Concrete or wood - highest STC yield?

How thick should my walls be, should I float my floors (and if so, how), why is two leaf mass-air-mass design important, etc.

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brookster
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Concrete or wood - highest STC yield?

Post by brookster »

I'm trying to find out the difference between constuction with sandfilled concrete blocks and the usual stud wall format. There's a wealth both here and lots of other sites about stud wall constuction, but little on concrete and I was simply wondering which of the following solutions would be (with any extra advice you could give) the best solution for providing full frequency isolation.
brookster
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Post by brookster »

Also I've read that an extension to the existing wall - which mirrors the floated partition is the most effective form of attenuation. How is this achieved with concrete?

Thanks in advance all

Andy
AVare
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Post by AVare »

There is wealth of information on concrete and membrane type walls at the NRC. I don't have the URL, but you can find it here or with a search engine.

Short form, concrete walls provide much better low frequency Transmission Loss (TL).

I am not certain if it was a glitch, but all the designs you posted have more than two leafs. Anything more than two leafs actually DECREASES the sould isolation

Have fun!
brookster
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Post by brookster »

Thanks for the reply AVare, yet again you come to my rescue.

I'll be checking into the Concrete resource links later this evening so thanks for that.

RE the multiple leaf. I'm not sure if my diagrams were too clear. The two brick walls with the 1" are the existing external walls, so for room within a room construction purposes I thought this would be overlooked. The additional white layers on the stud walls are just thin covers of material to hold the batts in place (so I didn't think these would count as another leaf). In essence the construction I was looking at would be:

External Wall - 2 x 5/8 Plasterboard - 2X4 stud w/ RW3 infill - Air Gap - 2X4 stud w/RW3 infill - 2 x 5/8 plasterboard.

Should there be a gap bewteen the existing wall and the first stud construction, and if so, should this again be filled with RW3?

This is all relevant as long as I don't end up making the whole thing out of sandfilled concrete blocks of course! :D

Thanks again for your help ...

Cheers Andy
knightfly
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Post by knightfly »

Andy, if your brick double walls are hermetically sealed (both of them) then you indeed already have a 2-leaf system, albeit a questionable one (extremely narrow air gap, with no insulation in the cavity) - I don't have exact specs, but a rough # would be a bit under STC 50 - these #'s assume hermetic sealing in both brick courses, and no mortar globs shorting out between the two (not generally likely to be true) -

There's a close example of your wall (but with 2" air space here -

http://www.maconline.org/tech/materials ... sdata.html

your narrower air gap would drop this value noticeably -

If one of your brick courses has "weep holes" located along the bottom on the outside, this would lessen the isolation but also make it more beneficial to add ONE more mass leaf with attendant insulated air space between - if you examine the outside wall along the base, these holes should be evident if they exist. They are pretty common when using an outer brick wall with inner wood construction, not sure about double masonry as I've not done that.

Of the three examples you posted, the bottom one with wall resting on the floated floor will give best isolation - walls get heavy quickly, so your floor floating method would need to be beefed up around perimeters to compensate for the extra weight... Steve
brookster
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Post by brookster »

Thanks for the advice Steve,

I think it might be better to let you know what I'm aiming to do rather than just what I'm going to do.

I wish to build 3 or 4 seperate rooms contained within a larger space which is itself constructed with a brick wall perimeter as above. It is a ground floor area with a concrete floor and a concrete ceiling.

My main concern is sound isolation between the live room, vocal booth, control room and the drum room (i.e. the rooms I am looking to build as floating structures) which I wish to be kept to an absolute minimum. My secondary concern is noise escaping from the main building and noise entering it. The studio is to be situated on a busy high street.

My building skills are slightly above average, but I have good friends in many trades who are willing to help - so construction would be no probem.

My main concern with using timber stud construction is that the place I am currently is built from this to spec. Though it does a fantastic job it's still not quite as good as I'd like.

I'm moving to my new place at the end of July and I wish to be able to have a firm concrete (no pun intended) idea of how it's going to be constructed.

So my most pertinent questions would be

1. Will each room require it's very own 2 leaf system to provide adequate isolation from the next room - or would the inner leaf of the first room act as the outer leaf of the second room and vica versa?

2. Will concrete blocks (solid or filled with sand) be more suitable than stud construction, offering higher TL?

3. How do you float concrete walls independently of floated concrete floor?

4. If you have a 2 leaf system made of concrete blocks, what is used as the spring bewtween - air/air & RW3/RW3 alone?

I realise that these may not be easy questions, but I would truly appreciate your help in any way you can give it.

Thanks again

Andy
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