Wall construction

[Bergz]

Hi!

I have a little freestanding wood house/storeroom (3x6 meters) in the garden that I want to rebuild to a studio. I need it to be much more soundproof than it is now because there goes a train every 30 minute 100 meters away, plus that I do not want to disturb the neighbours (3 meters away).

I have seen many examples of how to soundproof walls and with STC measurement, but then there is drywalls on both sides (or concrete on the outside). But here is the exterior wall wood paneling.
So from the outside and in there is:
1. Wood panel (1,2 cm)
2. Windstopper
3. Fiber insulation between wood studs (2x4)
I have removed he inner wall that was a thin wood panel to get a layer of drywall or two with green glue, or even add some more insulation and maybe some furring channels too.
So now it’s like Fig.1

Fig-1.jpg

So what should I do next to get it soundproof enough (STC 55-60)?
Are some of my examples good enough (see pictures) or should I do it other ways?
Things like the door and the floor is under control.

Example 1 and 2 (FIG.2 and 3):

Fig-2 and 3.jpg

Fig.2: Mounted clips and furring channels with two layers of drywall with greenglue additionally to fig.1.
Fig.3: Mounted an another layer of fiber insulation with wood studs (2x4) and then with clips and furring channels with two layers of drywall with greenglue additionally to fig.1.

Example 3 (FIG.4):

Fig-4.jpg

Fig.4: This is almost the same as fig.3 but with one layer or two of drywall between the two layers of insulation and wood studs. But this will may cause the “triple leaf-effect”?

As I said, I have seen many examples of how to soundproof walls and with STC measurement, but then there is drywalls on both sides (or concrete on the outside). Here is the exterior wall wood paneling, so how much will that differs?
I hope for good advices on how to do it the best way.

Thanks

[Soundman2020]

Hi "Bergz", and welcome!

there goes a train every 30 minute 100 meters away,

You might need more than just isolating your walls. Trains often cause vibrations in the ground itself, which will come up through your floor. You might need to isolate your floor as well, and that isn't easy.

Test your floor by feeling for vibrations with your fingertips when a train is going past, or even better, borrow a stethoscope from a doctor friend or nurse friend, and use that to listen the floor. If you hear or feel vibrations in the floor, then you have a problem.

So from the outside and in there is:
1. Wood panel (1,2 cm)
2. Windstopper
3. Fiber insulation between wood studs (2x4)

1. What type of wood paneling is on the outside? Is that individual planks with gaps between, such as wood siding? Or is it large solid sheets of wood, such as plywood or OSB? A photo would be good...

2. For "windstopper", I'm not sure if you are referring to an air barrier, or a vapor barrier, or a moisture barrier. Then can look very similar, but they are very different. You will need to identify what it really is.

3. What type of fibrous insulation is that? Is it fiberglass, mineral wool, cellulose, styrofoam, or something else? How thick?

So what should I do next to get it soundproof enough (STC 55-60)?

STC is not a good system for measuring studio isolation. STC does not consider the bottom two and a half octaves of the spectrum, and it does not consider the top two and a half octaves of the spectrum! It only considers a small band of frequencies in the middle of the spectrum, that roughly correspond to human voice frequencies and typical home and office noise frequencies. This is what the actual STC specification says:

ASTM E 413 – 04
Classification for Rating Sound Insulation

4. Significance and Use
4.1 These single-number ratings correlate in a general way with subjective impressions of sound transmission for speech, radio, television, and similar sources of noise in offices and buildings. This classification method is not appropriate for sound sources with spectra significantly different from those sources listed above. Such sources include machinery, industrial processes, bowling allies, power transformers, musical instruments, many music systems, and transportation noises such as motor vehicles, aircraft and trains. For these sources, accurate assessment of sound transmission requires a detailed analysis in frequency bands.

Note what it says about music sources and trains...

So you should not be looking at STC ratings for your studio. Instead, you should be looking at "TL" or "Transmission Loss", and specifically you should look at the full transmission loss graphs, not just a single number.

Anyway, your "Fig 2" would not give you much extra isolation. Your total isolation would be around 35 dB, or maybe a bit more. Furring channel does not decouple the drywall from the studs. If you were to put RSIC clips in there, alone with hat channel, then that would help: you could probably get 45 dB of isolation like that. You could get something similar if you used resilient channel, instead of furring channel.

"Fig 3" is absolutely your best, but you do not need the furring channel with that one. Just attach the drywall directly to the studs.

"Fig 4" would be pretty bad: maybe 30 dB or so. It is a fully coupled 3-leaf system, so isolation would not be good, especially in low frequencies.

As I said, I have seen many examples of how to soundproof walls and with STC measurement, but then there is drywalls on both sides (or concrete on the outside). Here is the exterior wall wood paneling, so how much will that differs?

For all of the above, I am assuming that your external wood paneling is something like plywood or OSB, that is correctly installed, well sealed, and with no major changes in surface density. If that is not the case, then the above does not apply. If your external wood is just wood planks, then the above is not correct. In that case, the isolation would be much less, in all of the scenarios.


