existing building - new ceiling conundrum.

[intheshire]

Hi there,
My name is James, I'm in Lincolnshire - England and I'm working with friends to design and build a recording studio/practice and control room.
The space we've got to work with is an old Victorian red brick industrial building. It is in a light industrial area and there are residential houses less than 50m away. The ground floor is a single concrete slab and the first floor is a heavy timber floor over joists - both open plan (5.6m x 11.5m). The ceiling height is 2.85m on the ground floor with another 30cm between the bottom of the joists and the floorboards. We plan to put a live room and storage area on the ground floor and control room on the first (directly over the live room). The thing that is puzzling me at the moment is how to stop as much transfer of sound between the two floors as we can without losing too much ceiling height downstairs. We've got quite a small budget and we're trying to be as economical as we can with materials. Most of the build will be done by ourselves.
Because the walls of the ground floor are made up of lots of different materials (windows blocked up and a large roller door boarded up and foamed) I was planning on building a sand filled block wall within the existing walls, tying it in to the existing concrete slab. This would secure the spaces, give us a heavy insulated shell and fresh surfaces to work from. The concrete slab floor I think is thick enough not to need a floating floor. Then within the block shell build a floating stud frame with layers of plasterboard, void and insulation. I've seen there are plenty of solutions already out there in the forum covering this.
The puzzle I can't work out is the ceiling. Not losing too much height whilst minimizing transfer between the ground and first floor...
There is 28cm of space from the bottom of the joist to the floorboards and I wondered if it would be possible to insulate the voids between the trusses and hang a ceiling from the existing floor joists using acoustic hangers? With this option I can see problems of detailing the corners of the ceiling to the block walls. The other option I thought might work (I know there are probably lots more) would be to put joist hangers on the new block wall (possibly intermittently between the existing joists - taking up some of the 28cm) and suspend a ceiling from these? I think this would be simpler to detail but would lose us some height downstairs and would possibly be more expensive.
Thanks in advance for any help and if you need any more information just shout and I'll do as much as I can to answer any questions.
In the meantime I'll be scouring the other pages of this forum to try and work out the other 1001 (studio related) conundrums I've got!!!
james

[Soundman2020]

Hi James. Welcome. But please read the forum rules for posting (click here). You seem to be missing a couple of things!

I think the first question here that you need to answer is "How much isolation do you need?", but in objective terms, as in "I need at least XX decibels of isolation". Everything else is just guesswork until you can answer that. Nobody can say whether you need 12 inches of concrete, an inch of steel-plating, sand-filled bricks, or just a sheet of plywood to isolate your room. All of the above are possibilities, but the one that YOU actually need for YOUR room, depends on one thing alone: how many decibels of isolation you need.

That's easy enough to find out: with a simple sound level meter (they cost less than US$ 100 on e-bay or Amazon.com) measure two things "How loud you are" and "How quite you need to be". The difference is how much isolation you need. So set up your worst-case session in the location where you plan to build the studio, get your worst-case loudest-ever musicians, put them on your worst-case loudest instruments (all turned up to at least eleven), and tell them to go as crazy as they possibly can. Measure that on your meter, in several locations in and around the site, noting down the level at each point. Then tell them to shut up, send them all home, and wait for the quietest time of day when you expect you'd need to use the place (eg, 3 AM). Now measure the level of "quiet" at each of those locations once again. The difference is how much isolation you need.

Based on that number, you can then look at any of several research publications to find a construction technique that provides that amount of isolation, and fits your budget, and that you feel able to build. There are literally hundreds of possible ways to build a wall, floor or ceiling, and all of them provide different levels of isolation. All of them have been tested in acoustic laboratories, and the results have been published, so it is really as simple as paging through those to find the ones that provide the number you need, then see which one you like most.

The ground floor is a single concrete slab

Excellent! Nothing better, assuming that it is poured directly on the ground (ie, no basement, crawl space, or other air gap underneath). If that's the case, then unless you need really extreme isolation, you are fine. So your floor is already finished! Nothing more to do there...

and the first floor is a heavy timber floor over joists

Not so great! Basically, that's a giant drum head, and will vibrate at certain frequencies, which are the natural resonant frequencies of the structure itself. Just like any drum head, it will vibrate in sympathy with the notes that it is tuned to. That isn't so easy to deal with, but it still can be done.

