concrete slab as floor

Hi All, new here, Ive visited here before whilst researching various studio questions, I hope to spend more time here learning, great site. I have a question regarding a concrete floor in a studio, I had a look at the reference area but couldnt find anything specific to my questions, if I missed it, my apologies. I have a single brick garage which is on a concrete slab (approx 100mm thick), the garage is not attached to any other dwelling, just sitting on its lonesome in my backyard. Its approx 8 meters by 4 meters and approx 2.7 high. I wish to convert the garage into a control room and studio/live room by building 2 rooms (roughly 4 meters by 4 meters) within the garage. As far as soundproofing level goes, I wish to be able to play drums at night without bothering the neighbours. After reading the "do I need to float a floor" info, I will stick with the concrete slab as my floor inside the studio. My questions regarding the existing concrete slab are: 1) Will self leveler change the existing slabs sound isolation properties in a negative way? The reason I need to pour self leveler is because the slab isnt very level (up and down in certain spots and it has a slight overall lean for water to escape during washing), it wouldnt bother me so much in the control room but I'd like to get the studio room as level as possible for drums, etc. If self leveler isnt an option the only other thing I could think of is polishing the concrete. If anyone has any suggestions please dont be shy! 2) Since I intend on building 2 inner rooms which will be sitting on the same slab as their floor, does the slab need a relief cut in the middle to decouple one room from the other creating 2 separate concrete slabs/floors? 3) can you still decide to line the concrete floor with floor boards or similar once the studio is fully built or is this something that needs to be decided during design and construction? I was thinking that I may not like the look of the concrete once the entire studio is done, painted, etc, so was thinking that I might be able to line the floor with timber boards leaving a gap where the boards would meet the walls to be caulked. So far, I have studded up the brick walls, put insulation in, and lined the walls with one layer of 16mm soundcheck plaster. I have also put in a suspended ceiling with insulation and 13mm plaster. Obviously none of this will be seen once the new rooms are done, just thought i'd mention what has been done so far. well, any advice and suggestions are greatly appreciated, thanks,

Welcome to the forum its great to see new builds being put up, :D Not an expert, but read all the posts because I am doing a build myself so have learned a little from these and the answers from the various experts. Il pass a few comments on your post but please don't take anything as 100% because I may not be right. 2 rooms of 4m x 4m may not be ideal as equal dimensions are usually not good for sound but I know nothing more than that as it all gets to complicated for me. :D I may be misunderstanding what you have already done so some pictures would be helpful but it sounds like you may have already created a potential problem as you say you have studded up the brick walls and constructed a suspended ceiling, are the studs fixed to the brick work? What have you suspended the ceiling off? I'm visualising either of the studs you have constructed or the existing roof, so pictures would be good again. Im sure one of the experts will answer your post soon so photos will be wanted by them usually.

Thanks for the reply, yes, the studs are fixed to the brick wall and the plaster fixed to the studs. The suspended ceiling (which is raked following the original roof line) is attached (via drop down anchors) to timber ceiling joists, on top of the ceiling joists is sarking then corrugated sheeting. There is insulation in both the walls and ceiling. The reason I have already made a start (and possibly mistakes) is because originally this was supposed to be a single big "mix/midi suite" room for my own electronic music, no live instruments/vocals were intended to be recorded in there. I mix at very low levels and mostly during the day on Sat or Sun, so at the time I had planned to spend most of the budget on treating the room correctly rather than soundproofing. But since commencing, I have formed a working relationship with some people which requires me from time to time to do some tracking and overdubs, so the purpose of the room has changed midway. Im not going to tear down what ive already done due to the cost already put in so i will have to live with the consequences of the work already done. I understand your point about the room dimensions and the fact that there are optimum dimensions that I should be working too, but I can only work with what ive got so im willing to sacrifice and compromise or at least strike some sort of balance between "building the perfect room" and building something that will be enough for someone at my level (which isnt high), and for someone with a budget! I gotta be realistic and am not expecting miracles. I just want to do the best I can do with the money I have, i'll be more than happy with that! I can take photo's and post, the reason I didnt is because they'd just be photo's of a concrete floor with plaster walls and ceiling, i didnt think they would be informative or relative at this stage to the concrete question I had. I'll take some snaps tomorrow and post. Just a warning its a little messy in there at the moment! :oops: Thanks again,