- Stuart -

[Bergz]

Thanks for the reply Stuart

1. The Wood paneling is individual planks as wood siding, but they are pressed together, so they're sitting pretty tight.
2. When I say "windstopper" I mean air barrier. (Suchs as vapor barrier or moisture barrier will be on the inside of the insulation.)
3. The insulation is Rockwool (Flexi A) 4 inches. This is the standard we use in Norway for best sound isolation.

The furring channel in the examples are mounted on/with clips, so they will decouple the drywall from the studs.

Why I thought of the fig.4 could be good was that the Extra drywall would substitute the wood siding, but as you say it will probably get things worse like a triple leaf effect. But I guess this would be the best result /see the drawing) (or do you have a better idea?).
That will be the same as fig.3 but I will take down the wood siding from the outside and put up a drywall on the excisting studs (from the outside), then put a wooden strip for airing between the drywall (this air will not cause a cavity because it will be open under so air can come bestween the walls) and then put the wood siding for å pretty finish:

Wall.jpg

But if I do not want to remove the exixting wood siding, do you have a good idea of how to get a good result?

Regards Bergz

[Soundman2020]

1. The Wood paneling is individual planks as wood siding, but they are pressed together, so they're sitting pretty tight.

OK, but are they sealed air-tight? Unless all the gaps are totally sealed, hermetically, you won't have good isolation.

3. The insulation is Rockwool (Flexi A) 4 inches. This is the standard we use in Norway for best sound isolation.

OK, that will be fine.

The furring channel in the examples are mounted on/with clips, so they will decouple the drywall from the studs.

What type of clips?

(this air will not cause a cavity because it will be open under so air can come bestween the walls)

It is still a leaf, and there will still be resonance. The cavity does not need to be sealed in order to create a resonant system. It is more efficient if it is sealed, yes, but it still works with holes in it. Think of this: if you cut a holw in the front head of a kick drum, does it still "boom"? Yep. If you take the bottom head off a floor tom, does it still sound like a floor tom? Yep. So in your suggestion, you still have a 3-leaf system, and since the air gap is very small, the resonant frequency will be very high, which means you wont have much isolation...

But if I do not want to remove the exixting wood siding, do you have a good idea of how to get a good result?

The normal way of doing that is to add the mass from the other side of the wall: on the inside, between the studs. Take out the Rockwool, seal all the joints in the planks with acoustic caulk, cut strips of 16mm drywall to fit in between each stud bay, and push them up against the planks. Seal around the edges with caulk, then add cleats to hold the drywall in place. then put the insulation back, and build your inner-leaf.

For the inner leaf, you do not need the clips and hat channel: The independent stud frame already decouples the wall completely, so it is no use to decoupled it again. you don't gain anything extra like that. Resilient mounts are only needed when there is only one stud frame, but if you have two stud frames (as in your drawing), then you don't need them.

- Stuart -

[Bergz]

Thanks again Stuart, this was very informative

The clips Are called "Dreamscreen Prosilence clip for wall and ceiling detachment" and are used by cinemas and music studios.

The best way to get this "house" soundproof is probably the way you explains it, to put drywalls between the studs and seal around. But what about this "airing" thing all the carpenters are talking about here in Norway between the exterior wall and the insulation. I think it's because of the cold winters here, and when it's hot inside. Therefore we also must have this type of vapor/moisture barrier on the inside of the insulation. Do you know something about that?


Thanks again

Bergz

[Soundman2020]

The clips Are called "Dreamscreen Prosilence clip ..."

OK, those look fine. But you don't need them!

The best way to get this "house" soundproof is probably the way you explains it, to put drywalls between the studs and seal around. But what about this "airing" thing all the carpenters are talking about here in Norway between the exterior wall and the insulation.

That is necessary if you have "leaky" external siding, where air and moisture can get through to the wall interior. If you correctly seal your outer layer, and there is a air and water barrier under it, then you would not need that. Right now, you don't have that anyway! If you are concerned about this, then check with a local expert (not just a carpenter: an actual architect) and also with your local building code, to find out what is acceptable, and why. Also, if there is any doubt at all about air or water penetration into the cavity, then do not use drywall for this: use marine grade plywood instead. And for extra safety, use Green Glue in between the sealed siding and the plywood.

Therefore we also must have this type of vapor/moisture barrier on the inside of the insulation. Do you know something about that?

That's the vapor barrier, and it always goes on the warmer side of the cavity, up against the inner-leaf. People often get confused about water barriers, air barriers and vapor barriers, but they are not the same thing.

But check with a local expert on building construction, explain what you need to do (add mass to the outer leaf without adding air gaps), and find out what the locally approved method is for doing that.


- Stuart -

[Bergz]

Thanks a lot Stuart!
I will check out the building construction with a local expert as you recommend.
I know at least what I have to do to get it as soundproof as possible, thanks to you

Bergz