Final advice before I take the $50,000 plunge?!

Hey all, I'd just like some of your informed opinions on my project to make sure there's nothing I've missed! Im in the final stages of starting a rehearsal/recording studios business. My main concern is that my rooms will be soundproof enough to prevent any major leakage between the rooms. I will be building 3 rehearsal rooms, 1 recording/rehearsal room and one control room. The premises will be a "shell" warehouse structure, within which I will create the rooms from scratch. I am trying to decide between a solid concrete wall or wooden framing for my "exterior" room wall, illustrated below. Each room will be made up of exterior and interior decoupled walls, with a 4" air gap between them. The wooden framing walls will be made from 2x4's, stuffed with 100mm of Rockwool Insulation, two layers of plasterboard with Green Glue between them on the outer side and chicken wire on the inside to hold the insulation in place. The cost of each is similiar so are there any major differences in sound reduction between the two?

Define "4 inch air gap." Are you counting the thickness of the framing? Or are you saying the framing will be four inches away from the outer wall? If the framing will be 4 inches away, then your air gap is actually bigger than 4" (which is a very good thing). Don't use chicken wire to hold the insulation in place. It may rattle. Instead, use nylon straps. Let's see your floor plan and photos! --Keith :mrgreen:

I can calculate the actual TL's of each scenario, if you'll include complete dimensions and materials - easiest way would probably be for you to add dimension lines to your sketch - if you've not done this before, let me know and I'll post an example... Steve

sharward wrote:

Define "4 inch air gap." Are you counting the thickness of the framing?

No, including the framing the gap would be roughly 12", which as I've seen you post previoulsy is the best size for the return performance. :) Knightfly - I havent settled on a chosen premises yet, so room dimensions havent been finalised, as they may need to be altered depending on the space I end up taking! Roughly, the rooms will be constructed 'room within a room' style. Proposed measurements would be 20ft X 15ft X 8ft high for the inner room, and the outer room would then be 22ft X 17ft X 9ft high, so as to fully surround/encapsulate the inner room. The floor will be a concrete floor, with a 1/2 inch Neoprene sheet layer on top, then hardboard, then laminate flooring. The constructed floor will have a 4" gap around the edges, which will be filled with accoustic sealant so that the floor does not come into contact with the walls.

You're going to put 4 rehearsal rooms and a control room in a 20ft X 15ft X 8ft space??!! Is your customer base going to be Hobbits and Leprachans (sp?) What kind of instruments are going to be in the rooms (assuming the above is NOT correct). Drums will require a different construction/isolation approach than say a piccalo or harmonica (which may be the only instruments you COULD fit in the rooms if the above IS correct. I second sharward and knightfly's requests for more information and dimensions. If I interpret your drawing correctly, I think you've got a serious third leaf problem. If your $50,000 number is close to accurate, you might SERIOUSLY consider paying for some professional advice (on design and construction I mean). It could save you a fortune in the long run it's a lot cheaper to do it right it from the start than to find you've created something less than perfect and have to start over. len

No, those dimensions are PER ROOM! :) Instruments wise, the rooms will be equipped with standard rock band setup; 2 Guitar Amps, Bass Amp, Small PA, and Drum Kit (on a riser), so the music will generally involve some or all of those instruments. As for the drawing, that was just in reference to my question about concrete or wood walls. The left image is two wood framing walls, inner and outer. The right image is as above but with one concrete wall and one wood framing wall. I was wondering if there would be much of a difference in performance between them. I dont have a third leaf problem, and I'm aware of not having a 3 leaf wall structure. Really what im looking for is some assurance that my basic design premise is sound and that two 4" thick walls with double layers of plasterboard and a 4" airspace will provide enough soundproofing for my needs.

