Aliza Frank and her husband, Erik, share a three-bedroom apartment in Stuyvesant Town with their four children, all under the age of 6. Fitting everyone in, along with their clothes, toys, books, furniture and other possessions, is no small feat.

“We’re always changing something,” she said. “In order to get the rooms right, we’ll have something for a minute, and then we will sell it or donate it and try something else.”

Since her youngest was born nine months ago, Ms. Frank has been using a part of the apartment that she had previously overlooked: the ceiling.

She installed a hanging chair in the children’s bedroom to add a place for them to play. “It looks like a bean bag,” she said. “It’s a floating thing that won’t take up the floor space.”