What should go between a wood plank sub floor and a hardwood strip floor

Question

I am about to install a hardwood floor into a room in my 1905 farmhouse. The subfloor is 8-12" wide 1" thick planks. The floor I am installing is 2-1/4" prefinished solid hickory tongue and groove.

Reading books and web how-tos on this a few have mentioned that there should be a layer of "Construction Paper" between the subfloor and the floor strips. The accompanying pictures show stuff that is brown, paperlike and comes in 3' or 4' rolls. I have never seen the like for sale in my local home improvement stores.

What is this "Construction paper"? and is it really necessary?

Answer 1

It's also known as rosin paper:

Its main purpose is to stop air leaking through cracks in the subfloor and floor which is especially important if the space below the floor is unconditioned. (You'll also find claims that it prevents the floor from squeaking or muffles sound transmission through the floor.)

Answer 2

Although I am not a flooring installer or expert, what I have read and seen contradicts the answers that have been given so far. I don't want to down-vote them, because I don't feel that I am an authority on hardwood floors, but I do want to present the information that I have been given for your consideration. I think you should call a few flooring suppliers for the real skinny. They will gladly tell you how to use their products.

What I have seen when taking up oak floors is brown kraft paper - NOT rosin paper. Kraft paper is basically the cheapest general purpose rolled paper you can get. It provides a clean surface to position the boards when installing, and provides an air barrier if the space below the subfloor is not heated/conditioned. Also, I have seen NO paper - just right over the subfloor.