Forgot all about this. I was helping a friend a few years ago. Lucky guy works at a lumber yard and knows how to use tools.
He had a 3 car garage. Concrete floor. Concrete exterior with 2 x 4’s. He wanted to save the look of the home - so we kept the garage door cosmetics on the outside when reframing, insulating and building out the walls.
The fun part was building a number of bass traps. Thankfully the ceiling was not 8’. There was a bump at around 65 hz. Pretty normal, right? It also had nasty mid-bass issues from about 115 and 500 hz.
The room ended up pretty nice. If you can get materials for free - this is a fun project! He probably saved about $10K.