Brick Inner Leaf. Advantages and Disadvantages?

[Skai_Penalva]

Hello good peoples!

I am currently in my research phase for my new studio build. I have no designs drawn up yet since I am still trying to get a better understanding of certain concepts before I even get to the drawing board. All I have right now is the land and ideas in my head.

The studio will be located in a residential area in a very quiet part in the outskirts of the city, up in the mountain so I really need good isolation. Mostly because I plan on recording rock bands, so I want them to feel confident in playing as loud and as late as they want.

I own a plot of land where I will be building the studio. The terrain is slanted so I was thinking about having the studio "underground". Not fully, but maybe just having the front wall exposed and having the rest covered over by the land. (I hope I am being clear). My outer leaf will be a stone wall since in order to do the studio underground, they need to build a thick slanted wall for geological reasons. Anyway, I am digressing. I can do a separate thread on this topic alone if that's more convenient. My actual post about this build will come later with much more detail including pictures, design and such. Right now I just want to do proper research about doing my inner leaf with red brick or concrete brick for isolation purposes in stead of drywall.

I have tried using the search tool for this specific topic but I cannot find what I'm looking for. If you can redirect me to any posts that explain these things or any article I can read to learn more I would deeply appreciate it.

1. I want to know the advantages and/or disadvantages of building the inner leaf walls with red brick or concrete brick as far as isolation and treatment goes and if it is better than drywall. In my country I believe this type of work is cheaper than drywall and wood studs. Besides 2x4 wood studs are not common here, they only use 2x2 studs which I have been told in other of my posts is not recommended at all because it is not rigid enough. This is what I did in my current project studio room and my isolation is not great (no complaints from neighbors, but still not great). I saw that @John has a studio on his portfolio where the inner walls are all concrete brick. I tried reaching out but have not yet gotten a reply, so I am turning to posting my own thread about it.

http://www.johnlsayers.com/Pages/lovestreet.htm

2. I could just do the live room's inner leaf with bricks or stone for a livelier sound?

3. My other concern is regarding design, but I can wait until I do my thread to dive deeper into this topic. I wanted to know if I'd have to build the room with parallel walls and then do the splayed walls for the RFZ design with the treatment inside, with resonator slats and soffits and such.

Thank you for your time and your help! Have a great day everyone!

- Skai

[Paulus87]

Hello good peoples!

I am currently in my research phase for my new studio build. I have no designs drawn up yet since I am still trying to get a better understanding of certain concepts before I even get to the drawing board. All I have right now is the land and ideas in my head.

The studio will be located in a residential area in a very quiet part in the outskirts of the city, up in the mountain so I really need good isolation. Mostly because I plan on recording rock bands, so I want them to feel confident in playing as loud and as late as they want.

I own a plot of land where I will be building the studio. The terrain is slanted so I was thinking about having the studio "underground". Not fully, but maybe just having the front wall exposed and having the rest covered over by the land. (I hope I am being clear). My outer leaf will be a stone wall since in order to do the studio underground, they need to build a thick slanted wall for geological reasons. Anyway, I am digressing. I can do a separate thread on this topic alone if that's more convenient. My actual post about this build will come later with much more detail including pictures, design and such. Right now I just want to do proper research about doing my inner leaf with red brick or concrete brick for isolation purposes in stead of drywall.

I have tried using the search tool for this specific topic but I cannot find what I'm looking for. If you can redirect me to any posts that explain these things or any article I can read to learn more I would deeply appreciate it.

1. I want to know the advantages and/or disadvantages of building the inner leaf walls with red brick or concrete brick as far as isolation and treatment goes and if it is better than drywall. In my country I believe this type of work is cheaper than drywall and wood studs. Besides 2x4 wood studs are not common here, they only use 2x2 studs which I have been told in other of my posts is not recommended at all because it is not rigid enough. This is what I did in my current project studio room and my isolation is not great (no complaints from neighbors, but still not great). I saw that @John has a studio on his portfolio where the inner walls are all concrete brick. I tried reaching out but have not yet gotten a reply, so I am turning to posting my own thread about it.

http://www.johnlsayers.com/Pages/lovestreet.htm

2. I could just do the live room's inner leaf with bricks or stone for a livelier sound?

3. My other concern is regarding design, but I can wait until I do my thread to dive deeper into this topic. I wanted to know if I'd have to build the room with parallel walls and then do the splayed walls for the RFZ design with the treatment inside, with resonator slats and soffits and such.

Thank you for your time and your help! Have a great day everyone!

- Skai

If you can build your inner and outer leaves from brick/concrete then that's excellent, the more mass and more air gap (insulated) the better the isolation. Of course, you'll need to match the surface density for each leaf on the ceiling/roof, too.

