"We installed hardwood over existing hardwood going in the same direction - although there was no subfloor, so pulling it up wasnt really an option. No problems at all." You had no subfloor? The hardwood was nailed every 16" directly to the joists? Did you do the work or did some contractor convince you that this was the situation? I Have not seen that in 40 years of remodeling old homes and will probably never see it. As I said before, TAKE UP THE OLD FLOOR!

Yes, it does look like an easy method to install flooring. I'm surprised to see maybe even ceramic. Not too sure about that one. It runs $2/sf. In this case it would save quite a bit of labor just on floor prep. There's adhesive on the slab which would otherwise need to be removed. It also provides a moisture barrier so he said solid wood could be used. I believe he even said 3/4 inch. Looking at the installation instructions, it looks to lay loose on the slab. I wonder what it's like to walk on one of these floors. If it feels like a regular wood floor. Another concern I have is how easy it is to replace a board. Or if a board goes crooked while trying to install it and you're already into the adhesive stage if you're stuck with a gap. Particularly worrisome when someone else is doing the install and maybe not as picky as you'd be yourself. The site says it has a worldwide patent but the salesman said that type of product has been used in Europe for over 20 years successfully. It's only new to the US. I'm looking into floating floors due to the adhesive on the slab but don't want a fake hollow sounding floor. The flooring stores I've been to don't seem to have sample floatings installed for people to check them out.

.

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.