Single concrete or double layer walls?

Great Forum :) I am in the process of getting a small studio built under my brick house. It is a very small space (the control room is 3 x 4 metres, with a 2 x 1.4 metre booth.) The ceiling height will only be 1.95 metres, once the ceiling is soundproofed. If I build a typical two leaf stud/double plasterboard system wall, I worry that I will lose a lot of my limited floor space. I also worry about white ants infiltrating such a system ( I am in Brisbane, Australia.) I also worry about security. I am worried about most things:) Isn't it easy to kick in such a wall though? I guess I would prefer a one-layer concrete wall. My question is this... What is my best option in terms of materials for the walls? I want good sound proofing, but also some absorbancy so I'm not left with an impossibly reverberant space. My choices seem to be Besser block, Besser block filled with sand or aerated concrete (like Hebel block). The Besser block has an advertised STC of 50. Concrete-filled Besser block is rated 55, while cavity Hebel panels are rated at 58. The Hebel looks promising, but will still require rendering or a gyprock layer on the inside and I worry the cost will build up. Maybe I should persist with the cheap, traditional stud, two leaf gyprock system wall with rockwool in between, that everyone is so keen on in this forum. Any ideas would be hugely appreciated:) I don't want to make a costly mistake here. Thank you. Ross Mac

This is one of the dilemmas I've faced when trying to design my garage stoodio :roll: http://forum.studiotips.com/viewtopic.php?t=2203 I've thought about a large number of different designs. :idea: Here in the UK I've been told that cost wise a masonry wall and stud wall are equivalent. There is an issue, if you have a wall cavity about ensuring you do not get condensation. the following document will be useful in deciding whether to go for the complete double skinned wall or to go with a concrete wall: http://irc.nrc-cnrc.gc.ca/pubs/fulltext/ir586.pdf The NRC has quite a large number of documents that are worthwhile reading, including: http://irc.nrc-cnrc.gc.ca/pubs/fulltext/ir761/ir761.pdf Also, don't rely too much on NRC numbers. They do not take into account low frequency performance (which may be critical depending on the type of noise you're making!!) :D In particular I noticed that masonry walls with plasterboard attached by RC were not nearly as effective at low frequencies as a double masonry wall. Hope this helps

diziet wrote:

. . . don't rely too much on NRC numbers. They do not take into account low frequency performance (which may be critical depending on the type of noise you're making!!)

I think you meant to say, "Don't rely too much on STC numbers." NRC stands for National Resource Council, a Canadian organization that includes the Institute for Research in Construction (IRC). We love those guys!! 8) 8) 8) STC stands for Sound Transmission Class. That is the extremely flawed single-number measurement that you want to take with big, fat grains of salt. The awesome IRC reports provide both STC ratings as well as critically important performance charts that span a spectrum much larger than that which is accounted for in STC ratings. Learn why STC is a joke in any kind of studio construction context. --Keith :mrgreen:

:oops: My mistake!!!! I had NRC on the brain last night :wink:

Well...After much consternation I'm going with Besser blocks, core filled with cement. I'll paint each side twice and see how it sounds. Pretty echoey I imagine, so I'll be spending time making traps and absorbers and buying a whole lot of Insulco semi rigid, etc to tame the room's beasts. If the soundproofing is not up to scratch, I will build stud gyprock layers on either side. Thanks for the replies :) Lobe

Well...it's a couple of months later and I'm impressed with the results at this stage. The rooms are now built in 110 mm core-filled Besser block. The ceiling is made of two layers of contrasting thickness Gyprock on isolating mounts with Soundstop insulation in the cavity between the upper floorboards. Parallelism has been avoided by building 6 degree angled walls. And there are Raven-brand sealed, non-parallel double doors in the entry and between the studio and booth. The control room is deathly silent. I will not need to build an inner room. I can just hear my wife if she is shouting outside. The isolation between control room and booth is not as good, probably because of the glass windows in the doors, but it is still pretty damned impressive and will be improved when I spend more time sealing the doors with Firesound acoustic caulk. I may add a plasterboard floating room at some stage, but only if I really need to. Most of the instruments I will record will be acoustic strings and vox. The ceiling isolation is great too. The only way you can hear music playing loudly downstairs is if you put your ear to the upstairs walls. As I was warned though, there is a problem with vibration-borne sound, because of the use of masonry and its excellent ability to conduct structural noise, so if my wife stomps about upstairs or puts on the dishwasher or ceiling fans, there are definite, annoying rumbles in the studio. Oh well...I was warned. She'll just have to contain her urge to stomp about and clean when I'm doing a recording session. The other downer is the ceiling height, which is generally 205mm, but is as low as 195 in the middle of the control room. I will be creating ceiling absorbers to tame the ceiling to floor parallelism, but I worry that I will have some major bass problems with such a low roof. Unfortunately, I was unable to build down to legal height because of drainage gradient issues. At this stage I can't hear bass problems In fact, the rooms sound overly bright, but I'll keep you posted. As to be expected from masonry walls, the rooms are very echoey, so my next step is to build bass traps for the corners, absorbers for the walls, throw down a few rugs and see if I can make the room sound dryer and flatter. I've had two glass brick windows installed in the very rear of the control room, to let in lots of natural light and hopefully let out some bass. The glassbricks are great. They are very soundproof, let in lots of light, but stop people seeing in easily. I've had track lighting installed too, the low voltage ones the forum suggested - and I have had formwork trays built into the slab for my wiring. I haven't yet tried out the lights with audio wiring in place. I hope there are no buzzes. My electrician ensured me he had isolated the room's power as much as he could. We shall see...I mean hear the results in the coming week. I will be getting the audio wired up as soon as I finish painting the rooms. When I finish the project I will post some pics. I might even try putting some mp3s to demonstrate the sound isolation. Thanks for this brilliant forum. It has been incredible!