For your second question, it depends on your design criteria. I am no longer a fan of authentic geometric RFZ designs, and in my opinion it is better to build completely rectangular "bunkers" for the outer and inner leaves. Treatment layers may or may not be angled depending on purpose, but, if you have no constraints on size then rectangular rooms provide the most room volume, easier to construct, more predictable modal response, usually easier to treat and cheaper. I am a fan of non environment, FTB and balanced non environment rooms as a basis for design criteria. These can all be built in rectangular bunkers.

I hope this helps,
Paul

[Skai_Penalva]

I hope this helps,
Paul

Hey Paul, it does help a lot! But of course, as always, it raises more questions!

Of course, you'll need to match the surface density for each leaf on the ceiling/roof, too.

Yes, in that case the ceiling/roof would be slabs of concrete, outer and inner.

Here are my new questions:

1. Would brick inner walls provide better isolation than a double layer of drywall/2x4 wood studs/R-13 Fiberglass?

If you can build your inner and outer leaves from brick/concrete then that's excellent, the more mass and more air gap (insulated) the better the isolation.

2. Regarding the air gap in between the walls, what would be an appropriate distance?

3. When you say insulation, you mean in between the brick walls inside the air gap? I have access to R-13 and R-19 type fiberglass insulation. The fluffy kind that comes in rolls. Would this be good? Would both walls need it? I'm guessing it would be glued on, right? Would it be a layer on the inside of the outer wall, and another layer on the outside of the inner wall?

4. Would I need to decouple the concrete slab floors on each room from each other? I mean, make separate concrete slabs for each room. Or would one whole concrete slab for the entire building be OK?

5. Would I have to match the surface density on the doors as well?

For your second question, it depends on your design criteria. I am no longer a fan of authentic geometric RFZ designs, and in my opinion it is better to build completely rectangular "bunkers" for the outer and inner leaves. Treatment layers may or may not be angled depending on purpose, but, if you have no constraints on size then rectangular rooms provide the most room volume, easier to construct, more predictable modal response, usually easier to treat and cheaper. I am a fan of non environment, FTB and balanced non environment rooms as a basis for design criteria. These can all be built in rectangular bunkers.

6. Why are you no longer a fan of RFZ designs? I mean besides practicality when building. Wouldn't the thickness of the brick walls allow for lower frequencies to be reflected to the back of the control room? Would it be more problematic to treat than a parallel rectangular room? I don't really understand why, if you could elaborate I'd be grateful.

Thank you, Paul!

[Paulus87]

Here are my new questions:

1. Would brick inner walls provide better isolation than a double layer of drywall/2x4 wood studs/R-13 Fiberglass?

Yes, much much better.

2. Regarding the air gap in between the walls, what would be an appropriate distance?

Depends how much isolation you need, but if both leaves are 8" concrete block then even a gap of 4" will provide excellent isolation all the way down to 20Hz, increase this to 12" and you'll have near-enough silence, if built correctly. But you probably don't need such extreme isolation in all honesty.

3. When you say insulation, you mean in between the brick walls inside the air gap? I have access to R-13 and R-19 type fiberglass insulation. The fluffy kind that comes in rolls. Would this be good? Would both walls need it? I'm guessing it would be glued on, right? Would it be a layer on the inside of the outer wall, and another layer on the outside of the inner wall?

Yes in terms of reaching your isolation goals, there is no need to use anything more than the cheapest of the fluffiest, you will not gain anything from denser insulation in the cavity. And you should fully fill the cavity, so there is no actual gap, the insulation is the "air gap". However, for building code purposes you might need to use an insulation that has a certain R value, you'll have to check. In which case you might have to mix the types of insulation you use in order to pass inspection.

4. Would I need to decouple the concrete slab floors on each room from each other? I mean, make separate concrete slabs for each room. Or would one whole concrete slab for the entire building be OK?

It is rarely needed unless there are train tracks, airports or other sources of extreme noise/vibration near by. So you wouldn't need to have separate slabs, however, if maximum isolation is your goal then you can build separate slabs. You could even build separate slabs for each leaf, so your control room would have the main slab for your inner leaf and then a separate perimeter slab for the outer leaf, and the same for your tracking room. You leave a gap between the slabs and fill the gap with a resilient expansion joint. But that is really very extreme.

5. Would I have to match the surface density on the doors as well?

Ideally yes. But you can achieve it in a different way: maximise the air gap between the inner and outer doors to make up for the doors having less surface density than the walls/ceiling. You can play with Gregwor's MSM TL Calculator to see what kind of isolation you can expect from different assemblies:
https://docs.google.com/spreadsheets/d/ ... 1543869474
You'll need to "save as a copy" first before you can enter values.

