Room in a room - floor structure question

[Z-Plane]

Hello all, I'm a regular Tape Op reader, I've lurked for a few years but didn't register as I already spend too much time on music tech forums. I have a question I hope can be best answered here.

I've inherited an old house, which apart from needing plenty of regular work done, has provided enough space for me to construct a soundproof room. First of all, I am a programmer/home producer who likes to crank up the monitors and record loud guitars. So my room only needs to serve me as a comfortable space that doesn't spill into the rest of the house or the neighbour. Its a reasonable ground floor room maybe 15 sq. ft. and I plan to construct an internal room using asymmetrical walls made from 2 layers of thick plasterboard with RW3 or similar between, no windows, practically airtight with a fitted aircon unit, as I can take regular breaks and mostly work alone.

My question - the floor is old floorboards with some kind of resonant space below, so I'm going to raise the floor, but should the new floor be inside or outside the dimensions of the new internal walls ? Also, how much do I gain by fully raising the floor a couple of inches compared to simply lining it with a suitable insulator and new surface ? Thanks for any help.

[roscoenyc]

half on topic.

you mentioned asymetrical walls.
In a room that small they aren't really gonna help you as much as other treatments.
You'll lose space and it wont necessarily help you

You should get the Gervais Book he details walls, floors, soundproofing myths and truths. A big help

[Kelp88]

You've got to raise the floor of your soundproof room up off your floor or else the sound will spread in all directions via the floor cavity. Especially with a wood joist floor (as opposed to concrete, like you might have if you were in the basement) you need a separate floor for an iso room. Normally you want to provide at least a couple of inches of airspace, created by placing rubber isolators, (or a Kinetics "RIM" system or similar http://www.kineticsnoise.com/arch/floors.aspx). Once you have a multiple layer plywood platform (or heavier) on top of the isolators, then you simply build your walls on top of that. Free-standing walls are best, if you can avoid bracing to your existing room. Of course you might want hide the perimeter of the air space under the floor with a vinyl wall base.

Your door will probably be the weakest link if you've got everything else sealed up tight.

You should also get yourself a decent book on DIY studio building. Good luck.

[Waltz Mastering]

As others have said: You will gain great isolation if your new floor is de-coupled from the old floor.

You can use something like this: http://www.amazon.com/Auralex-UBFF-Floa ... B001D4ARKK

Once the floor is in place you will get isolation if you use that new floor to support the new inner walls and ceiling. Saying that, there is more than one way to get the iso you're looking for so do as much research as you can to see what works best in your budget and needs.

Also, don't forget you will need air flow....could get stuffy without it.

[Z-Plane]

Great stuff, thanks so much for the info and links. Speaking of basements and concrete floors, that gave me one more idea. Could it be worth removing the floorboards and joists to work with whatever lies beneath ? Unfortunately I'm not at the house for another week to answer that question, but I suppose a floating floor still has more isolation than a concrete coupling.

you mentioned asymetrical walls.
In a room that small they aren't really gonna help you as much as other treatments.
You'll lose space and it wont necessarily help you

Perhaps, but I was hoping very slight asymmetry would at least prevent standing waves. I've worked from small box rooms before and endured exactly these problems, so as I plan to make this room last a while, I'll probably feel a lot better just knowing its been prevented to some degree. No pun intended - is there an equation for degrees of asymmetry-vs-cancellation in Gervais' book or similar?

Also, don't forget you will need air flow....could get stuffy without it.

Yes, although I think I can trade ventilation for isolation in this case. There will be fitted aircon with no need to go for very long periods shut inside. I do have a design for silent fans and baffles, but for most of the day I will be able to leave the door slightly ajar, its only the potential of loud evening work where I will need maximum isolation. This could be investigated before the build is final.

[roscoenyc]

I think Ethan or JWL could explain it better but the short of it is that splayed walls in a room that small would have to be splayed pretty drastically to do any good. You would loose a lot of real estate doing so. The other way around it is to treat the room with bass traps and absorption.

[norton]

Floating floors.

The most critical component of your "room" is going to be insulation. So you will want to insulate the joists of the floor that's going to be under your "floating" floor.

The most basic and often the most cost effective AND performance effective way to float a floor is to lay down a bed of 2" rigid insulation. 703/814 etc... then lay a subfloor over that. Your subfloor should 3/4"... don't skimp on the 3/8 stuff.


You can then build your walls on top of that platform if you wish. With a room that small I don't think you'll need a structural perimeter or "joists".

It's going to get awful tight building a room that's only 15 square feet though.

If you can swing more space... i think you'll be glad you did. Not only in functionality... but also in ease of construction, and material use etc..

[JWL]

Be careful with floating floors over wood decks. The problem with floating floors is that they are generally only effective down to their resonant frequency. Below the floor's resonance, they pass sound pretty easily, and can sometimes actually resonate, degrading the sound in the room.

Rod explains this in the above-mentioned book.

It's very difficult to get a wood floated floor to have enough mass to get its resonant frequency down to about 10Hz (which is where you want it).

If it was my space, I'd definitely be seeing what's under the floorboards. If you by chance have concrete, then you're probably better off tying your walls directly into the concrete.

See this thread on the Sayers forum for more: http://www.johnlsayers.com/phpBB2/viewtopic.php?t=8173

[JWL]

Just to add to the above: with regard to mass being large enough to get the resonance low enough. Obviously you need to make sure the existing structure can support the weight you need to add. Last thing you want is a collapse.

[Z-Plane]

Thanks, great info again. After going through the links and various other places they took me, I think a new slab is going to be the winning solution. The house is a large terrace about 100 years old with nice thick walls throughout, so I'm expecting the ground to be sturdy underneath the floorboards, neighbours on one side only. I shall certainly track down Rod's book, I'm presuming it covers everything else I need to know i.e. constructing the walls and ceiling, at this point I'm considering RW3 or similar between two sheets of plasterboard throughout, with neoprene and acoustic sealant for any gaps.

[JWL]

Definitely get Rod's book before you start buying materials. Just to make sure it's done right. He covers things in great detail. There are others that are good too, but I just like Rod's.

[Ethan Winer]

I think Ethan or JWL could explain it better but the short of it is that splayed walls in a room that small would have to be splayed pretty drastically to do any good. You would loose a lot of real estate doing so.

You explained it perfectly.

--Ethan