Among other changes, the new regulations set hard limits on the size and height of new single-family homes, and require certain trees to be saved on home-building sites.
Mercer Island, one of the most expensive real estate markets in the country, is limiting the development of mansions with new restrictions that go farther than any other local city in capping the size of huge homes.
The regulations, passed 5-1 by the island’s City Council late Tuesday, are the result of a yearlong effort to address residents’ concerns about gleaming new mega-homes towering over single-story ramblers built half a century ago. It’s the latest in a long line of fights in the town to limit development.
Most other cities in King County don’t restrict home sizes the way Mercer Island does, and those that do allow for bigger homes.
Home builders say it could push wealthy owners to build estates elsewhere in the region, increasing sprawl. And one council member who opposed the changes said the island could lose out on CEOs moving there.
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The new law only applies to future construction and major remodels of single-family homes — so houses that are already built won’t be forced to downsize, and apartment development won’t be affected.
Starting in November, the size of new houses will be capped based on how big the lot size is, with the largest houses still on the waterfront and smaller ones in the middle of the island.
Typically, homes will be limited to 40 percent of the lot size, down from 45 percent before. Since lots on the island are so huge, the change adds up: The median new house would be cut by 600 square feet, or 11 percent.
That alters the potential value of a home by hundreds of thousands of dollars. For instance, the typical Mercer Island home just under 4,500 square feet sold for about $2.03 million within the last year. But downsized to 4,000 square feet, the median house price falls to $1.78 million, according to Seattle-based real estate site Estately.
Evan Maxim, the island’s planning manager, said the changes were proposed after an influx of developers in recent years began buying smaller, older homes on large lots tearing them down, and putting up two big modern homes in their place.
The island has been getting about 250 new houses per year during the region’s current development boom.
“You might have a checkerboard of older homes and new…