The ceiling height is 2.85m on the ground floor with another 30cm between the bottom of the joists and the floorboards.

That's a reasonable amount of height, and the gap can be put to good use.

We plan to put a live room and storage area on the ground floor and control room on the first (directly over the live room)

Not such a good idea. Rooms on upper floors are notoriously hard to isolate successfully, for the reason outlined above (giant drum head) plus others. Perhaps moving the storage upstairs would give you enough room to put the control room downstairs?

The thing that is puzzling me at the moment is how to stop as much transfer of sound between the two floors as we can without losing too much ceiling height downstairs.

Mass. that's both the solution, and also a problem in itself. Isolation requires mass (among other things), and your existing structure may or may not be able to handle the amount of mass you need. Only a structural engineer can tell you for sure, but in order for him to do that, he needs to know how much mass you need, which once again goes back to the issue of "How much isolation do you need". There's a relationship between the amount of isolation and the amount of mass.

We've got quite a small budget and we're trying to be as economical as we can with materials. Most of the build will be done by ourselves.

Then you really, really, really should consider NOT building the control room upstairs. It's very unlikely that you'd be able to do that successfully on a limited budget. Despite what you might read on some web sites, there are no magical materials not magical techniques for building studios. All materials and all techniques still have to obey the laws of physics, so don't get sucked into the trap of thinking that there are products of methods that can bypass the laws of physics. Unfortunately, nothing can, even though some web sites try desperately to convince you otherwise.

I was planning on building a sand filled block wall within the existing walls, tying it in to the existing concrete slab. This would secure the spaces, give us a heavy insulated shell and fresh surfaces to work from.

It's a start, but the overall isolation of the room is only ever as good as the weakest part. In your case, that happens to be the ceiling. So if (for example) your sand-filled block walls were to get you 60 dB of isolation but your ceiling only gets you 40 db of isolation, then your TOTAL isolation is only 40 dB. Not 60.

The concrete slab floor I think is thick enough not to need a floating floor.

Very likely, but once again you'll only know for sure by figuring out how much isolation you need. And floating floors are really, really hard to do right, and really, really expensive to do right, so hopefully you will not need to do that. Actually that's one of the great myths of home studios: in reality, very few studios need floating floors, but many of them get poorly built floating floors anyway, then the owners wonder why their room is firstly not isolated the way they wanted, and secondly sounds so terrible...

Then within the block shell build a floating stud frame with layers of plasterboard, void and insulation.

Floating your walls is just as hard to do as floating your floor, and is just as unnecessary. Very seldom does a home studio actually need to have the walls floated. Once again, the calculations for doing that right are complex, there's about a million ways to get it wrong, just a tiny handful of ways of getting it right, and the possibility of hitting one of the "right" ways purely by chance is roughly zero. You'll probably find that all you need is to just build a decoupled stud frame for your walls, where "decoupled" simply means that it only touches the floor, nothing else. So it is not attached to the "outer" walls around it, or to the joists above it: it stands alone, all by itself, firmly bolted only to the floor. That's what you need for the vast majority if cases. No floating necessary. Then you just put a layer or two of drywall on only ONE side of that framing. Done.

The puzzle I can't work out is the ceiling. Not losing too much height whilst minimizing transfer between the ground and first floor...

Provided that you don't put your control room up there, and don't need huge amounts of isolation, the simplest solution is probably RC-1 (resilient channel, type 1) with a couple of layers of 5/8" drywall hung from it, possibly with Green Glue in between. But I'm just guessing there; once again, the only way to know for sure is to determine how much isolation you need, and check the papers for construction methods that get you there.

I wondered if it would be possible to insulate the voids between the trusses and hang a ceiling from the existing floor joists using acoustic hangers?

That's another option, but more expensive, more complex, and wastes more space.

With this option I can see problems of detailing the corners of the ceiling to the block walls.

No matter which way you hang your inner-leaf ceiling, it can never, ever get anywhere near the block walls: It can only ever touch the new inner-leaf walls, which will be the new stud framing that you put up. Your inner-leaf and outer-leaf can NEVER be permitted to touch, anywhere. No mechanical links at all.