If your description was for each room, does the same apply to the floors? Will each room have a separate isolated floor from the others? Why would you build the floor INSIDE the walls instead of building the walls/ceiling ON the isolated floor (a la sharwar's studio)? Also, are you planning on building 4+1 rooms within rooms? I.e., is each rehearsal room going to have an inner and outer set of walls? If so, I think your actually ARE building third leaf systems. 5 of them. I would think you would get much better isolation if you spent the money you were going to spend on the outside rooms to beef up the inside rooms. Just my thoughts. len

Thanks for your thoughts Len, I appreciate it! Firstly, each room will have it's own seperate isolated floor. As far as I'm aware floating the floor by my system inside the room is basically as effective as building the entire room ON a floating floor, but cheaper and easier. The room floor is isolated from the building floor with the Neoprene and Hardwood, and the gap around the edges is filled with an acoustic sealant which will pass on very little vibration from the floor to the walls. Each room WILL have an inner and outer wall, but by my understanding it will not be a three leaf system. It will be basically like having two sealed boxes, with the smaller one fitting inside the bigger one with an airgap between them. :) The make up of the walls from outer to inner will be; Outer Wall: Dual Plasterboard Sheets - (ON) - 2x4 framing with 100mm Rockwool - wire strips to hold insulation in place 4" Airgap (actual AIR) Inner Wall: wire strips to hold insulation in place - 2x4 framing with 100mm Rockwool - Dual Plasterboard Sheets. So between the two walls there is no Plasterboard, just the Air Gap and wire to hold the insulation. Thats LEAF - AIR - LEAF isn't it? The ceiling will be basically like a wall in its side. The Inner room walls and ceiling will be completely sealed airtight, and the doors will be solid core with Compression latches fitted. I think this is the best and most cost effective way of doing this, but I really want to hear everyone else's suggestions and thoughts! Thanks, Barry.

crowbar0 wrote:

So between the two walls there is no Plasterboard, just the Air Gap and wire to hold the insulation. Thats LEAF - AIR - LEAF isn't it?

If you only consider each room by itself, yes you'd be ok. But I was thinking that these 4+1 rooms will all be next to each other so my concern was have a triple (quadruple actually) BETWEEN ROOMS. If I've misunderstood the positions of the rooms relative to each other, I appologize. If the rooms are going to be right next to each other, I would still think that you would get much better bang for your buck (and isolation) if you built only the inner rooms (on separate floors of course) with separate ceilings, and then if for example, you had a hallway with all of the rooms along one wall, you'd build a second wall along that hallway with an air gap. You could take some of the drywall you had planned to use for the outer rooms and put that drywall inside the individual rooms (maybe three layers in each room. The balance of the drywall would go to beef up the hallway wall. I hope that is a little clearer. In the absence of a floor plan, I'm only guessing here. len

len-morgan wrote:

If the rooms are going to be right next to each other, I would still think that you would get much better bang for your buck (and isolation) if you built only the inner rooms (on separate floors of course) with separate ceilings, and then if for example, you had a hallway with all of the rooms along one wall, you'd build a second wall along that hallway with an air gap. You could take some of the drywall you had planned to use for the outer rooms and put that drywall inside the individual rooms (maybe three layers in each room. The balance of the drywall would go to beef up the hallway wall.len

That was my original plan Len, but then I started thinking I'd get more isolation out of this method! I have to go out for a few hours but I'l stick up a basic floorplan when I get back, just to clear things up a bit! Cheers, Barry

Here is a VERY Basic Floorplan (Done with Paint). Dimensions are a bit of a sticking point at the moment, because I havent found a suitable enough building yet, so dimensions would be adjusted to fit the building shell. You can take the room dimensions posted earlier as a ballpark though, as all rooms (except Control Room) will be at least 300sq ft each.

