What a fantastic site! I have two questions:
1) What does a hardwood transition look like going from a north-to-south room to an east-to-west room? The doorway does not have a door (altho I will install a "sliding barn-door" instead of a pocket door). Do I use a transition strip or just do super-fabulous cuts and butt it up?

2) The east-to-west room has a fireplace at the east end. . .the end that we are installing a 14' x 13' riser about 8" tall. On a 80-year-old concrete floor in good shape. On the west 'lower" end I think this is the proper layering:

hardwood floor
1" OSB subfloor (too much? should I use 5/8" or 3/4"?)
barrier
original concrete

Am I right? What about the riser end? Is this the correct layering:

hardwood floor
1" OSB subfloor (too much? should I use 5/8" or 3/4"?)
riser built with kiln-dried 2" x 4" s
barrier
original concrete

The concrete appears to be flat, but putting a riser on only-barrier-covered-concrete seems odd...like I need to put something else there for absorbtion/softness? Like leave the old foam pad from the carpet we ripped up tonight?

Also, we are using 5" engineered hickory (hand-scraped) Essense flooring. The "male" part of the floorboards is only about 3/16". . . can i really use one of those pneumatic nail guns on that skinny 3/16" strip? Seems like the videos on these sites show a wider male piece, which confuses me (is this a floating floor that requires no nailing?). I have no instructions except for this site (which I have been reading for the past three hours) and the DIY Network site. MANY THANKS for your valuable time. REALLY!