As I said before I'm not an expert, but it sounds like you have created 2 masses and attached them which is not the best for isolation, With regards to your concrete I would probably say no to cutting it as you may be causing a problem strength wise , although I understand your thinking for separate floors this may be a waste of time as it sounds like your walls are all connected to each other and the floor so you may not be gaining anything. As for wood on the floor I would say it should be fine as long as you do not create a void between the wood and the concrete though there may some better advise from one of the experts

You can level the floors with floor leveler...but you ask the right questions in the wrong order. Had you asked just a few questions before the build started you would have eliminated the square rooms (parallel walls/flutter echo). If I may say this, pictures are not required for this project since you have basically completed it in the manner that anyone here would have tried to steer you away from. These are the types of things we see year after year...so, fix your floor with floor leveler, correct. When you start having acoustical issues and cannot figure out how to tame them due to the square rooms...please start a new thread and be prepared to take a slow journey rather than a fast ride :)

xSpace wrote:

You can level the floors with floor leveler...but you ask the right questions in the wrong order. Had you asked just a few questions before the build started you would have eliminated the square rooms (parallel walls/flutter echo). If I may say this, pictures are not required for this project since you have basically completed it in the manner that anyone here would have tried to steer you away from. These are the types of things we see year after year...so, fix your floor with floor leveler, correct. When you start having acoustical issues and cannot figure out how to tame them due to the square rooms...please start a new thread and be prepared to take a slow journey rather than a fast ride :)

Had you asked just a few questions before the build started you would have eliminated the square rooms (parallel walls/flutter echo). Unfortunately I only discovered this site around a month ago, I started work on the "original idea" for the garage more than 8 months ago, its been sitting still ever since due to cash flow. Im not sure I understand which square rooms you are talking about, I havent built the " rooms within the room" yet. If I may say this, pictures are not required for this project since you have basically completed it in the manner that anyone here would have tried to steer you away from. As mentioned, my garage is nowhere near complete. You can level the floors with floor leveler...but you ask the right questions in the wrong order. Great, I didnt think the leveler would change things that much but wanted to ask people in the know. I dont think I am asking the right questions in the wrong order because basically here's whats happened: 1) decided to turn garage into a SINGLE "spare bedroom" type room to suit at the time required needs and purposes and budget. 2) After commencing, required needs, purpose of garage project changed significantly 3) garage project put on hold to raise more funds and due to requirement /design changes. 3) Discovered this site recently (after original commencement). 4) Now here, reading and asking questions to avoid further possible mistakes. I will still post the photo's anyway. Thanks for the reply,

Here is the garage to date. The roughing in of the electrical was done for the original design and purpose so ignore it. Theres no light fitting in there so I had to take the picture from just inside the door way with the flash on.

Hi "madmuso", and Welcome! :)

Its approx 8 meters by 4 meters and approx 2.7 high. I wish to convert the garage into a control room and studio/live room by building 2 rooms (roughly 4 meters by 4 meters) within the garage.

That might be cutting things a little too small. Once you allow for the isolation walls, you'll have rooms measuring around 3.5m long/wide (although as Brien and Roguejackal both pointed out, you should stay away from square dimensions). That might be fine, but assuming you end up with something like a 3.5m x 4m control room and 3.5 x 2.5 drum booth. Neither is ideal. Have yo considered the possibility of just building a single larger room, and recording in the control room? It might be an option.

As far as soundproofing level goes, I wish to be able to play drums at night without bothering the neighbours.

You should put some objective numbers to that! :) Drums can be loud, and legal noise regulations might be pretty low, so you should look into both of those, get real decibel numbers on them, and figure out exactly how much isolation you need.

After reading the "do I need to float a floor" info, I will stick with the concrete slab as my floor inside the studio.

:thu: :yahoo:

1) Will self leveler change the existing slabs sound isolation properties in a negative way?

It will probably help, in once sense: it will be adding more mass to the floor, which can have a positive effect on isolation: And if your floor is not level, then it's a sensible thing to do, if you plan to lay laminate flooring on it, for example.

2) Since I intend on building 2 inner rooms which will be sitting on the same slab as their floor, does the slab need a relief cut in the middle to decouple one room from the other creating 2 separate concrete slabs/floors?

