The Chilmark conservation commission voted this week that a house perched precariously at the edge of a cliff overlooking Stonewall Beach cannot be moved again, and instead must come down.

“We’re at the point where this house should be removed, not relocated,” commission chairman Pamela Goff said. “This [application] is just delaying the ultimate end.”

Chilmark town leaders agreed that the decision marks the first time in memory that a house will be demolished due to the threat of erosion.

The modest summer home on Greenhouse Lane is owned by Natalie Conroy, a longtime Chilmarker whose property has been at the mercy of severe erosion in recent years as storms and heavy wave action have battered and eaten away large chunks of the south-facing shoreline. There is also a second dwelling on the property that contains a bedroom. In 2011, Mrs. Conroy moved the house back 26 feet with town approval, but has continued to lose land.

The main house now stands just eight feet from the edge of a cliff that drops sharply to a beach directly facing the Atlantic Ocean.

Mrs. Conroy had applied for permission to move the house and detached bedroom again, this time nine and a half feet back from the cliff. The moving plan would have brought the house to rest in the middle of an access road to a neighboring property and directly abutting a freshwater wetland. The plan called for elevating the house on seven-foot pilings, and for installing a new so-called tight tank for septic disposal, 10 feet away from the wetland. The move would have created 15 feet of frontage between the house and the cliff.

Until now the conservation commission has allowed a series of temporary emergency measures while Mrs. Conroy developed a plan to save the house.

But when it came to a final decision at a meeting Wednesday, the commission found the plan was inadequate and said the time had come to face reality.

“We just don’t allow houses to be built right up against the wetland, it’s derelict of our duty,” Mrs. Goff said. “We totally sympathize, but it seems like to buy a year you’re going to have this potential damage done to another resource area. It’s just pushing it past what’s reasonable.”

Mrs. Conroy now must return to the commission within 30 days with a plan to remove the structures. The main house is currently supported by a system of piers that are driven into the bank; once the face of the cliff reaches the first row piers the house must be removed.

The cliff has lost approximately 45 feet since 1997 when Mrs. Conroy purchased the property, she said.

The cliff has lost approximately 45 feet since 1997. — Ray Ewing

In September 2011, tropical storm Irene left the house within feet of the cliff’s edge and the commission issued Mrs. Conroy an emergency certificate to move the house back 26 feet.

The house was left in the same perilous position following Hurricane Sandy’s hard blow last October. Mrs. Conroy was granted 60 days to file a notice of intent to move the house and detached bedroom. A subsequent extension was granted.

But with so little back property remaining, the only option was to move the house into a road used to access a home owned by Karl Langmuir. In a letter to the commission, Mr. Langmuir said the family will “continue to consider the proposal” as they move forward with their own potential relocation “but must retain the right to access to the property at this time.”

Mrs. Conroy told the commission Wednesday she remained hopeful about the outcome. “I’m an optimist and I’d like the opportunity to see how much time we could get there,” she said. “It’s a very emotional and gut-wrenching decision to remove the house . . . this is a plan to be implemented the minute the Langmuirs say go ahead.”

But commission member Wesley Cottle said time could run out before Mrs. Conroy has Mr. Langmuir’s approval in hand.

“My problem is you have no idea when you can move the house into the road,” he said. “It’s like playing Russian roulette with the storms. You have to reach a point to make a decision.”

Mrs. Goff said the road already impedes on the wetland and moving the house could increase the disturbance.

David Michniewicz, an Orleans coastal engineer hired by Mrs. Conroy, argued there would be no impact to the wetland “even though the corner of the house is right up to the wetland . . . given the height above the wetland itself. “ He said there could be less disturbance to the wetland with the house relocated.

But commission members said nature is too unpredictable.

“The one thing that’s running through all of our minds is one storm can, and has, taken that much away,” commission member Joan Malkin said.

Commission member Chris Murphy agreed.

“It seems logical to me that this is time to take the house away — it’s time to go,” he said. “If it can move 26 feet back in one big bite, the next big bite could easily take the house . . . it doesn’t make any sense to me to continue this any further.”

In the end, commission member Candy Schroeder made the motion to deny the application and the decision was unanimous.

Mrs. Conroy said she would return to the board with a proposal to install a new aboveground tight tank to be installed under the deck. The current septic tank has been pumped and abandoned and the new tank could allow her more time in the house, possibly one more summer, she said.

The next day Mrs. Conroy admitted that the commission’s decision caught her by surprise.

“I had no idea that it would come down to the decision that it did,” she said. “On the other hand, I didn’t have a real definitive plan.”

She said her application was an attempt “to salvage what little bit of pleasure I can get out of life.”

“It’s been a wonderful opportunity for me to be able to enjoy a bit of the Vineyard,” she said. “Many, many hurricanes there, I would shutter it up and leave and say, I’ll be back after the storm.”

A structural engineering plan ruled that the house is sound, so Mrs. Conroy may continue living there for now. She said she lives in the house during the summer and has children and grandchildren visiting every weekend.

“The house is perfectly designed for the site — you have the nice solar energy without the heat,” she said. She said the house still has a wall with a list of whale sightings spotted off the beach that was there when she bought it. “It’s a terrific piece of 1950s architecture,” she said.

The lot was just over one acre when she bought it. With so much of it gone, Mrs. Conroy said she plans to file for a tax abatement with the town.

“I always said my kids would have a beach lot,” she said. “But I didn’t think it would be this soon.”