Hey man, I just build out of dense concrete block and have found the same issues.....seems concrete is not great for keeping out sound of people tapping on walls and floors..... Our rooms are crazy for echos...its all rendered perfectly so its worse now the walls are all dead flat, how have you got on?

Yes...The echo is pretty wild isn't it, but I plan to tame it with some lots of Insulco semi-rigid absorbers and bass traps. As for the structure-born noise, it's a problem, but, as long as no one is stomping about upstairs and no one has ceiling fans on, I can get away with it. It's crazy, that I can't hear someone screaming outside my walls, but I can hear an almost silent ceiling fan on the upstairs ceiling. I am still very happy with the studio though. It's coming along very nicely. Lobe :)

Hi Lobe, I am on the sunny Coast :D Could you please tell me exactly what insulco semi rigid batts you used and how much were they ?? much appreciated Cheers N Y M O

Well, I haven't bought them yet, but I plan to get 50mm Insulco semi-rigid batts. I got a price from Insulco on a pack of 5 sheets (2.4 x1.2 m) of $160. I'm planning on getting two packs to build my absorbers and traps. ph: (07) 3805 7733 There's a good plan for a trap at http://www.soundonsound.com/sos/mar06/a ... diosos.htm Absorber plans are in July 2006 Sound on Sound, but I can't find a link to it. Hope this helps and sorry about the delay. Lobe :)

[quote="lobe"]Well...it's a couple of months later and I'm impressed with the results at this stage. The rooms are now built in 110 mm core-filled Besser block. Hi Lobe and others..thanks for telling your story - I am two weeks away from commencing my own under the house recording/rehearsal room project. Iam in Brisbane - I live in a raised Queenslander home which is not enclosed in underneath. IE under the house just has those hardwood slats -no solid walls, and I have recenlty had a concrete floor layed. There will be plenty of bass and drums played in this room and much potential to really annoy my neighbours..which Id like to avoid. I will be building a room about 4.5 x 5.5 with a height of 2.2/2.4m. I am grappling with the decision of either building besser block walls/core filled with sand and also lining the internal walls with a plasterboard/stud partition wall filled with wool insulation(leaving a 20cm gap between the stud wall and bessa block wall). .... OR Using two double layered plasterboard partition/studwalls (with resilent/spacing bars and plenty of mineral insulation wool..the two partion walls would also have a 20 cm air gap between them.)..I would be using 2 layer sof plasterboard on each side of the studs = 8 layers in total. Just seeking advice /wisdom from your learnings/experience....which of my options would be best?..would you do anything differently if you were to go back in time and rebuild your studio?? Also - where did you go for your supplies/materials? This looks like a very informative forum ie ie practical and ideal for the dyi home studio builder- I have read so much from the web - but a lot of it is advertising certain products - so its not that credible. look forward to benefiting from others expereinces cheers Jonno

Good questions. The Besser blocks are a good, secure outer layer and as long as you are building a stud/insulation room within a room inside this, then the besser block outer shell is a good option. Concrete does tend to transmit sound better than wood so keep this in mind too. As for materials, I used insulco semi rigid for the wall absorbers which I got from a place near the Logan Hospital (can't remember the name...something like Discount Insulation.) I used regular pink batts to go inside the plasterboard/stud ceiling. If I was doing the project again, I would put 50mm electrical conduit under the slab before it was poured, and have all my wires in there already. Snaking through wires was a real pain in the #$%%^. I would also have dug deeper to give myself more headroom. Hope this helps. Ross.

Heh - I'd love to see any pics you had of your studio...I'M VERY keen on beser block outside (sand-filled) with Gyprock lined stud wall inner room... Have you built the inner room yet? How is your isolation form the outside world? How does a drum kit sound from outside your studio? Cheers from NSW