The other option I thought might work (I know there are probably lots more) would be to put joist hangers on the new block wall (possibly intermittently between the existing joists - taking up some of the 28cm) and suspend a ceiling from these?

That MIGHT be needed, if your existing ceiling joists cannot handle the load of the new ceiling, but once again you are going to lose a lot of height like that. Hopefully RC-1 will be a solution that provides you with enough isolation. Or maybe RSIC clips plus hat channel.

In the meantime I'll be scouring the other pages of this forum to try and work out the other 1001 (studio related) conundrums I've got!!!

You only have 1001 conundrums to go? Wow! How come so few?


- Stuart -

[G-Sun]

There are literally hundreds of possible ways to build a wall, floor or ceiling, and all of them provide different levels of isolation. All of them have been tested in acoustic laboratories, and the results have been published, so it is really as simple as paging through those to find the ones that provide the number you need, then see which one you like most.

Where do I find this information?

[Soundman2020]

Where do I find this information?

Many places. Perhaps the best is the National Research Council of Canada. Check out their web site, in the section on acoustics. It is a treasure trove of excellent, detailed research. In particular, look for IR-761 and IR-766 to get you started...

Another excellent paper is the Wyle report, from Wyle Laboratories, dated 1973. WR73-5R. Not sure where to download that, but I'm sure it will turn up somewhere if you Google it.

The BBC is another great source. They have a huge library of research papers going back decades.


- Stuart -

[G-Sun]

Where do I find this information?

Many places. Perhaps the best is the National Research Council of Canada. Check out their web site, in the section on acoustics. It is a treasure trove of excellent, detailed research. In particular, look for IR-761 and IR-766 to get you started...

Another excellent paper is the Wyle report, from Wyle Laboratories, dated 1973. WR73-5R. Not sure where to download that, but I'm sure it will turn up somewhere if you Google it.

The BBC is another great source. They have a huge library of research papers going back decades.

Thanks!

[Carl Hungus]

So it is not attached to the "outer" walls around it, or to the joists above it: it stands alone, all by itself, firmly bolted only to the floor. That's what you need for the vast majority if cases. No floating necessary. Then you just put a layer or two of drywall on only ONE side of that framing. Done.

Interesting info Soundman, thanks. I have a question about your above statement, if you don't mind. I was hoping to do exactly this with my new walls, or at most have the top plate for the studs be attached to a resilient channel, which in turn would be attached to the outer leaf joists above. But my builder said that walls that aren't attached up top to at least a new set of inner joists (thereby lowering the ceiling) would be unsound and may buckle. Obviously you've successfully made walls that are only anchored on the bottom, so is there any particular way you anchored them? Did you use metal or wood studs?
I would love this to work for me as it would be advantageous for my ceiling height to just float a new ceiling on channels off the existing joists and not have to run new joists across the inner walls.
thanks

[Soundman2020]

I was hoping ... to have the top plate for the studs be attached to a resilient channel, which in turn would be attached to the outer leaf joists above.

That isn't the purpose of RC, and unfortunately you can't use it that way. RC is meant to be attached to studs or joist on one side, and have drywall attached on the other side.

But my builder said that walls that aren't attached up top to at least a new set of inner joists (thereby lowering the ceiling) would be unsound and may buckle.

Not necessarily. It needs to be braced in some form, yes, but it does not need to be (and cannot be) solidly nailed to the joists above, or the walls around it. If you are not planning to attach your new inner-leaf ceiling to the same inner-leaf studs, then you can use proper isolated sway braces to support the tops of the wall, and use plywood in addition to / instead of the drywall as the first layer of mass, which will give you great strength in sheer.

Did you use metal or wood studs?

Either is fine, as long as they are correctly dimensioned for the job (correct gauge steel, for example).

I would love this to work for me as it would be advantageous for my ceiling height to just float a new ceiling on channels off the existing joists and not have to run new joists across the inner walls.

If done correctly, there would be no difference in the actual acoustic height of the ceiling. You might have joists below (if you build inside out) or not (if you build "interleaved"), but the final ceiling height should be the same, unless you have unusual conditions up there...


- Stuart -

[xSpace]

Another excellent paper is the Wyle report, from Wyle Laboratories, dated 1973. WR73-5R. Not sure where to download that, but I'm sure it will turn up somewhere if you Google it.

