2nd floor-floor isolation

Ok, so i have searched and searched and i didnt find any threads about beefing up concrete floor and improving isolation without creating floating floor. Basically my studio is on the second floor of building and i have small hotel underneath me. I am doing post so i will not record drums or bass guitar amps. I want to prevent as much noise as possible getting through to the hotel underneath. My floor is heavy concrete floor with 5 cm cement screed on top. I will use parquette, hardwood flooring as floor finish. What would be good thing to add on top of cement screed to improve isolation? Thank you

I just want to make one thing clear. I am avare that having concrete floor with hardwood glued straight to it is best solution acoustically for acoustics inside the control room. My concern is sound leaving through the floor to the offices underneath and how to possibly improve that concrete floor even further. Thanks again :)

Somebody please have mercy on me :) I am searching for this answer for weeks and there is nothing to be found regarding matter of beefing up normal concrete floor with extra layers of whatever without creating floating floor. Help and stuff :lol:

Hi Daiwa. I've been asking a similar question for a while, and it turns out that the best answer is simply: more concrete! Just lay more concrete directly on top of what you have already, and either finish the concrete neatly to be your new floor, or build your new wood floor directly on top of it, firmly attached. That said, however: Are you sure you actually need to beef it up? Have you tested to see how much transmission loss you are getting at present, with the existing concrete? For example, have you played loud music in your area, measured the level right there in your room, then measured the level in the room immediately underneath yours? You need to have those measurements in order to determine if / how much extra isolation you need. A thick concrete slab should be pretty good isolation already, so maybe you don't actually need anything else in the floor, and you just need to concentrate on the walls and ceiling. How thick is the slab at present? Also, have you checked with a structural engineer to see if the existing structure can actually handle the huge extra load you are going to place on it, with the new walls and ceiling, and maybe also with more concrete on the floor? Several layers of drywall all around and above is very heavy: You need to make sure that you are not going to overload the structure, especially if it turns out that you do need more concrete. But I'd say that your first priority is to get accurate measurements of the existing transmission, in order to decide if you need more isolation, and if so, how much more.

Hi, Stuart.Thank you for helping out. No, i didnt measure noise, but judging from building where i live, which has same concrete floor with cement screed and hardwood on top, that just isnt good enough. To be more precise it sucks. I can hear my neighbours easily even with music being played at moderate levels. OK, i know that concrete floor in this office building where the studio will be, has much thicker concrete but still. I have checked with engineer and extra load on the floor is no prob whatsoever. Your suggestion of more concrete is good one, i guess, but its too late for that now. Its a matter of what to put on top of cement screed, before hardwood finish. Cheers :)

More concrete is the wrong direction, in your case. Being that you are in an upstairs unit, this always makes loading up the floor a potentially dangerous situation. Someone with authority(other then you :) has to sign off on it or the potential for structural failure is great. That said, sand is a material of note used in several builds currently available here at JohnLSayers.com. Mind you these builds are first floor level, so they do not have the immediate issue of weight restriction that you do.

daiwa wrote:

No, i didnt measure noise, but judging from building where i live, which has same concrete floor with cement screed and hardwood on top, that just isnt good enough. To be more precise it sucks. I can hear my neighbours easily even with music being played at moderate levels.

But that's an entirely different building, right? Quite possibly, what you are hearing in your home is not even coming THROUGH the floor at all, but rather is being transmitted through the structure of the building somehow. I'd really, really, really suggest that you do some measurements, to find out what transmission loss you are getting with the existing slab. How thick is that slab, anyway? Since you say that you had a structural engineer inspect it, then he should be able to tell you exactly how thick it is, what its mass is, and how much extra weight you can put on top, safely. Does it even have any mesh or rebar in it? If so, what size and how much? I agree with xSpace: More concrete is most likely NOT needed, unless it is a very thin slab, in which case you can't just pour more on top anyway! But you'll never know for sure until you do the tests.

OK, i know that concrete floor in this office building where the studio will be, has much thicker concrete but still. I have checked with engineer and extra load on the floor is no prob whatsoever.

