HVAC rough-in mistakes that cause callbacks after drywall

HVAC callbacks after drywall are usually not about one big mistake. It is the little rough-in details that nobody wants to stop for: no service clearance, drain line with a bad slope, return path too tight, boot not sealed, access panel forgotten. The problem is that everything looks fine before walls close. Air still moves, the unit runs, and nobody wants to delay the schedule. Then the homeowne…