The White House disclosed Thursday that the White House ballroom project is expected to include plans to add a second story to the West Wing colonnade, a covered walkway that connects the West Wing to the White House residence.

White House officials and the ballroom architect, Shalom Baranes, told members of the National Capital Planning Commission Thursday that adding a second story to the colonnade would help make the building more uniform with the new ballroom being built on the other side of the White House. It would also dramatically alter the iconic space outside the Oval Office. 

Baranes told the commission that the heights of the White House and ballroom "will match exactly." 

Officials shared details of President Trump's planned ballroom at a public meeting of the planning commission charged with approving it. The White House also said it was not feasible to save the building's East Wing because of structural issues, past decay and other major concerns.

White House officials offered the commission the most comprehensive explanation to date for the dramatic demolition of the East Wing in October to make way for a 90,000-square-foot ballroom. The demolition caused a public stir when it began in October with little advance notice, drawing criticism from Democrats and historic preservation groups.

White House says it was more economical to tear down East Wing than to renovate it

Josh Fisher, director of the White House Office of Administration, ticked off a list of problems in explaining why it was more economical to tear down the East Wing than to renovate it, saying that there were "significant deficiencies and overall poor structural design and construction."

"The colonnade was structurally unstable. The roof systems had exceeded their service life, and the underpinnings were not sufficient to support the necessary upgrades," Fisher told members of the National Capital Planning Commission. "In the East Wing, there was chronic water intrusion, accelerated deterioration and mold contamination. The electrical infrastructure was obsolete, deemed undersized and non-compliant with current code. Facilities were also non-compliant with both ADA and Secret Service requirements."

"Because of this and other factors, the cost analysis proved that demolition and reconstruction provided the lowest total cost ownership and most effective long-term strategy," Fisher continued.

The project will include a new visitors' entry complex, which is intended to speed access to those coming to the White House to use the new ballroom and ensures they won't have to mill around under the tents or other temporary structures that are sometimes erected for large gatherings.

Some of the 12 commission members raised concerns, particularly Commissioner Phil Mendelson, who asked if the planned size and location of the ballroom might change going forward. He was told that "anything's possible" but that the existing plans had been studied very thoroughly.

Mendelson, who also serves as chairman of the D.C. Council, then asked if the planned ceiling height of 38 to 40 feet (11.5 to 12 meters) could still be lowered before the final structure is finished and received assurances that the number wasn't fully set. 

"It still seems to me it's overwhelming the existing building," Mendelson said.

Upon its completion, the ballroom is expected to be larger than the rest of the existing White House. Will Scharf, a top White House aide who has been tapped by Mr. Trump to head the commission, seemed to listen to the questions and concerns Mendelson raised. 

Mendelson also asked why the project hadn't been presented in its entirety to the commission before demolition of the East Wing began. Fisher said some things about the ballroom's construction were of a "top secret nature." Scharf repeated his past assertions that the planning commission doesn't usually have jurisdiction over site work and demolition on any project, including those at the White House.

He pointed to recent work at the Smithsonian's National Air and Space Museum, which he said was an example of demolition beginning before the commission fully approved plans.

Ballroom has prompted "agitation" from some quarters, White House acknowleges

Scharf acknowledged that the ballroom project had prompted "agitation" from some quarters, saying it had sparked "passionate comments on both sides" while also noting that public comment wouldn't be part of Thursday's session.

But commissioners were allowed to ask questions and give feedback, with a more formal review expected in the spring that would include public testimony and votes. The commission's next meeting is Feb. 5.

After commissioner questions, Scharf defended the project, arguing that the White House needed a larger and more elegant space to hold visitors. He recalled visiting Windsor Castle last year with Mr. Trump, and noted that the president would eventually be hosting King Charles III of Great Britain. 

"More likely than not, he will be hosted in a tent on the south lawn with porta-potties," Scharf said.

Speaking to reporters after the meeting, Scharf said, "Our concern is not so much about whether a ballroom is a good idea or not. I obviously believe that it is."

"Our concerns are how will that impact the public viewing experience, the visitor experience," he said. "How will this new building interact with the other existing buildings in the area and more broadly in the city."

The White House in December submitted its ballroom plans to the commission, which is one of two federal panels that review construction on federal land — usually before ground is broken. 

The National Trust for Historic Preservation has sued to halt construction of the $400 million ballroom, accusing the Trump administration of violating federal laws by proceeding before submitting the project for the independent reviews, congressional approval and public comment.

A summary on the commission's website said the purpose of the project is to "establish a permanent, secure event space within the White House grounds" that provides increased capacity for official state functions, eliminates reliance on temporary tents and support facilities, and "protects the historic integrity and cultural landscape of the White House and its grounds."

A comprehensive design plan for the White House prepared in 2000 identified the "need for expanded event space to address growing visitor demand and provide a venue suitable for significant events," the summary said. And it said successive administrations had "recognized this need as an ongoing priority."

Mr. Trump has been talking about building a White House ballroom for years. Last July, the White House announced a 90,000-square-foot (8,400-square-meter) space would be built on the east side of the complex to accommodate 650 seated guests at a then-estimated cost of $200 million. Trump has said it will be paid for with private donations, including from him.

But he later increased the ballroom's capacity to 999 people and by October, had demolished the two-story East Wing of the White House to build it there. In December, he raised the price tag for the project to $400 million — twice the original estimate.

The White House has announced few other details about the project but has said it would be completed before Mr. Trump's term ends in January 2029. The president has said the ballroom will be big enough for future presidential inaugurations to be held there and has also said it will have security features, such as bulletproof glass.

While he was in Florida last week, the president bought marble and onyx for the ballroom "at his own expense," the White House said. The cost was not disclosed.

Joe Walsh, Sophia Vlahakis contributed to this report.