Is it ever a black & white answer? Generally, structural element especially those enclosed by walls and other finished surfaces typically fall into the responsibility of the HOA. Things may differ from common practice when you start to consider condos that include stand alone buildings or unusual classifications like 'air condos'. Some things might even be dictated by the local laws governing these types of arrangements. There may also be some precedences set by the HOA that address when homeowners cause the problem such as plumbing problems or ignoring a maintenance issue. The best advice I can give is suggesting you review the condo documents provided when you acquired the property or receive as part of the title or resale certificate documents should you currently be in the buying process. You may also want to consult a lawyer who can provide an opinion on your exact question. Good luck.