Some questions on wood floor underlayment, etc.

[mrcaptainbob]

Not sure about the underlayment portion, but as for the laying together of those pine boards.....I'd use a biscuit joiner and biscuit them every six inches. There are hammer operated nailers for setting flooring that drives the nails at an angle into the edge of the boards so they're hidden. After you set the first board down with that nailer, do the biscuits in between the nails. Apply your wood glue and set the next piece in place. It sounds like that floor will look great, and should stand up to wear for a long time!

[Ellis]

Hi,
I'm going to put down a pine floor in my entry room. I've pulled the carpet and all the old layers that were under that (partical board, linoleum, plywood, two more layers of linoleum, and a layer of newspaper from 1915(!)).
I'd like to put a layer of backerboard such as HardiBacker to bring the floor level back up close to where the carpet was. Should there be a layer of something else between the sub-floor and the backerboard? I've heard of people using tar paper, resin (rosin?) paper, or roofing felt. What do people recommend? Also, should there be a similar layer of some sort of paper material between the pine boards and the backerboard?
Lastly, the pine boards I'm using are salvaged high-school gymnasium bleacher boards. They're 3/4" thick, 7 1/2" wide, and between 14' and 18' long. They are not t&g. I suppose i could route a notch in the sides so that they overlap a 1/2" or so if it was really important. Otherwise I'll just leave the edges of boards straight. I'm thinking that I'll just use screws to fasten the boards to the sub-floor, going from one side of the rom to the other, laying each board and fastening them one at a time. Any general advise or warnings here?
Thanks for any help.