In regards to using OSB, I have the following comment: I am a structural engineer in California, and I have specified OSB as a subfloor, roof sheathing & shear wall sheathing for hundreds of homes. As far as an underlayment for hardwood floors, there appears to be two issues. 1) is the floor structurally sound for hardwood, and 2) whether attaching the hardwood directly to OSB will result in nail slippage many years down the road. I have comments on both issues. As far as the floor being structurally sound, I have seen a few posts on this issue & I am not one to automatically say that hardwood should be placed perpendicular to the floor joists... But it would definitely be stronger and may help in easily repairing the hardwood attachment if the nails should slip many years down the road. I myself have placed the hardwood parallel to the floor joist because my subfloor is very stiff. To get a stiff floor, this is my recommendations: joist spacing should not exceed 16"o.c.; floor joist span should be designed conservatively (building code minimum is not conservative), and floor sheathing should be 3/4" nominal and placed with the face grain (long dimension) perpendicular to the joist & staggered. In regards to item 2: some national floor associations have said direct OSB attachment is acceptable as long as sheathing is PS2 standard & 23/32" minimum. That is all we can go by. As I mentioned above, let's say the nails do slip after many years... If your hardwood is perpendicular to the joist, couldn't you just screw it down to the joist below as a repair? That is one benefit I can see with placing the hardwood perpendicular to the joist or adding blocking between the joist. In regards to nail slip, I posted a blog regarding using the hardwood nailers that drive the cleats at an angle in the tongue of the hardwood edge. The cleats are locked in place inside the T & G connection. How is this going to lift up? Also when you drive the nail at an angle, there is a vertical bearing component of the nail that is preventing the nails from lifting. This is versus using a brad nailer that goes vertical. The vertical nail would rely totally on friction between the OSB & nail and I can see this possibly slipping down the road.

Yes. I have sanded and finished subflooring for customers. Really no different from any other flooring finish work, except that you have to consider the fact that it happens to be a single construction floor system and, therefore, you have to take steps to protect what is below the floor when you sand and then apply stains and finishes. Anything you do above to the floor surface can easily find its way down to the space below...dust, stain and finish. You have to sink any top nails below the surface of the wood before you sand and continue to punch them below when necessary. You probably can never remove all tar paper lines and staining, but that is OK, as the floor will have a great look all by itself. I have finished these natural and stained a few. I also colored one green once at a customer's request. That one was unique and beautiful.

I second the suggestion for the waterhog mats. I'll post where we purchase them if I can find the link - you can get custom sizes, colors, styles, etc. LL BEAN sells them too but they are very pricey IMO. We use them around our dogs water bowls too since they are sloppy drinkers. In addition to our entry way, we also use them in the back of our SUV's in the cargo area since we travel with our Boxers. Keeps the truck nice and clean and absorbs liquids. After my dog had surgery he peed in the truck on the drive home from the vets office (post-anesthesia, if I remember correctly) and I was thankful for that waterhog mat. Not a drop of urine on my upholstery; the waterhog captured all of it, and it was easy enough to clean -- I sprayed it down with a hose and some cleaning solution, left it out to dry and no residual smell whatsoever. They're awesome mats.

To match the white oak (which they said was old red oak!) which got only one cost of stain. The living room and upstairs hall and two bedrooms have white oak. They put red oak in dining room, kitchen, pantry, powder room, side and back hallway, breakfast room, library, media room, office, laundry room, huge bathroom and master bedroom. And it's a mess, looks horrible! Our contractor says there is no chatter, no white oak, great finish and refuses to accept any opinion other than from someone he will choose to bring in! I fidget an opinion that the red oak was very low quality.