6. Why are you no longer a fan of RFZ designs? I mean besides practicality when building. Wouldn't the thickness of the brick walls allow for lower frequencies to be reflected to the back of the control room? Would it be more problematic to treat than a parallel rectangular room? I don't really understand why, if you could elaborate I'd be grateful.

This is personal preference more than anything, but for an accurate mixing environment I do not see that there is any advantage to having a diffuse return of sound coming back to the listening position. I prefer dual environment mixing rooms: one environment for the loudspeakers and another for the operator(s). This means you hear the direct sound coming from the speakers with zero influence from the room, but to put your subconscious at ease you still hear your own self noise cues from cleverly placed reflective/diffusive surfaces that do not interact with the loudspeakers. It is really the best of both worlds.

Also, no matter how dense your RFZ walls are you are still limited to what frequency range you can deflect away from the listening position since LF will not "see" the angles of typical RFZ walls. But the criteria for RFZ really concerns only those frequencies responsible for giving the illusion of a stereo field, i.e. 1kHz-8kHz, though some designers also go down lower if they can.

If you like RFZ design then go for it, I will still help you to design it (and hopefully others).

One thing to remember; if you are going to build your inner leaf from concrete/brick then it will likely require more, and perhaps more complicated treatment than a drywall assembly would. This is because your inner space will be incredibly reflective all across the frequency spectrum since less sound will escape through the walls. This means you will most likely need to use membrane traps in order to deal with low frequency issues. Not a big deal, just something to be aware of in the design stage, since you'll want to optimise your room dimensions in order to give you the best modal spread to begin with.

Paul

[DanDan]

You could make the outer leaf brick, and a decoupled inner leaf of plasterboard on springy studs. Good start at lower LF absorption.

[Paulus87]

I concur with DanDan, if you do not need the absolute highest degree of isolation then you will still achieve an excellent level of isolation with the method he described with the additional benefits of creating what is effectively large membrane traps all the way round your room(s). This will help absorb very low frequency and make the rest of the space easier to treat. This is a technique utilised by Newell Acoustics more often than not, amongst other well known studio designers.

Paul

[Skai_Penalva]

DanDan, thank you for your answer!

The outer leaf will definitely be stone. The studio will be constructed to be underground. I have the land right now and it has a good inclination towards the edge. The basic idea is to dig back into it and have the outer leaf totally backed by rock and dirt all around. The ceiling will be a concrete slab. A house will be constructed on top of it.

After talking with the head engineer he said brick or concrete walls would be cheaper, but in the long run more problematic. I would not be able to make any modifications or inner repairs regarding electricity or HVAC systems. It would all become just more complicated than drywall. So I will be building with drywall. I will look into decoupling the plasterboard inner leaf on springy studs. I am not familiar with this method.

I really do need very effective isolation since the studio is in a residential area in the outskirts of the city, where there is not much ambient noise so it's a pretty peaceful place. I'm confident the sound transmission won't be too much of a problem, but I do want a good level of isolation from in between rooms inside the studio. Not the absolute highest, but surely good enough to be able to track drums and monitor the recording without worrying about bleeding from the live room.

Do you have any examples of this type of wall build on springy studs or links I can check out? I'm not seeing anything specific on their website.

Do you mean decouple the walls from the floor?

[Paulus87]

DanDan, thank you for your answer!

The outer leaf will definitely be stone. The studio will be constructed to be underground. I have the land right now and it has a good inclination towards the edge. The basic idea is to dig back into it and have the outer leaf totally backed by rock and dirt all around. The ceiling will be a concrete slab. A house will be constructed on top of it.

After talking with the head engineer he said brick or concrete walls would be cheaper, but in the long run more problematic. I would not be able to make any modifications or inner repairs regarding electricity or HVAC systems. It would all become just more complicated than drywall. So I will be building with drywall. I will look into decoupling the plasterboard inner leaf on springy studs. I am not familiar with this method.

I really do need very effective isolation since the studio is in a residential area in the outskirts of the city, where there is not much ambient noise so it's a pretty peaceful place. I'm confident the sound transmission won't be too much of a problem, but I do want a good level of isolation from in between rooms inside the studio. Not the absolute highest, but surely good enough to be able to track drums and monitor the recording without worrying about bleeding from the live room.

Do you have any examples of this type of wall build on springy studs or links I can check out? I'm not seeing anything specific on their website.

Do you mean decouple the walls from the floor?

If you build independent slabs then you really do not need to decouple the studs from the floor to achieve the highest isolation. As long as the inner leaf floor, ceiling and walls are completely detached from the outer leaf then that's all that matters.