Are you sure he uhderstands just how much extra weight we are talking about here? Does he realize that there will be several TONS of load going on top? Did he tell you exactly how much weight you can put on top, safely? It is NOT fine for hm to say "Sure, you can put more weight on top". He needs to tell you exactly how much more, and he needs to do it in writing, and signed. And I'm not just talking about "more concrete" here: I'm talking about everything else too. Have you figured out the weight of all of the construction materials that you are going to need, plus the equipment and furniture you are going to install, plus the people and instruments that you might have in there? It might shock you just how much mass we are talking about here. I think you need to do the math, talk to your structural engineer again, and get him to sign off on exactly what it is that you plan to do.

daiwa wrote:

Its a matter of what to put on top of cement screed, before hardwood finish. Cheers :)

Hardwood finish isn't going to be much different from a concrete finish. Both are reflective acoustically. Read Mike Vales thread: http://www.johnlsayers.com/phpBB2/viewt ... sc&start=0 Maybe you can get some ideas from there.

Ok, so i have found out that concrete slab is 25 cm thick, plus there is 12cm of glaze on top of it. Extra load is not an issue. I might as well build brick walls and brick ceiling as far as they are concerned. This is a serious construction, not an "Hey, i think that wind just blew the roof off" type of building. Anyway,my intention is not to affect acoustics of the space but to improve isolation, i just want to beef up that concrete floor with something simple if something simple can be done. So i will not pour new concrete, or float the floor. What do you think of rubber sheets underneath osb boards for mass, they are pretty heavy? Or what do you think about 80 kg/m3 Rockwool under osb boards? Or both? Thanks for helping :)

Ok, so i have found out that concrete slab is 25 cm thick, plus there is 12cm of glaze on top of it.

Wow! That's roughly 10 inches of concrete, plus another 5 of glaze? That's pretty thick. What was this place used for before, anyway? Just curious as to why it would need a 15 inches of floor thickness. You could probably drive a tank across 10 inches of concrete! Anyway, from my understanding, it doesn't look like you need anything else at all on top of that. Adding layers of rubber or plywood just isn't going to make a lot of difference, considering the amount of mass that you already have in your floor. You already have a LOT of "beef" there, and adding more is not going to buy you much extra isolation at all. Just stick your final finish floor (whatever it is) right on top of the existing floor.

Soundman2020 wrote:

Wow! That's roughly 10 inches of concrete, plus another 5 of glaze? That's pretty thick. What was this place used for before, anyway? Just curious as to why it would need a 15 inches of floor thickness. You could probably drive a tank across 10 inches of concrete! Just stick your final finish floor (whatever it is) right on top of the existing floor.

Hey Soundman. 10 inches is pretty standard stuff overhere. I must say that i am puzzled by constant insisting by members here that i check first with my structural engineer about extra load. I have never in my life heard of somebody checking for extra load to the floor when building and i am not young i can assure you. I guess buildings overhere are from the start built to avoid any issues like that.I remember the look on the face of structural engineer when i asked him about weight on the floor maybe being an issue. He was like:"Ha,ha,ha-extra load being an issue?!?!! Please go to you room,put some more reverb on the backing vocals and dont bother me with stupid questions about construction anymore." :lol: Anyway,place was not used before, because there was no place before. 8) It is a completely new 6 storey building which is being built as we speak. Thanks for the advice. I will do as you say. Just tell me one thing. Would you first put one osb board on cement screed and then glue hardwood finish to the osb board or would you just glue the hardwood directly to the cement screed? Also is there any point of using some kind of roofing felt underneath? Thank you for helping :)

Would you first put one osb board on cement screed and then glue hardwood finish to the osb board or would you just glue the hardwood directly to the cement screed? Also is there any point of using some kind of roofing felt underneath?

Two excellent questions! I wish I could answer them, since I'm in more or less the same position as you are: deciding how to finish my floor. I'm hoping that Andre or Ro or one of the other experts can chime in here with suggestions for you!

You can add the finishing floor directly on the cement floor. If the floor is perfect level that is. But, to keep it from "cracking" and "rattling" to much and adjust for nasty gurus in the cement floor, I would add a felt (semi rigid) or alike between the cement and wood floor. (or glue it on the cement floor, I've done the same with my woodfloor at home, it's perfectly still when walking on it!)

