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What material is best for soundproofing between basement and first floor?

happyface123 | Posted in General Questions on

i am building a 2 family home and contractor gives me the following choices:
what is the best option for soundproofing between basement ceiling and first
floor- separate apartments?

1. Thermafiber 3”with R-19
2. R-30
3. green glue + 2 layers 5/8 with channel and includes extra 1/4 inch
4. Sheetrock/Sound Basement Soundboard and 2 layers 5/8 with channel

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  1. user-6603341 | | #1

    I am curios to get an answer about this as well. I also constructing a two family home (side by side).

  2. GBA Editor
    Martin Holladay | | #2

    Happy Face,
    It's hard to understand the options you have listed. Here's the basic story: Sound transmission through floor assemblies is rated by an STC number, and different assemblies have different ratings.

    You'll have to ask your contractor to tell you the STC ratings of the various options, so you can choose the option with the best rating. If your contractor knows what he or she is doing, he's looked up the STC numbers of the options he is suggesting.

    STC ratings can be found in various publications; here is a link to one such publication:

    I have reproduced an illustration from that document below, showing assemblies with STC ratings ranging from 47 to 62. A higher number is more soundproof than a lower number.

    Here is a link to a GBA article discussing acoustics: How to Keep the Noise Down.


  3. GBA Editor
    Martin Holladay | | #3

    Happy Face,
    Here are more examples of floor assemblies and their STC ratings. Click on an image to enlarge it.


  4. Stockwell | | #4

    Green Glue has a wide variety of wall combinations and test reports on their site. I built my theater with greenglue and double 5/8" drywall screwed into channel suspended on rubber-bushing clips. I also added R-30 fiberglass into the ceiling above. It works extremely well except for the very deepest of bass which is almost impossible to contain in residential situations.

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