It is the last link on the bottom of this page @ buildthisroom.com:
A Study of Techniques to Increase Sound Insulation of Building Elements
Wyle WR 73-5R (3 leaf panel)

[Soundman2020]

Thanks Brien! I should have known that you'd have a link to it on your web site.


- Stuart -

[G-Sun]

It is the last link on the bottom of this page @ buildthisroom.com:
A Study of Techniques to Increase Sound Insulation of Building Elements
Wyle WR 73-5R (3 leaf panel)

Thanks!

[Carl Hungus]

Soundman,

Thanks for replying to to my questions. Just curious, it seems like the bottom stud plate would have to be driven securely into the slab, but would it benefit the walls to have some kind of neoprene or rubber matting between the bottom plate and the slab? My slab continues to the outside wall, and Rod's book makes it seem as though sound through the slab if its on earth isn't as a big of a flanking issue, but I want to be sure there isn't something more I can do. My slab is detached from other buildings and is about 100mm thick.

thanks!

[Soundman2020]

Just curious, it seems like the bottom stud plate would have to be driven securely into the slab, but would it benefit the walls to have some kind of neoprene or rubber matting between the bottom plate and the slab?

There are methods for doing that, often referred to as "floating" the wall, but it isn't easy to get right. The main issue is that, as you point out, the sole plate does have to be firm anchored to the slab, so just putting rubber underneath won't help since you still need to nail, screw or bolt through that rubber, thus destroying the decoupling you achieved with the rubber. There are special rubber sleeves or collars that can be used to isolate the anchor bolts, but that just adds expense for debatable benefits. But the biggest issue is actually getting the wall to "float" in the first place. The rubber has to be "squashed" by just the right amount in order for that to happen. If you don't "squash" it enough, then the wall isn't floating and sound will still flank though the rubber. And likewise, if you "squash" the rubber too much, then the wall isn't floating either, and sound will still flank though the rubber. So you have to get that just right.

Every type of rubber has different characteristics, which state how much deflection (degree of "squashing") you will get for a certain load, and how much deflection you need in order for it to float. So you need to figure out the weight of the wall fairly accurately, so that once it is built it will squash the rubber just right. If you get your calculations wrong, or have to add or remove weight during the build for whatever reason, then your wall won't float.

So you have to use the right type of rubber, cut to the right shape and size, then load the wall the right way, and also carefully use the bolts and collars, all in perfect symphony, to get your wall to float. It can be done, but takes a lot of effort and some extra money to do right. And as Rod points out, the benefit might not be worth it anyway, if you are building your room on a good slab-on-grade. Unless you need extreme levels of isolation, it probably just isn't worth the time and effort. That would be far better spent in other areas of the build, where the benefits can be drastically greater, such as in good isolation on your doors, windows, HVAC and electrical.

That said, rubber under the sole plate can still be useful for another reason: to seal the gap better. If your concrete slab is uneven, pitted, cracked or in poor condition, then a layer of rubber can help to get a good seal under the sole plate, which is very, very important. It won't float your wall, but will improve the isolation by just sealing that gap airtight. But here too, if your slab is level, flat and in good condition, then simply sealing with acoustic caulk is plenty good enough.

- Stuart -

[RJHollins]

Another excellent paper is the Wyle report, from Wyle Laboratories, dated 1973. WR73-5R. Not sure where to download that, but I'm sure it will turn up somewhere if you Google it.

It is the last link on the bottom of this page @ buildthisroom.com:
A Study of Techniques to Increase Sound Insulation of Building Elements
Wyle WR 73-5R (3 leaf panel)

Thanks for the link 'xSpace' !

[Carl Hungus]

Thanks for the detailed reply Stuart. Sounds like its far to much hassle to float the walls for the type of studio I'm building. Also doing the first layer in wood for stability is a great suggestion, I hadn't thought of that.
Are these good examples of the sway braces for the top plate you mentioned earlier?:

http://www.kineticsnoise.com/arch/psb.html

[Soundman2020]

Are these good examples of the sway braces for the top plate you mentioned earlier?:

Looks like they might work. Also try Mason Industries: they seem to have a good range.


- Stuart -