My home, my castle: Living room renovation - update #5

Whereas many homes have a single layer of plywood, OSB, or planks, my builder saved a couple of bucks and used 1/2" particle board over 1/2" OSB. Because I'm going to be nailing down bamboo flooring and because the particle board is warped (it absorbs moisture & then expands), doesn't hold nails, and generally sucks, it was removed.

The original flooring was nailed down, so I walked the floor to locate squeaks and then used about 4 pounds of 1-5/8" decking screws to secure the OSB to the joists. Voilà, no more squeaks!

An uninsulated two-car garage is under this room, so I decided to put a layer of 15# roofing felt over the OSB (I glued and hammer-stapled the felt down). For the top layer of subfloor I could have installed 1/2" OSB on top of the bottom layer, but I prefer plywood. I "glued and screwed" 15/32" Plytanium plywood as the top layer using 2-1/2" deck screws.

To be sure my screws were finding their way into joists, I located the first one by measuring approximately 16" from the outer wall (my joists are 16" on center) and then drilled using a 1/8" bit. When my first attempt didn't "feel" like I was hitting solid wood all of the way through, I moved 1/2" closer to the outer wall and drilled again... that one hit the joist. I then marked off every 16" from that point across the floor and drilled to confirm I was hitting a joist. I repeated this process on the opposite wall and then struck a chalk line (seen in red in the photo) to mark where the joists were across the floor, which made the process of screwing down the floors much faster.

Next up is to hammer-staple 30# roofing felt over the top of this plywood and begin installing the bamboo flooring!