Can nail down hardwood but upto fireplace?

[stoneman]

I know there has to be an expansion gap around the perimeter of the room when installing naildown hardwood but is it okay for me to butt it right upto my fireplace?
Also would it be okay to butt it up to the front entrance of the doorway in my house or do i have to leave a gap and use quarter round?

[Floorguy]

Undercut the fireplace hearth, or use an endcap molding. @ the door, an endcap molding works good, too.

[Al Gladden]

i normally use 3/4 oak shoemold across doorways. but undercutting a fire place to me is the only way to go..