Redroze, I'm just getting back online and seeing your questions, so I'll try to answer what I can. My new floor in the LR/DR was not pre-finished, it was all site-finished. I did put a pre-finished floor down in my office (no pics, sorry) because I work from home and didn't have time to be without my office for the week it would have taken to have floor sanded etc. The pre-finished does have a different feel to it than the site-finished. I wouldn't say it's grooved, just a more defined difference in between the individual planks. The office doesn't adjoin any other room, except the tiled hallway, so I didn't worry so much about the wood being different there. I see from your pictures what you mean about running the planks the same way and wanting to be sure things don't look odd. One idea might be to take up some of your FR planks, like the first 12 or so, and then put them back down interwoven with the new planks. That way there's not a clear line in between the 2 rooms, but rather a more gradual blending. Here's another couple of pictures, this time of my family room. The first one is a before shot of the hardwood floor + a rug-like carpet. The floor created a frame around the carpet. I had the carpet taken up and new hardwood put in where the carpet originally was, then everything sanded and refinished. You absolutely can't tell where the old wood was vs where the new started. In this case, the new is random width because it opens directly to the kitchen (as opposed to the LR/DR which is all the same width). So, one house, all new site-finished floors in the LR & DR, all new pre-finished floor in the office, original/refinished in the kitchen, and half&half refinished + original in the family room. Boy did we have dust! Hope this helps! New:

The answer could be "Yes". It could be "No" or it could be "maybe...it depends". The trick with this is that new hardwood does not like sitting over top of OLD finishes...like polyurethane. And new hardwood needs FLAT. So the chances are VERY high that you need to SAND DOWN your old hardwoods (to remove the finish AND to flatten any obvious areas of concern). That should cost you $2/sf. Now the fun part...getting patch down where it is needed. It is possible but old hardwoods don't normally like to have concrete patch put down on them. They can. But they aren't fond of it. The cement patch often cracks and disintegrates as those old floors move. You will still need patch = $1/sf (on the LOW end). The other fun thing is: you probably have to install the floors perpendicular to the old floors....which will be AGAINST the installation instructions/warranty (most hardwoods must be installed perpendicular to the joists...which would be your OLD hardwoods...but the NEW one's would be perpendicular to THOSE = parallel to your joists = against all "Best Practices"). The way around this = DIAGONAL (lay it at a 45deg. angle). This should increase your WASTE into the 15% range = 15% more expensive than anticipated. So if you add up all the "trouble" you will go to, you will be paying about the same or MORE to do this. Of course you could throw down some plywood over top the old hardwood = go ahead as a normal install. But that puts you too high---so your ONE option to do this "cheaply" is not on your list. Go ahead and remove those old hardwoods (I'm assuming they are so OLD that they cannot be sanded and refinished). Lay new plywood and then install the new hardwood. The cost to do this properly should add $2-$3/sf (labour and plywood included). If you do this the "cheater" way, it should cost you $2-$6/sf (that includes the diagonal install with extra waste) and lose you your warranty. After all that money for the hardwood and install, that would be a sad state of affairs.

If it is cupping, it looks pretty slight to me. Cupping--unless it's evident shortly after installation--is usually the result of moisture imbalances which are due to environmental conditions outside the contractor's control. Cupping is more evident the wider the flooring width which is why I recommend engineered hardwood for widths greater than 3" As a point of calibration, the performance standard published in NAHB's Residential Construction Performance Guidelines for Professional Builders and Remodelers is: "Cupping or crowning in hardwood floor boards will not exceed 1 /16 inch in height in a 3-inch maximum span measured perpendicular to the long axis of the board. Cupping or crowning appearing after installation may result from fluctuations in the moisture conditions in the house, causing a noticeable curvature in the face of the floor boards. Cupping or crowning caused by exposure to moisture beyond the contractor’s control is not the contractor’s responsibility." If the OP wants to minimize cupping, they'll need to control the relative humidity in the living space as well as the space below the floor. If it's a basement or crawl space, moisture controls need to be in place and some amount of conditioning may be required.

Laying the new floor in the same direction as the old floor is not the normal way to go about this. In the building industry, it is more common to see layers that are staggered or "bricked". In other words if layer #1 is laid in a North-South direction, then layer #2 (the top layer) is laid perpendicular to it in an East-West presentation. If you want to run the new flooring in the same direction as the old, you will want to use some underlayment (plywood) over top of the old floor so that you can maintain the "staggered" or "bricked" layering system. That is one way to maintain the North-South presentation. Please work with hardwood flooring professionals who have some experience renovating these old gems. They will have seen what worked....and what didn't. Their experience will be invaluable on a project like yours.