Holding a sponsor accountable for construction defects, of course, is not easy. Sponsors frequently use limited liability corporations that dissolve after all units sell, making it difficult — but not impossible — to hold anyone personally liable or find assets to seize. The window for litigation for condo boards is also narrow and closes relatively fast, even though some defects may take time to manifest.

Boards have different legal strategies available to them. They can sue for breach of contract or certain types of fraud, and even negligence. The statute of limitations for negligence suits is three years. For breach of contract, it is six years.

Litigation can carry a stigma. Buyers are often reluctant to bid on an apartment in a condo that has been labeled defective — and with good reason. Banks will rarely refinance a loan or lend to a buyer in a building with ongoing litigation. Legal fees and repair costs pile up. Owners, meanwhile, fear property values will plunge if word gets out that their building has defects. “There is this dark cloud that is hanging over the building,” Mr. Braverman said. “They get blacklisted.”

At 550 Grand Street, a small condo conversion in Williamsburg, Brooklyn, with persistent water problems, no units have resold since it opened in 2009. “Who wants to buy into a lawsuit?” said Naomi Azuma, the president of the condo board.

Sales have not suffered, however, at 500 Fourth Avenue. Buyers looking for new condo construction in the area do not have many units to choose from and the building has a property tax abatement, which might make the temporary assessment more palatable.

In the 20 months since the city issued a partial vacate order, 20 units have sold, according to StreetEasy.com — nearly all for a profit. When the Kaths listed their apartment last October, they said, they received about five offers in a week, selling the studio for 6 percent over asking price. The balcony issues were mentioned at the open house, and the assessment was disclosed during the contract process, yet the buyers were not dissuaded. Last month, the Kaths moved into a two-bedroom rental nearby in anticipation of the birth of their first child, who is due in April.