That depends on the answer to "How much isolation do I need?". But regardless of the answer, the bigger question is "Can you cut the slab?" You'll need to get a structural engineer in to answer that question. That would imply also cutting the foundation, since cutting just the slab is not going to fully decouple. You should have separate foundations and slabs for maximum isolation. Another option might be to cut out a section of slab under just one of the rooms, and pour a new one, with its own foundations, inside the footprint left by the section you cut out. But the only guy who can tell you for sure if / how to do that, is a local structural engineer who knows your local building code.

3) can you still decide to line the concrete floor with floor boards or similar once the studio is fully built or is this something that needs to be decided during design and construction?

Yes you can, but it would have to be some type of laminate flooring. That can be laid directly on concrete, provided the surface is flat and smooth. Solid wood flooring is not so easy to do, and more expensive.

So far, I have studded up the brick walls, put insulation in, and lined the walls with one layer of 16mm soundcheck plaster.

Whoaa!!!!! You seem to be getting ahead of yourself: When you say "studded up the brick walls,", do you mean that you attached the studs directly to the brick, with no gap? If so, that is no use at all for isolation. You'll have to take that off again, and do it correctly.

I have also put in a suspended ceiling with insulation and 13mm plaster.

13mm is too thin. You should be using only 16mm plasterboard (drywall, sheetrock, etc.). 13mm is too flexible, not massive enough, etc.

Obviously none of this will be seen once the new rooms are done, just thought i'd mention what has been done so far.

Why will it not be seen? You are talking about your inner leaf, and it sounds like you have already completed it, so why will it not be seen? You can have only two leaves for your studio: the outer leaf (brick walls and roof, in your case) and the inner leaf (plasterboard on stud frame and suspended ceiling in your case). If you now build something else inside that, then you are adding a THIRD leaf, which means you could be REDUCING your isolation for low frequencies. 3-leaf construction is a bad idea, unless done correctly and only where absolutely necessary. Going on to your next post:

yes, the studs are fixed to the brick wall and the plaster fixed to the studs.

OK; then that needs to come off. It is not doing anything to help you, and is wasting useful space. If you work carefully, you might be able to re-use some of those materials. The stud frame should be built about 2 cm away from the brick wall, and not touching it in any way. It also must not touch the existing roof, ceiling joists, or walls on any other way. Plus, you are talking about two rooms, so you need a separate frame for each of those rooms, and those two frames must also not touch each other. This is the basic method for attaining the type of isolation you are talking about.

The suspended ceiling (which is raked following the original roof line) is attached (via drop down anchors) to timber ceiling joists,

When you say "drop down anchors", are those proper acoustic isolation hangers, or just solid metal/wood hangers? If they are not isolation hangers, then the ceiling needs to come out as well, and be re-built correctly. You probably can never achieve the levels of isolation you are talking about unless you do this correctly.

Im not going to tear down what ive already done

Well, sorry to be blunt, but unless you do there is very little chance you will be able to get the high levels of isolation that you say you need, in order to be able to play drums in there and not infringe on your local noise regulations. Drums are the loudest of all instruments, and can easily hit 115 dB or more. getting that down to the level required by most municipal noise regulations is going to need some pretty hefty isolation, based on a proper 2-leaf MSM system. What you have done already prevents you from building a proper 2-leaf MSM system. That leaves you with the possibility of a 3-leaf MSMSM system, which implies some major extra expenses in terms of mass, and some major extra loss of room space, due to the much thicker walls that you need. So you basically have three choices: 1) bite the bullet, take it out carefully so you ca re-use as much as possible of the materials, and re-build it right. 2) spend a lot of money beefing up what you have done so far with a huge amount of extra mass (three-leaf construction implies that the middle leaf needs twice the mass of the other two leaves), then add your new third-leaf walls, also with a lot of mass, and large air gaps, which will leave you with very small rooms. 3) Be prepared to face the cops every time they come knocking on the door, and spend your money on paying the fines for breaking the law. Those are your only real choices here. There's a thread on the forum that might interest you, of someone else who faced exactly your situation, understood the issues, ripped it all out, and did it right. With good results. I'm trying to post the link, but there seems to be a problem with the web site right now, so I'll add it later, once John has fixed that. You might be able to find it yourself: it's the thread by our member "beeros05". EDIT: FOUND IT! : viewtopic.php?f=2&t=17363&p=120992#p120992

I understand your point about the room dimensions and the fact that there are optimum dimensions that I should be working too, but I can only work with what ive got so im willing to sacrifice and compromise or at least strike some sort of balance between "building the perfect room" and building something that will be enough for someone at my level (which isnt high), and for someone with a budget!

