A plan to increase the overall height of the fence surrounding the White House by approximately 6 feet, about doubling its current height, won preliminary approval from a Washington arts commission Thursday.

The move follows high-profile security breaches at the executive mansion over the past two years. The U.S. Commission of Fine Arts gave its concept approval Thursday to the new design, which also includes thicker and stronger metal fence pickets. The new design still must be reviewed by a second commission, the National Capital Planning Commission. The final design also must win approval from both commissions.

Secret Service and National Park Service officials said in a statement that they hope to begin constructing the new fence by 2018.

The plans follow several fence breaches. In September 2014, a Texas man, Omar Gonzalez, managed to scale the fence, enter the executive mansion and run deep into the building. Gonzalez, who was found to be carrying a folding knife, was ultimately sentenced to 17 months in prison. The security breach prompted officials to put up a second, shorter barrier several feet in front of the fence and to restrict people from entering the space in between the two barriers. Signs tell visitors: "Restricted area" and "Do not enter." The Secret Service polices the area.

A month after Gonzalez was arrested, another man also got over the fence. In 2015 a second layer of steel spikes was added atop the fence, but a college student draped in an American flag got over the fence later in the year.

The new design raises the steel fence's height from 6 feet to 11 feet 7 inches. The fence will be even taller still because it currently sits on a stone base that is 1 to 2 feet depending on the slope of the ground. The base of the new proposed fence would be 6 inches higher.

Officials have compared the height of the White House fence to other fences at buildings in the United States and abroad. A fence around the parliament building in Brussels totals approximately 13 feet while the fence around London's Buckingham Palace is about 11 ½. The height of a fence at Mississippi's governor's mansion totals 12 ½ feet and the height of a fence at Drumthwacket, the official residence of New Jersey's governor, is 7 feet tall.

The White House fence proposal is expected to go before the National Capital Planning Commission this summer. Officials will then refine plans and return to both the arts and planning commissions for final approval in the winter, said National Park Service spokeswoman Jenny Anzelmo-Sarles. Officials have not said what the fence is expected to cost.

Thomas Luebke, secretary of the U.S. Commission of Fine Arts, says commission members are interested in seeing a mock-up of the fence before giving final approval. They want to make sure that the proportion, scale, details and color of the fence work, he said.

"It's a big change. There's no question about it," Luebke said.