I have an old house and I'm slowly working on finishing the basement. The problem is the bottom two steps in the basement are poured concrete. It actually works out, that if I lay a wood tread on top of the concrete treads, that the height for my new stairway will work out perfectly.

The question is how can I go about attaching an untreated wood stair tread to a cement tread? I know untreated wood isn't supposed to come into direct contact with wood. Can I coat the cement with something? What about applying something to the back side of the wood tread to "treat" it? I have also wondered about maybe using tar paper or something between the two, but that might bring up an issue when I go to attach the wood tread.

My last resort is to simply try to break out the cement steps, but that really is a last resort.... I have also thought about buying 2"x10" treated lumber and planing it down to 1" thick and using that for my tread, but wonder how "funny" that might look stained....