Do you care what the sound level is in between rehearsal rooms, or just while inside any given room (or outside the entire facility)? Laminated flooring over sheet neoprene won't do much of anything for isolation, so it's likely that the floors (and probably ceiling, depending on construction) and doors will be the weak links. If you want enough isolation so individual bands don't try to play to their neighbor's beat, I'd consider floating concrete floors and building SINGLE, HEAVY walls (probably inside out) on TOP of the floated concrete. More expensive, but if no one wants to rehearse there because of bleed, what's THAT cost? Steve

Don't miss this thread. 8)

knightfly wrote:

If you want enough isolation so individual bands don't try to play to their neighbor's beat, I'd consider floating concrete floors and building SINGLE, HEAVY walls (probably inside out) on TOP of the floated concrete. More expensive, but if no one wants to rehearse there because of bleed, what's THAT cost? Steve

I do want enough isolation so bands cant hear the other bands enough to put them off, but I just dont have the budget to float 4 seperate concrete floors! I've seen that exact neoprene/hardwood/flooring method used in a rehearsal studio in England and it claims that it's very effective. All drums and amps would be on risers as well, to seperate them from the floor. What exactly do you mean by "inside out" walls? I've searched it but I cant find an exact explanation.

It's a framing technique developed by John to save a bit on lumber; you build the wall frames on the floor, add all the mass to the upside, then tip the frame into place; this puts the frame on the INSIDE, where you can put insulation between the studs and cover with cloth. Saves needing more framing to contain the insulation batts. Risers will help by several dB, here's one method - http://www.johnlsayers.com/phpBB2/viewtopic.php?t=4013 HTH... STeve

Regarding the floating floors, I was looking at this method on SAE and I think I could do it within my budget. If I was to frame out my floor space area per room (300sq.ft), then construct the floor as specified within the framing, when the concrete has dried and the framing is removed would the resulting raised structure be strong enough to support my large wooden framing walls?

First thing would be to know the strength of your place, and since you don't have one yet it's kind of a moot point. Second thing is, I've never floated concrete on rockwool so don't know how dense you'd need to support the weight - 4" concrete weighs approx. 50 lbs per square foot. If you've read through the REFERENCE section you know how to calculate/measure deflection for any type of rubber under wood floor joists and concrete, which can have better isolation than what you propose simply because of the increased air gap (damped with rockwool of course) - here's a sketch I did for Hugo some time back - speaking of which you need to crop the excess blank space out of your room construction sketch and re-post it; I tried but ran into a really wierd error and lost it... Steve

Steve, no sketch... :roll:

Yeah, got the Slackmaster on it... :?

If you mean the strength of the floor in 'my place' then it will be a solid concrete floor so I dont think I should have any problems with it supporting the weight of the floors. I've been looking at "Aaronw"'s floating floor thread, and I'm now leaning towards doing something similiar, almost identical in fact. I think it should provide the isolation I need, and is a lot easier and more cost effective than floating concrete! :)

Aaron is in a HOUSE, and doesn't have (IIRC) ATTACHED neighbors; and if you price sheet building materials, you might be surprised at which is cheaper. A 4x8 section of floor with 2 layers of 3/4 OSB and a layer of 5/8 gypsum would cost around $45 (framing extra), while the same area of floor using ONE layer of 3/4 OSB and 3" of concrete would run about $20 for the OSB and about $25 for concrete - the OSB/gypsum floor, set on 2x4's and pucks, would have a m-a-m resonance of about 34 hZ - while the concrete/OSB floor, set on the same framing, would have a m-a-m resonance of about 17 hZ. Bottom line - same price, one OCTAVE lower m-a-m, meaning one octave lower for the same transmission loss... (Of course, if you ever intend to REMOVE the floors the concrete would make it a bit tougher :? ) Steve

knightfly wrote:

(Of course, if you ever intend to REMOVE the floors the concrete would make it a bit tougher :? ) Steve

Good point! All depends on the terms of my lease really. Just with regard to using neoprene pucks, what is the prefferred method of securing them to the floor, and then securing the framing to the pucks? Contact cement? Because if one of the pucks were to move or the framing was to slip it would probably bring down the whole room!

That was one of the challenges that led me to abandon the concept of floating a slab. Here in California, building codes are such that floating is difficult to reconcile with code -- perhaps not impossible, but difficult, in that it's probably something that would require a waiver from the building department chief once they're convinced the strength and longevity is equivalent or superior to conventional code-defined methods. That's a heavy burden to prove, and one that probably requires a lot of expensive structural engineering drawings to support. :roll: