Cabins above 11,000 feet in elevation will be limited to a maximum of 750 square feet under land-use regulations adopted unanimously by the San Juan County Board of Commissioners on Wednesday.

But the board refused to go along with a Planning Commission recommendation to limit home sizes below an elevation of 11,000 feet to 2,000 square feet.

And the proposed regulations would allow property owners above 11,000 feet to add another 250 square feet to their structure if they demonstrate sensitivity to the viewshed impacts through use of materials, siting, and height limitations, or if the property owners provide public benefit such as trail access, or retiring development rights on another mining claim.

The new regulations were designed to address concerns about the impact of development on the hundreds of mining claims in San Juan County’s backcountry.

County commissioners last summer imposed a moratorium on approving new land-use proposals above timberline.

The moratorium was imposed after a Houston attorney last summer proposed a 5,000-square-foot home above timberline in the Mineral Point area. The county commissioners rejected that proposal and subsequently were served with a lawsuit, which is still pending.

Commissioners at that time said they needed to formulate more specific rules for land-use applications in the sensitive high-alpine tundra.

“We had a project that was the fuel that lit the fire,” said County Planning Director David Michaelson.

Michaelson noted the county has more than 3,000 patented mining claims. While several of those properties are not suitable for building because of steep slopes and avalanche hazard, perhaps 1,100 could be developed.

“There are a lot of concerns,” Michaelson said. “Visual impacts, health and safety.”

Michaelson said the new regulations are “pretty commonsense changes to the code.

“If you have to helicopter in construction equipment, that tells me it’s not the most appropriate place to build a house,” Michaelson said.

About a dozen people attended the county commissioners’ public hearing on the issue Wednesday night.

Dean Bosworth, an engineer from Silverton, said he felt the square-footage limits were too tight. He said he had two clients who currently were planning homes that would be out of compliance with the regulations.

Lisa Richardson of Silverton applauded the new regulations, but she added, “I remain against residential development above timberline. This is a step forward.”

Paul Joyce of Silverton said he, too, felt that “homes above timberline are a bad idea.”

Cynthia Chertos of Silverton had concerns about water and septic systems at such high elevations and whether they would be reliable enough to assure no environmental damage is done.

“If someone wants a large home, then being down in the valley is where they have to be,” Chertos said.

Bill Dodge said the county was left with a unique situation, with a hodgepodge of private mining claims in some of the areas least suitable for development.

He supported the idea of trading development rights on the high alpine claims with more appropriate locations in the valleys.

Pete Maisel, a construction company owner in Silverton, said he has several clients who invested tens of thousands of dollars in driveways and other work who now fear the projects were pointless.

“Several of them are concerned that this proposal may devalue their property before it’s even on the market,” Maisel said. And he expressed concern the new rules could open the county to a lawsuit.

That was an idea that County Attorney Paul Sunderland sought to put to rest.

“The government is allowed to regulate land use and has a pretty free hand to do so,” Sunderland said. He said that for a property owner to demonstrate an unlawful “taking” of his property rights “you have to deny virtually all use of the property.”

“There is no taking issue here,” Sunderland said. “These regulations are eminently justifiable.”