square feet plus 15 percent of the lot size. Previously, those owners could cover 1,750 square feet. A home’s total square footage may be greater with multiple stories.

• Lots with steep slopes greater than 30 percent will be limited to at most 5 feet of additional height. Previously, they were allowed more height based on the steepness of the slope.

• The new building rules also address garage doors that dominate the front-facing side of a home. Garage doors can no longer exceed 50 percent of the width of the street facade.

• To encourage parking on the back side of a property, the city will waive parking requirements for lots less than 30 feet wide or smaller than 3,000 square feet that do not have access to an alley.

The city’s planning department estimates the lot-coverage changes will affect 600 building applications a year and the garage limitations will affect 500 applications.

Council members called Monday’s changes a first step. Some hope to address megahomes comprehensively on all single-family properties by switching to a floor-area ratio measurement, more commonly used in commercial codes to limit a building’s bulk and scale.

The council adopted a resolution a few weeks ago directing the Department of Planning and Development to propose the change by January 2010.

Sharon Pian Chan: 206-464-2958 or schan@seattletimes.com