John Sayers' Recording Studio Design Forum Archive

I'm going to ask this one final question before I finalize my decision on whether to float a floor or not. This is what the space looks like:
http://www.johnlsayers.com/phpBB2/viewt ... highlight=

Originally I asked my contractor if it's possible to have sand filling between the 4" x 6" floor joists (with neoprene pads underneath), and he said 4 inches of sand will be too heavy to be safe, since during spring and autumn, the humidity will make it quite heavy.

His suggestion was to use joists that are half the size so there's 50% less sand, and he also suggests mixing the sand with dry concrete to counter the humidity problem. His suggestions sound good in idea, but will it work? Just how much mass does a floating floor need in order to achieve desired sound isolation? Would I even be close to the required mass?

Hello again.

I just finished my studio floor. Built with 45x95mm studs at 600mm centres and filled with sand. Used double layers of 16mm particle board on both sides and added a protective plastic sheet in the bottom for the sand to rest on.

Take my advice on this. Cause I know this for a fact now.

Do NOT hold back on the sand.

I performed several calculations before going to work on my floor and still when it was completed (after a shitload of work, due to many factors) I still had a floor which had its own very distinct resonate freq. So i had to tare it up and fill up with even more sand (and move the vibration gear back to compact it all even more)

The moral of this story is: - "When you think you have enough sand in your floating floor. Chances are, you do not."

As for the idea with the dry concrete, I have no idea. But I do foresee that if humidity is a problem then mixing sand and dry concrete might lead to a change in the uniform nature of the floor filling and thus alter its characteristics. This is just a guess though.

I wish you the best of luck in your floor build. It is quite the patience tester.

/Gash

Be careful using sand, it has the habit to "shift". The vibrations will cause sand to move. mixing it with concrete sounds good. why not concrete all the way?

Like I said in my previous post. When building a sand filled wooden deck it is essential that once it has been filled with sand once, vibration gear is brought in to compact the sand. It's all about filling with sand -> run vibration equipment then rinse and repeat until satisfied.

/Gash

*oops* sorry, gash. I should read posts while awake... didn't have no coffee yet

Luna,

you post in too many sites the same questions - which make it difficult to keep things steady.

this was my initial reply at another site:

Lunatique,

something has gotten very screwed up in the translations here -

you do not build floating floors with joist and sand fill - I don't know where you ever got that idea - but it is completely wrong.

You can build a deck - and damp it with sand - but this is really only usefull with concrete below - it would not work well with wood framed decks.

If you put down pads and then fill with sand - the sand will run below the frames and make the load transfer to it as well as the pads - and in the end it will all end up turning the deck into a sound transmitter - not an isolator.

The weight has to transfer directly to the pucks them self - and it has to be very considerably in order to get the frequency down around 10Hz - which is really what yuo need.

I explained this pretty much in my book - so I am a little confused by the direction you are heading in here.

That aside - this is not going to work at all - neither will his idea.......

Read all about this in Chapter 3 of my book - I devoted quite a bit of time on this very subject - along with some info on wooden "floating" decks.

If you want mass it has to be concrete but it sounds as if that is too heavy for your space.

Rod

Gash wrote: Hello again.

I just finished my studio floor. Built with 45x95mm studs at 600mm centres and filled with sand. Used double layers of 16mm particle board on both sides and added a protective plastic sheet in the bottom for the sand to rest on.

Gash,

you say you had sheathing on the bottom of the deck?

How high was it off the floor below and how did you support it?

One of the problems here (of isolation) even if you are able to raise the deck to get the air you neeed - would be the long term support of the particle board from the weight of the sand........

That plus the fact that the structure runs through (in between the sand pockets) and thus creates a direct flanking transmission path for some frequencies.

Typically - sand filled decks are constructed directly on the deck beneath (usually a thick concrete deck) and are intended to act as means of running conduits beneath the studio so as to allow for them to not com into contact with hig voltage energy sources - as well as creating a means to feed the console.

Please give us more info on what you actually built.

Sincerely,

Rod

For reference information regarding an overview of my build space and dimensions, see this post.

rod gervais wrote:you say you had sheathing on the bottom of the deck?

See, this is where I become uncertain as to what kind of building material is called what in English. I know what the material is called in Swedish and it is quite possible that I have used the wrong word. It is still a guess that the kind of material I used is called particle board. In Swedish it is called "Spånskiva" (if that somehow helps the situation out...)

I used two layers where each layer is 16mm thick. I screwed both layers (first layer odd, second layer even) to the wooden framework. So the order from bottom to top is: 16mm PB -> 16mm PB -> 1mm protective plastic film -> wooden frame -> 16mm PB -> 16mm PB

In between each layer of particle board i added a tixotrop paste (SMP-polymer) which bare a close resemblance to GreenGlue. For those interested in the details of this glue; see this pfd file. Sorry, the retailer only had it in Swedish.

rod gervais wrote:How high was it off the floor below and how did you support it?

I used 50x100x12mm (w, l, h) pads of cell rubber neoprene with a density of 180kg/m^3 and a weight of 2.4kg/m^2. I am not 100% certain but I believe the SHORE degree of the neoprene was/is 70 (ish... i do not have that info where i am at right now)

The floor which I am building this wooden deck upon is a solid concrete floor. The building is industrial and has a mechanical/engineering workshop in the basement. The studio build is on the second floor.

The finished floor now rests apx 11.5mm above the concrete foundation/floor. This is of course an approximation. It should also be noted that this is the resting position of the floor prior to the walls and ceiling being added. According to my own calculations, the final resting position should be somewhere around 10.3 to 10.6 mm when remaining construction has been added. That should result in a 12-18% compression of the supporting neoprene.

