I'm planning on replacing my hardwood floors but I don't know if my current floors are glued down, floating, or nailed. Is there a way to find out before starting? This is on the second floor, so the base is wood. The same hardwood is installed on the first floor with a concrete slab.
There are a few ways to check this out. Like Michael stated above, a register is a good place to start. You can also look for a short piece of base board and remove it and check to see if the floor lifts up. Check any thresholds or transition pieces because many snap into a track and can be easily removed.
You can't nail hardwood floor to concrete. So, If same hardwood floor is installed on concrete slab in first floor then most probably it is either glue down or floating floor.
Is your decision to replace floor is final or depends on what type of floor you currently have ? If it is final then You can cut it in corner and check.