I have 1000 sf of subfloor over finished basement in a 1970s two story residence. We want to achieve maximum sound proofing on this floor with open den/living room /foyer. Unfortunately I did not add soundproofing to the basement ceiling five years ago.

We are set on using a mid range engineered 5 inch by 3/8th inch plank. We want contractor to pull up all carpet so we can address 1/2 tongue & groove subfloor and seek to treat certain squeaks and gaps and also pull up every other row and install Roksul in cavities- I think i can place /push them in.

Then we want an underlayment with best acoustic properties say ECO ULTRA 980 or Floor Muffler but this decision gets confused by literature regarding a need to glue it down with say normal glue or not. Then install wood planks with more expensive glue Roberts 1535 at say $170 for 4 gal pail. The various posts say no need to glue down underlayment all. The acoustic glue is expensive I need 5 4 gallon pails. Any experiences?

  • If your sub=floor is only 1/2 inch plywood . You need another layer of plywood . Sub- floor should be at least 3/4. Thay did that back then and you added the nest layer to what finish was going down . such as carpet in rooms 1/2 inch particle board was added. In kitchens and bath a better grade plywood was added.
    – user101687
    Jun 18 '19 at 10:52
  • I would screw the next layer down and paper between it to reduce squeaks.
    – user101687
    Jun 18 '19 at 10:57

There is no need to glue down the underlayment padding. The weight of the floor will hold it in place. If you don't want it to shift while you are installing the floor, you can use double sided tapes (like the one used for carpet) to hold it.

I usually only put few strips of tape in "tricky" areas such as when approaching a door. In a rectangular room, I don't use tape.

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