Maybe you missed the point that Roguejackal and Brien were trying to make: A square room is basically unusable as a studio, due to the major modal issues that will be present. A square room with inner dimensions of 3.5m per side just happens to have major modal resonances at 49, 81, 100, 110, 220 Hz, all of which are really close to the fundamental frequencies of parts of your drum kit and bass guitar. You'll never be able to record drums or bass in there successfully. A small change in dimensions would get you away from that terrible situation. There are several good room ratios within reach, if only you would be more flexible and consider changing the dimensions.

I just want to do the best I can do with the money I have, i'll be more than happy with that!

Changing the room ratios will not cost you one cent extra: it just means putting the walls in the right place so that your two rooms are not square, but rather have good ratios.

I can take photo's and post, the reason I didnt is because they'd just be photo's of a concrete floor with plaster walls and ceiling, i didnt think they would be informative or relative at this stage to the concrete question I had. I'll take some snaps tomorrow and post.

Photos are always useful! You can see what you are dealing with, but we can't unless you show us! from text descriptions it is hard to imagine what the situation is really like, but photos help to make it much clearer. .... And now that I'm looking at your photo, there are indeed other issues that need fixing: You have perforated your drywall in many places, for electrical cables. You cannot do that. You are trying to attain high levels of isolation, so you cannot make any holes in your drywall. Any place that air can get through, so can sound. The drywall must be a complete, unbroken hermetic seal around the room, with no holes, cracks, gaps, or weak points at all. The electrical work must be done INSIDE the final room itself, surface mounted. You can have only one single penetration for bringing in the main electrical feed, and that penetration needs to be done correctly to maintain the isolation. The power is then distributed around the room from that point, on the inner wall and ceiling surfaces.

The roughing in of the electrical was done for the original design and purpose so ignore it.

OK, but how are you going to get rid of it, and seal up the holes correctly, with enough mass to retain the isolation level? There also seem to be two strange "kinks" in the side walls that should not be there: they will most likely create edge diffraction artifacts as sound moves past them. Finally, there also does not seem to be any HVAC system in that room. Studios need HVAC! You can't breath for very long inside a studio that is isolated correctly, and things will get awfully hot and stuff within a very short time, especially once you have a musician or two playing energetically in there... HVAC is a must, and you don't seem to have any. Their might be other issues too, but you only posted one photo so it's hard to tell. Fortunately, you have not advanced too far and can still correct all these issues, without losing too much. The overall spaces seems fine for a studio, if done right. - Stuart -

Hey Stuart, thanks so much for the reply, info and advice. First off I just wanna say that, believe me, no one is more frustrated than me that I didnt discover this site years ago. I checked out that link you provided, what a thread! I was sweating just reading it! I have a question from one of the charts on that thread, I was looking at the chart that shows the 2, 3 and 4 leaf wall constructions. Below the triple leaf it says STC53 and below the double leaf it says STC63. Am I right in saying that there is a 10db difference between the two designs? If you were to make the inside 3rd leaf thicker (ie more sheeting) would it improve the differential db? I cant bring myself to yank out the existing plaster, I wont be able to reuse any of it because we went a little crazy with the glue, as well as the cost! So im thinking, I may just have to settle for a studio that is isolated enough to do vocals at night and will restrict myself to doing the odd drum session during the day, im ok with that, I have access to other larger facilities to do full on drum recordings if I have to. Yes, the drop down anchors for the suspended cieling are standard metal ones and now that I think of it I cant remember if the plaster used on the cieling is 13mm or 16mm, I dont even have a piece of offcut to check. All parts/plaster used to construct the suspended cieling were used because I got them (almost) for free from a job site I was working on, they cost me a slab! Do you have any advice on the how to seal the holes where the electrical cables come through? The cables are fixed via clips to the timber ceiling joists above the suspended ceiling, the only thing I can do is cut the cable as short as I can and leave it in the ceiling. There is going to be an electrical sub box in the room so currently all the electrical is hanging there at the sub box location. I gotta take a loss on the cables, so be it. Not much I can do. Given the circumstances I dont think cutting the slab is a good idea, I will just leave it as one and get it level with leveller. I hadnt punched any holes for air con or fresh air becasue I am still not sure where to run it all, both internaly and externaly. Plus I wanna read up on these subjects here first, now that I know this place exists! :D I was hoping that there was a split system aircon/heating unit that can also deliver fresh air. Like I said I will go to the appropriate area here to do my research. thankyou

