This floor was glued straight on concrete. With a moisture barrier membrane painted on first. One of the things to remember when getting or laying a parquetry floor is the light coulored pieces are usually s lot softer than the darker coloured timber pieces. So either sort them out and don't use them or don't group them together. As well as don't use them in the high trafficed areas as entrance and kitchen or where you have furniturues that you move a lot as in a dining area etc. It's unfortually a lot easier that those light coloured pieces will be hollowed out more and leave a dip after the sanding, as they are so much softer. So if you can aford it try to not use them, or use them more at the edges of the rooms.