I'm laying 5/8" - 7" wide acacia engineered over a wood subfloor (nailed). Manufacturer install instructions recommend 15# roofers felt but wanted another opinion. I have go over 300sqft area where I am removing ceramic tile plus another 1200 sqft. After removing the tile there is some thinnest still on patches of the wood and although I am scraping it down pretty good there may be some uneven spots here and there. So question is would a thicker underpayment allow for some uneven areas in the floor or should I sent the extra time sanding it down?

If any recommends a thicker product can you recommend any specific ones?

Thanks

You'll want to remove as much as possible. Trying a thicker underlayment to avoid proper floor preparation is not the way to go. Possibilities that may occur include separation of the leftover thin set once the naildown procedure starts. Vibration from nailing or pounding boards into place etc. creates loose debris that could create crunchy sounds underfoot.

Proper floor preparation is always paramount.

Thanks. I plan to remove all bumps with a grinder.

Any recommendations on a underlayment. I've been told cork is preferred but its expensive, or a more economical option is foam.

Any opinions?

I was considering using this option (something between cork and foam price wise ) under 5/8" engineered.

http://t.homedepot.com/p/Roberts-3-67-f ... 202953778/