timber stud or metal stud (thin rails like placostil)?

Well the question is in the title... Now why this question? Here we go... In his book p.62, Rod states: "Light gauge steel framing has an advantage over wood framing or heavy gauge steel framing because a wall constructed with it has a greater STC rating than a similar wood or similar wood or heavy gauge frame". Then in John's recording manual: "substituting timber studs for steel studs generally results in a significant decrease in sound isolation" Those two statements seem to contradict each other. Not trying to stir shit here, just trying to establish what is best for minimum transmission loss. Or maybe there's something I don't get and there's no contradiction? Anyway could you shed some light on that topic, ta very much!

Rod's statement is correct. I never understood why in Europe it is standard to work with light gauge metal studs, which is better for sound isolation, while in the States they use wood causing more explicit structural resonance and limitations. As per Rod this is because wood is cheaper and more common in the states than these metal studs, argument which isn't valid here. These comments are mainly valid when the gypsum boards are screwed directly to the studs (in both cases). A difference is also if you work with wood it's easier to build stable structures with e.g. roofs. These lightweight metal studs are more meant to span a certain height (depending on size) between a stable floor and ceiling. As a general comment, for steel studs as standard used here, John's comment on that page is wrong.

Those two statements seem to contradict each other.

Actually, they don't contradict each other at all. they both say the same thing: Metal studs give you better isolation than wood studs. What John says is that if you SUBSTITUTE wood for steel (ie, instead of using steel you use wood), then your isolation goes DOWN, ie, the wall does not isolate so well. John's statement agrees with Rod's.

"substituting timber studs for steel studs generally results in a significant decrease in sound isolation"

That is exactly the same as what Rod says: Steel is better than timber. John just says it the other way around: Wood is worse than steel. - Stuart -

Stuart, I read it exactly as the OP. Further if it gives a significant decrease (as noted there), I wonder why all further construction drawings and descriptions refer to wood without any side comment that this significant decrease is accepted in function of whatever mechanical or constructional need. If it's meant otherwise I think it can better be formulated in a different manner.

French, 1st you have to keep this in perspective - my statement (and I believe it was clear) is that this condition is comparing a single line of wood studs with drywall each face to a single line of light guage steel studs with drywall on each face........ I presented nothing to compare this to staggered stud or double wall construction. Now: John said: "substituting timber studs for steel studs generally results in a significant decrease in sound isolation."...... read it carefully - it says the same thing I said in my book - there is no difference...... he is saying that you generally get less isolation with wood than with steel........ Now - that having been cleared up - this really is the general case where the drywall is nailed to each face of a single frame wall - the comparison is wood frame versus light guage steel - and in these caes - the steel will usually produce result that you can only get with wood by adding resilient channel. And this is important more in the frequency range of STC ratings (the range of the human voice) than when it comes to music and lower frequency tones....... But - if you're dealing with double wall assemblies - room within a room (if you will) you'll get better results generally with wood than with light guage steel framing - especially in the lower frequencies - this for a number of reasons....... the most important of (in my opinion) being that both sides of a light guage wall end up having to be tied together (at the very least in mid span of the wall height) by braces that join the 2 walls together - thus creating a flanking path between the 2 at that bridge. If you study IR-761 you-ll see that you can get better results with double wall 2x6 frame (at 2' on center) and only 3 layers total of 5/8" drywall - than you can with a comperable light guage steel wall with 4 layers total of 5/8" drywall. Rod

Eric, Stuart and Rod thank you very much for helping. Eric, I too am a francophone and although I only just moved back to France after spending most of my adult life in English speaking countries I still make mistakes and that was one of them: understanding "substituting timber studs for steel studs" as "replacing timber studs with steel studs" when it actually means the opposite... So, sincere apologies for the confusion! Having said that we now have the lowdown of it so thank you very much to Eric and Rod. Rod, I plan on building the inside walls with (from inside the studio): acoustic treatment-Fermacell-GG-Fermacell-Placostil-80mm Rockwool 50kg/m3, not touching the outside walls, as a stand-alone structure including ceiling resting on those four inside walls and then, as outside walls (from outside): this type of bricks below (100mm thick, performances HERE)/80mm Rockwool 50kg/m3 so that producers/hangers on etc can have a lot of fun in the chillout room while people can actually work inside the booth and the control room... So, do you still think that as I plan on building room within room I should go for timber as you indicate at the end of your post or that because of the specifications of my build light gauge steel is better? (BTW for those who don't know Fermacell is like plaster board/gypsum board but much denser)

boing?

I begun to build my walls in November. Here in France steel studs 90 were cheaper, in December it was the same price, since january wood 80X38 is cheaper

Thanks for sharing Garlo -price is of course a factor but the isolation is more important for me. From what I've read I'll go with fermacell/GG/fermacell/placostil+Rockwool, 10cm air gap, Rockwool/15cm hollow bricks filled with sand. Although there's one thing I don't really get, which is the 'sound doesn't like to go through different medium so it's better to have different medium' argument, which seems to contradict the 'mass is mass' statement. Is there something I don't get?

Actually it's something pretty simple - and really not generally a problem...... Materials - assemblies, have a relatively sharp dip due to the effect you are referring to - which is known as coincidence. The frequency of Coincidence in a wall / floor asembly is dependent on the actuall assembly itself - but in frame walls with multiple layers of dywall - it is usually found in the range if 2 ti 4 K, (2,000 Hz TO 4,000 Hz) The dip can be fairly substantial - BUT - we already have a very healthy dose of isolation in this frequency range - so a dip of 10 or even 20 dB doesn't affect us alll ths much. The MSM you refer to is really what we need to deal with the lower frequencies - and this is always the problem area. Rod

Very kind of you sir. After having read respective weight data on hollow brick and concrete block (breeze block in UK, parpaing in France...) I'm going to go for the later one - it weights about a third more, will fit it upside down (with the holes on top) and fill the holes with sand. That being for the outside walls, the inside walls being as described before. Should stop those producers' laughs (while play table tennis, pinball machine or table football from entering the working area (that, and my suppadoors of course, as described HERE)!