I have carpet over concrete. The concrete is all bunched in the corners and is uneven as heck. What should I get done before installing hardwood? How can I tell if the concrete is original or some recent way to cover black mastic? In the living room the concrete is similar height to adjacent terrazzo, but in the bedrooms it’s lower.

Concrete subfloors should be FLAT (not level) to 1/8th over 10 feet, 3/16ths over 10 is a lot more realistic. Get an 8-10ft straightedge and start checking in all directions. Youll spot the high and low points easily. From there its up to you to decide if spot repairs can fix the issue or if the room has to be skim-coated with self-leveller to provide a fresh starting point. Skim-coats will raise the subfloor about 1/8th of an inch so be ready for that at your door casings and adjacent tiles.

Original pour will not chip easily; if the concrete you see flakes or chips off after being hit with a hammer then its likely a self-levelling layer, put down before the carpet went in.