Q: The air-conditioners in our co-op building are installed in sleeves in the wall beneath windows. The sleeve in my apartment was rotted and needed to be replaced. The board decided that it was my responsibility. Is this correct?

A: “Lior Aldad, a Manhattan co-op and condominium lawyer, said that according to most proprietary leases, the equipment, fixtures and appliances installed by the shareholders should be maintained and repaired by the shareholders; walls and window frames, meanwhile, are the co-op’s responsibility.

“Although air-conditioning wall units are typically installed inside metal sleeves that are secured to the building’s wall,” Mr. Aldad said, “it is not always clear whether the sleeve itself is part of the structure.” So unless the issue is addressed in the lease, it is up to the board to determine who is responsible.