Hello all,

Thanks in advance to any information that may be given here. I have installed hardwoods before, but never 5". I have spoken to a few installers in the area and they tell me that they are running a bead of liquid nails or similar under the tongue of the course prior to nailing the next row. They say they are only doing this on large 5" + plank. I have never heard of this before and am not sure that I get it seeing that it is not going to adhere to the subfloor because of the 15# felt.

The question is, is this the correct method? Is it really needed. Why does it matter? I cant see that it helps buckling because it is not being glued down.

Thanks again,

I use a zig zag bead of PL Premium on plank widths 6 inches and over. It's suppose to help with stability, to keep from cupping in wider widths. Never have done this with 5" widths, and never any issues. That being said...there's nothing wrong with doing this on a 5" width.
You do away with the underlayment, and it's best to use a urethane adhesive recommended for flooring, ( not just any old PL or Liquid Nails).

I would glue down anything over 4 inch and sometimes will even glue 4 inch if I feel that the house isn't well climate controlled.And as mentioned, you do not use underlayment, you glue the flooring directly to the sub floor.The reason glue helps is because the wider the board you use, the more prone it is to cupping or crowning.

And as mentioned, a quality urethane glue like Bostich's Best or Sitka Bond is best to use.

I asked this question myself about a job I am doing with 5" Beech. I decided not to due to the difficulity in performing a repair in the future if need be. Plus mine is a floating subfloor. But this house has a HVAC system that you can set to a zone of heat and cool automatically. It's set for 69 F for heat and to AC when it reaches 75 F. So I feel the floor will be in a very stabilized climate.