We have a 1980’s house and are in the process of finishing the basement. We have a fully functioning fireplace with a recently (2022) restored chimney (stainless steel sleeved) located on the first floor (main living area). We use the fireplace frequently starting in the Fall through late Spring. The foundation of the house is poured concrete.

In the basement, below the fireplace, is a ”nook.” The foundation jets out here to support (match) the fireplace. There is no ash box. There is some ”popcorny“ material. I dont really know what its for? (Heat shielding?)

Hubby wants to put a custom built bookcase/shelving unit into this space. I’m worried this area gets hot? Should we put up additional heat shielding? Maybe a metal barrier or something? We have not found any guidance in our local code. Also, our fireplace cleaning had no real feedback.

Has anyone else done this - built something combustable below a fireplace? Any feedback is appreciated.