Thank you Ro. Will do that. Thanks Soundman. Cheers everybody

Ok, so it comes another question for you experts. What do you think about me putting 1 inch of sand on top of 25 cm concrete and underneath my cement creed glazing? Would that make any difference? No,the weight is not an issue. :roll: Again, i am trying to improve isolation to rooms underneath me, and as you can see i am pretty concerned. I have some kind of gangsta family hotel underneath, for Christ sake!! I dont want to end up as a "fiber" in a fiber reinforced concrete floor :P Help and stuff

Ro gave you the best answer. Any separated surface will create a second leaf and low frequency isolation will be reduced. 30 cm of concrete will give you greater than ~35 dB isolation from 63 Hz up. Very impressive. You have not mentioned what the ceiling on the bottom of the floor is. If you are seriously concerned, do some sound isolation tests. Good luck. Andre

Has any-one ever tried green Glue on a floor yet?

AVare wrote:

Ro gave you the best answer. Any separated surface will create a second leaf and low frequency isolation will be reduced. 30 cm of concrete will give you greater than ~35 dB isolation from 63 Hz up. Very impressive. You have not mentioned what the ceiling on the bottom of the floor is. If you are seriously concerned, do some sound isolation tests. Good luck. Andre

How can 1 inch of sand create second leaf? There will be no air between concrete and cement screed,only sand. Thank you

With a 10 inch+/- concrete floor, I do not know why you are even concerned with adding to it. You are in a good place. Most only get 5/6 inches and even that is pretty good ;) But to each his own I suppose. If you haven't completed some testing on this floor concern, I would recommend it, highly. You may find that it isn't as bad as you are thinking it is. As always, good luck, Brien

With a 10 inch+/- concrete floor, I do not know why you are even concerned with adding to it

Exactly. The math doesn't make any sense: Concrete weights about 2400 kg/m^3. Dry sand weighs about 1600 kg/m^3, or only about 67% as dense as concrete. So adding one inch of sand to 10 inches of concrete will increase the mass by less than 7%. To get a 6dB increase in isolation, you need to DOUBLE the mass. Increasing mass by 7% is not going to make any difference at all. Just a tiny fraction of one dB. I can't even be bothered to do the math on that, but you would not even be able to measure the difference. It makes no sense to lay an inch of sand on ten inches of concrete. To make a worthwhile difference, you'd need to lay FIFTEEN INCHES of sand. That would be over 600 kilograms of weight per square meter of floor space. I don't recall the dimensions of your floor spaces, but assuming just 10 x 10 m, if you DID put 15 inches of sand on it, you'd be adding around sixty thousand kilograms of weight to your floor. And all you would gain by that is maybe 6dB of isolation, theoretically. Like xSpace said: If you are concerned about sound transmission to the space below you, then do some real measurements.

Thank you all for helping out and expressing your views. I get the point. I know i should be safe, i am just being paranoid. I see that consensus is not to touch anything. I will do that. Thank you very much for your help again. Cheers :)

(without re-reading all above text) Is your only concern isolation and wanna improve your already concrete floor with more mass? Why not poor more cement/concrete directly on top of it? Sand will shift, forget it.

Ok, new day-new issue. :roll: So we have built HVAC and walls, and now the time has come for some ceiling. Where to start,where to start? Plan is to suspend metal construction from the concrete floor above,and fix two Knauf gypsboards to the metal construction, basically following same design like in the walls. Only problem is with Rockwool and recessed lighting. Ideally Rockwool should be placed directly on top of metal construction. But that will create many problems for which i would need two pages to explain. My English is quite limited. Anyway my question is, do you think that fixing Rockwool straight to the concrete floor above and not on the top of metal construction below would change anything related to isolation for the worse? Because if i can do that, it would save my life and would keep my medical bills in control :)

I just have to post this photo. Its off topic but just for people to see how HVAC can look when you want to fit everything in one small space. I would say it looks like what octopus would look like if it was featured in Alien 3 :shock: :)

As a place that adapts to suit the people who use it, rather than making people adapt to suit it. Functional and friendly, inviting and individual. (-Spam link removed by moderator-)