Hey guys, I read a really good thread yesterday and wanted to revisit it but using the search function I cant seem to find it :( It was a garage turned into a studio and from memory the owner and thread started was Aussie and John helped him fair bit. A few distinct things I remember are, the owner said he was pleased with Johns "inside out" walls suggestion and that they worked a treat. The owner also mentioned towards the end of hte build that some local sound guys were impressed and booked his place for use. I reeeeeeealy wanna read this thread again! Ive been searching for over half an hour. I cant remember how i got to it and idiot me didnt bookmark the page. im not asking for anyone to go searching for it, im appealing to someone who may be familiar with it may be able to point me to it, otherwise im sure i'll stumble across it again, no biggy. thanks,

still searching! I also just remember that the owner mentioned his budget was around $15,000 and they went over slightly. where are youuuuuuuuuuuuuuuuuuuuuuu!! :evil:

Yeah, the search feature isn't too good at finding that kind of thing. I don't recall the specif thread you mention, but there are a LOT like that! Hope you find it.

budget was around $15,000 and they went over slightly.

Naah, that NEVER happens in studio construction! Nobody ever goes a bit over budget.... they always go a LOT over budget! :) :shot: - Stuart -

Still searching like a madman for that thread! I viewed every search result for the word Garage in the title, im 99% sure it had the word garage in the thread title which is why I checked it out. I searched both the studio design and studio construction forums. Do you think it would be ok for me to ask John if he remembers, he seemed fairly involved in that project, he may remember the guys username or real name which may help. i really wanna read check it out again.

I have a question from one of the charts on that thread, ... Below the triple leaf it says STC53 and below the double leaf it says STC63. Am I right in saying that there is a 10db difference between the two designs?

Correct. In other words, from the subjective human point of view, the the double-leaf wall would be twice as quiet. (We hear 10 dB as being roughly twice as loud, or half as loud). So by taking out the third leaf, you make things twice as quite! Surprising, but true... When speaking about isolation a 10 dB change is huge! Having said that, STC does not real measure decibels: it measures fictitious, mangled, tweaked, adjusted "things" that used to have a vague relationship to dB, ... :) STC isn't a good way of measuring sound isolation for studios anyway, but those graphs give you a good idea of the concepts.

If you were to make the inside 3rd leaf thicker (ie more sheeting) would it improve the differential db?

It's not so much the thickness of the leaf, as the mass of the leaf. Mass is what matters. But yes, assuming that you increase the mass of the middle leaf, you would get a small increase in the total isolation. You can also get an increase in isolation by increasing the size of the air gaps between leaves.

Do you have any advice on the how to seal the holes where the electrical cables come through?

Probably acoustic sealant would work, assuming that the holes are not too big. You could also try using mud and tape to patch it, but I'm not sure how well that would work.

I hadnt punched any holes for air con or fresh air becasue I am still not sure where to run it all, both internaly and externaly.

That raises another issue that you might not have considered: ideally, your HVAC ducts should be isolated where they pass through the wall, and the holes must be sealed. You also need to build silencer boxes for the ducts.

I was hoping that there was a split system aircon/heating unit that can also deliver fresh air.

There is one, but I don't recall who makes it. However, it does not supply much fresh air at all: probabaly nowhere near enough for what you need. And you still need an exhaust duct. - Stuart -

Here ya go. http://www.daikin.com/global_ac/product ... ure03.html

Yup! That's the one. Thanks! :) - Stuart -

I have Daikin split units for my rooms, this is the one for the control room and I have the same for the tracking room when built. Very happy with them and with the install when fitted,