It's hard to tell really. Partly because with numbers and math I can get one result... but when building it I quickly realize that there are several factors that might impact the theoretical result in ways that I had not expected.

rod gervais wrote:...would be the long term support of the particle board from the weight of the sand.

I thought a lot about this and ended up calling a local construction company which had supplied a lot of the material for my build. They claimed that with an odd-even particle board construction and with a total thickness of 32mm, I should not have to worry about the load of the sand in a construction like this. If you feel differently, now is not the time to tell me. (But please do anyway)

rod gervais wrote:That plus the fact that the structure runs through (in between the sand pockets) and thus creates a direct flanking transmission path for some frequencies.

Well... I hear what you are saying... and all I can really comment on here is that as far as I know right now, even though the studio room is not completed yet, from what I can tell the deck is just plain numb, dead, solid. But I guess there are more tests that can be carried out on the deck, once the whole room is completed. Where I stand right now though, I have to say I that am content with the result.

rod gervais wrote:Typically - sand filled decks are constructed directly on the deck beneath...

Well, I guess the whole point of me placing my deck construction on a pad matrix is so that I will gain some isolation from noise propagating in the floor construction. And given that there is a mechanical/engineering workshop in the same building, I thought of this to be more or less imperative.

I will attach some pictures to this post. They are low resolution, and things such as lighting etc has not been taken into account. I excuse myself in advance for the poor quality.

Image 1 shows the deck from above with a 30mm air space between the edge of the outer wall structure and the deck. Image 2 shows the deck before the final touches of the sand are started. Image 3 shows the different layers of the deck.

Hmmm... long post. Hope you are still awake.







/Gash

P.s. One thing I did not cover is the positioning of the neoprene support. I guess I can make a separate post for that later, once I publish my complete build.

Gash,

isolated slabs are typically installed 4" or more above existing floors for the purpose of isolation - (102 mm) while your final product here winds up about 1/4" finished (11.5 mm).....

It is not only the mass - but the air spring that creates the isolation - and you have none - with a small air space like that this is almost a one leaf system (the original floor plus your new floor)

I would have to wait until your done to see what you report... but I would pretty much bet you that if you took a sledge hammer and tapped on the top of the deck you would hear it downstairs in the machine room (and thus you will hear them as well.......) And it will get worse as you finish your walls and seal them in.

You're right - that is particle board - and I would NOT have used that to proceed in the manner you did - this because it is a non-structural board only meant to use as underlayment on top of a structural deck.

It is very brittle and I would not have long hopes for it's ability to live for a long period of time.

Sincerely,

Rod

Rod, thank you for your comments so far.

As far as the air space goes; I guess there is nothing to really talk about. You are right and that is the end of it. Sadly I had to cut some corners height wise since I only have 2700mm total building height... and that includes the roof joists that are a part of the main, outer, set of walls.

If I had access to a greater ceiling height I am certain I would have allowed myself a larger air space between the floor and the deck. And looking at things now, after your latest post, I am starting to think that I could have just left out the floating floor all together... (yes, it is said in a million and one places and still people do it)

Regarding your sledge hammer experiment I can say that the facility used to be a printing factory that had large printing presses installed on all three levels. The current machine workshop is in the basement, then there is one floor of regular office space (some consultancy firm) and then there is the floor where I reside. Due to the fact that the building was constructed to withstand the loads of the printing presses the floors on each level where built with additional thickness/reinforcement... at least this is what the building inspector told me when I spoke to him briefly about it. I understand that this really does not "say" anything really useful but I thought I would leave it in here to describe my situation better.

Now then, with this in mind... should I still worry as much as I feel I should... especially with regards to your latest post?

If particle board is not the way to go. What kind of material would you recommend in a situation like this?

Ultimately, if you see no other way out of this. I will tare it down... and rebuild it.


/Gash

A studio I designed in the Phillipeans that recently opened it's doors was similar construction.

Unlimited load capacity - very thick concrete floors - the structural engineers said I could add anything I wanted to.

What I ended up doing was a new design I have never used before - but my analysis suggested that it really should work fine.

What is consisted of was this:

2" of 703 covered with 2 layers of 1/2" plywood with staggered joints - and green glue between layers.

OK - all of that being said - the owner (a great guy by the name of Dennis Cham) decided not to do this in the control room because at the low end of the ceiling we were already down to a 7'6" height - and we had a concrete beam we had to deal with that kept the ceiling low for the first 4' into the room - but we did use it in the tracking room, string room and iso-booth.

When it was all said and done - there was not a single sound that could be heard in the rooms with that floor assembly (which will make it into the next edition of my book) - but the same was not true in the control room.

There was some air handling equipment downstairs hanging from the ceiling that could be heard clearly in that room -

this was solveed (in this case) by Dennis investing some money to decouple that equipment from the deck above - but sound travels both ways - so it is possible that something upstairs could make it downstairs.

If you had asked me for any ideas - I would have pointed you in that direction (the same way I did with Luna in the other forum.

You can see the control room of that studio (and part of the tracking room through the window) here:

http://www.hitproductions.net/blog_index.php

Just scroll down the page......

Oh - BTW - what you see on the contron room floor is not a wood framed deck - (that would make me crazy if it was - right?) It is the frame for the ceiling cloud that is hung off the threaded rods you see coming out of the ceiling above.

Good luck,

Rod

Thank you for the example Rod! I'll keep my posting on recording.org from now on, since that's your "official home." I started posting in multiple forums out of desperation because with each passing day the construction of our new home and my new studio was getting pushed further and further back, and often the really knowledgeable guys are too busy to help everybody at once, so I thought I'd try and see if I can spread my net a bit wider. I think it might've been you that pointed me to this forum in the first place.

not to be an ass, but THIS is the one dedicated forum on studio design....

Ro wrote:not to be an ass, but THIS is the one dedicated forum on studio design....

LOL