I am in the process of finishing my basement. The floor joists are used for the cold air return from the upstairs. When the house was built, the builder installed sheet metal to ceiling to create the duct. I have had to remove some of the sheet metal in order to do some electrical work. My question is, do I have to replace the sheet metal before I drywall or can I just install 1/2 inch drywall in the ceiling and still be in compliance with code. It would be nice if I don't have to replace the sheet metal since I had to bend it to get it out and I have installed some light fixtures in the ceiling joists used as the cold air return.

Joe In Idaho