Paul

[Skai_Penalva]

I don't think I can build independant slabs but I'll ask the engineer if this is a viable option.

In case this is not possible, how do I effectively decouple de inner walls from the floor?

[Paulus87]

I don't think I can build independant slabs but I'll ask the engineer if this is a viable option.

In case this is not possible, how do I effectively decouple de inner walls from the floor?

If it was me, I wouldn't bother. All of the solutions which do not cost a fortune are not worth the cost/effort. You could put some rubber on the bottom of the sole plates, but this won't isolate much at all but what it will do is provide a nice air tight seal and fill in all the imperfections in the wood and the concrete.

You will still get excellent isolation, the mass of the concrete is huge and it will be infinitely damped by the earth, this will completely minimise any potential transmission to the point where it doesn't matter anymore, I really think you won't be disappointed.

Paul

[Skai_Penalva]

Paul, this is great to know!

I had a talk with my structural engineer and he said it would be no problem at all to do the isolated slabs. In fact, it would even be slightly cheaper for him. Being this the case, is it worth it to do it? His only uncertainty was what kind of material the gap in between the slabs would require. He mentioned expansion joints and some kind of foam. Does this sound correct? I noticed you mentioned this in your thread but I don't think you mentioned which method you chose in the end.

He also thought the studs on springs would be a viable option.

I think if it's beneficial acoustically (even if just slightly), cost effective and not a problem for the builders, then it would be worth it. If I can do both, would this be beneficial? According to the engineer, this would all be fairly easy. He was not worried at all by any of it.

You've given me plenty of confidence that whatever we decide to do will yield good results! Thank you!

We are a looooong way before building. We will do all the research and design possible before we even begin to prepare the land.

[Paulus87]

Paul, this is great to know!

I had a talk with my structural engineer and he said it would be no problem at all to do the isolated slabs. In fact, it would even be slightly cheaper for him. Being this the case, is it worth it to do it? His only uncertainty was what kind of material the gap in between the slabs would require. He mentioned expansion joints and some kind of foam. Does this sound correct? I noticed you mentioned this in your thread but I don't think you mentioned which method you chose in the end.

He also thought the studs on springs would be a viable option.

I think if it's beneficial acoustically (even if just slightly), cost effective and not a problem for the builders, then it would be worth it. If I can do both, would this be beneficial? According to the engineer, this would all be fairly easy. He was not worried at all by any of it.

You've given me plenty of confidence that whatever we decide to do will yield good results! Thank you!

We are a looooong way before building. We will do all the research and design possible before we even begin to prepare the land.

Yes it will be beneficial if done correctly - yes you can use spray foam in the gap and rubber expansion joint to seal it.

Studs on springs - what kind of springs? I can't see this being beneficial tbh and may even make things worse since you would need to find a way of properly sealing it airtight. Let us know the details of the springs and we can advise you further.

Paul

[Skai_Penalva]

I concur with DanDan, if you do not need the absolute highest degree of isolation then you will still achieve an excellent level of isolation with the method he described with the additional benefits of creating what is effectively large membrane traps all the way round your room(s). This will help absorb very low frequency and make the rest of the space easier to treat. This is a technique utilised by Newell Acoustics more often than not, amongst other well known studio designers.

Paul

Regarding the studs on springs, I was going about what you and DanDan recommended. I am not certain what method he is describing here. You mentioned Newell Acoustics but I could not find any information on this method in their website or in this forum. Could you please describe this method?

[Paulus87]

I concur with DanDan, if you do not need the absolute highest degree of isolation then you will still achieve an excellent level of isolation with the method he described with the additional benefits of creating what is effectively large membrane traps all the way round your room(s). This will help absorb very low frequency and make the rest of the space easier to treat. This is a technique utilised by Newell Acoustics more often than not, amongst other well known studio designers.

Paul

Regarding the studs on springs, I was going about what you and DanDan recommended. I am not certain what method he is describing here. You mentioned Newell Acoustics but I could not find any information on this method in their website or in this forum. Could you please describe this method?

Ah I see,

What I am describing is simply stud walls with layers of drywall, and perhaps some bitumen deadsheets between the drywall panels. There are no springs on the studs, the sole plates just bolt down onto the slab.

I believe DanDan is describing the same method, and by "springy" he simply means timber studs? Maybe I am wrong, I'll let DanDan explain more if so.

Paul

[Skai_Penalva]

Oh yes of course! 2x4 timber studs I suppose.

This is all very helpful. I am ready to move on to the design phase. I'll be starting a separate thread for this once I have an initial design ready.