Soundproofing A Floor With Concrete
Jan 16, 2023You can significantly increase the isolation of your ceiling or floor by adding a layer of concrete onto either your floor of your recording studio or the floor above the ceiling of your recording studio. In this article I will explain the method for doing this and compare the STC ratings of different designs with and without concrete.
1) Using Hat Channels and IB-1 Clips to Soundproof Your Ceiling
In my studio we used IB-1 isolation clips and 7/8" furring channel attached to our ceiling joists to decouple the drywall from the outside structure. We drilled two layers of 5/8" drywall into the furring channel to isolate the ceiling from the roof above.
Below is a diagram of this design.
You can increase the sound isolation of this design by adding a layer of self leveling gypsum concrete or cellular concrete to the floor above your soundproof ceiling. This will especially help with impact noise and low frequency transmission from kick drums and bass.
2) Comparison Of Using Concrete With and Without Resilient Channel
In this diagram below from The Master Handbook Of Acoustics Sixth Edition we can see that adding a 1.5" layer of cellular concrete with a density of 105-120 lb/ft3 will increase your STC Rating and especially help in the low frequency spectrum.
For comparison, a recording studio wall can get as high as STC 63 so to keep your floor roughly in line with that wall an STC of 59 is much better than an STC of 49. Remember, any weak link in your room will compromise the STC of the entire room. So having walls with a rating of 63 is only as good as your floor, door and window STC ratings.
In this diagram we see that having access to both the ceiling below your floor and the floor above will give you the greatest isolation. If you live in an apartment with only one floor this may reduce your ability to isolate your floor and ceilings using this design.
3) Comparison Of Using Concrete vs No Concrete
In this diagram from The Master Handbook Of Acoustics we can see that when both systems are using resilient channel, but one has the concrete on the floor above the concrete floor performs better across the entire frequency spectrum.
From this diagram we can see that the resilient channel and 5/8" drywall gives you an STC of 47 while the added concrete above with the resillient channel and drywall gives you an STC of 59. Notice how you get 10db of added transmission loss at 125 Hz with the concrete. You also get 15db of added loss at 500Hz and 20db at 2KHz and above.
There is a huge benefit in adding mass to your floor above to get greater isolation.
Conclusion
First, we learned that adding mass in the form of concrete to the floor above will increase your STC ratings across the frequency spectrum. We also learned that to get the maximum isolation you ideally would have access to the floor and ceiling below. Lastly, it is important to consult with a structural engineer before adding the concrete to ensure your floor can handle the extra load.
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