John Sayers' Recording Studio Design Forum Archive

Hi everyone !

First of all, spending time here, I’ve read and learn a lot and I would like to salute all of you for giving so much advices, informations and help for guy like me. It’s great to see this kind of initiative here, so many thanks for your time and support !

To introduce myself, I’m Sebastien a french guy from a small town near Lille, (sorry for my broken english), I’m in a project of building a drummer room in a house I just moved in, where I would like to practice and record. It will be in an outbuilding just against my house.

My purpose is to soundproof the room to not disturb my neighboor, his garden is next to the wall and his house is 20 meters further behind this room. I would like to practice late at night and him not to hear anything. I hope this is not mission impossible...

I’m gonna build it by myself, and I want to do it the right way so could you help me ? I’ve read threds here for hours, but still need help for some specific questions and some old ressources and links that became unaviable now (broken links, pictures not hosted anymore...).
For now, here is the plan of the present-day room : Things I’ve read, know and want to check :

I plan a room in a room, mass-spring-mass principle with 2 leaves (the most efficient as I’ve read here) and a sas with two doors. It’s sized L3.25m*W3.20m*H2.25m, so I don’t have much place, but want to do it as efficient as I can.

For now, there are two doors and one window. I think I’ll bick up the window and the door next to the garage to keep only 1 aperture and get minimal sound leakage. Speaking of that, this room has a cut corner were I think there was an old chimney flue. An old piece of it is still on the roof, I will tear it down.
I think i’m not going to need a floating floor, since it’s a concrete slab on the ground, right ? So I’m going to build a drum riser, so if you have any advice on this

Things I don’t know or need help :

1. 1. This room is made of 4 true walls, I think two of bricks and 2 of blockwork with an aerated concrete frame against but I don’t know if there is insulation in between. Anyway, I’ve read here it would be better to remove all of this aerated concrete to put insulation and make my new leaf, so I certainly will recover some centimeters compared to the schema above. For this new leaf, what would be the best ? I was thinking to bluid a wooden framing with multiple layers of gypsum boards on it (how many, 2, 3 ? How thick ?) on an OSB/plywood layer. But maybe there is more efficient, like blockwork leaf instead ?

Here is what I thought about : If the wooden framing is the right way :

1. 2. What would be the ideal size (width and thickness) of the wooden parts of the frame to support all the weight? (I have a contact in a sawmill that could cut to the sizes I need)

1. 3. How many air space in between the two leaves do you recommend in my case ? The wooden framing is included in that space, whatever its size, right ?

1. 4. Should I fill this entier space gap with insulation wool or let a gap without anything but air ? What kind of insulation would you recommand ? Glass, rock wool (soft or solid panel ?) ?, wood fiber, hemp fiber ? I think I saw on a thread here 50kg/m3 for rockwool or 30kg/m3 for fiberglass, but what would be the best choice ?

1. 5. Would you put anything resilient between the ground and the new framing, or wood and gypsum boads direcly on the floor with just acoustic seal ? For now there is floor tiles on the floor, should I remove it ? I assume you recomand carpet to cover the floor ?

1. 6. Should I use Greenglue between layers of gypsum boards ? Would it be significant ?

1. 7. Should I use resilient channels to screw gypsum boards on the framing or should I screw boards directly on the framing ? (or maybe on not resilient channels ?)

1. 8. Would you use special acoustic sealer between boards or standard silicon seal is sufficient ?

1. 9. For now, I don’t know how the ceilling is made. I think there are wooden joists above the suspended gypsum boards but not sure, the space under the roof is not very easy to access… So I was thinking to remove the existent gypsum boards of the ceiling to make a dense frame above supported by the joists. Any ideas ? Because I really don’t know what to do about that. I don’t want this ceiling to be a sound weakness… I heard about making a concrete slab, is it concievable in my case ?

Anyway :

1. 10. Against humidity and moisture, would you put a vapor barrier ? On witch frame ? The two rooms against will not be heated, but this studio will. I would like to have a stable temperature and humidity level inside so I’m thinking about a HVAC/air extractor, but don’t really know were to place air input and output and what kind of device.

1. 11. Keeping in mind the narrow dimensions I have and in order to get a great acoustic inside the room ; should I build the inside room with another ratio rather than fit the entire available space ?
   For the budget, I thought about 5000€ without the wood, but with time and patience, I can increase it.

I know this is a lot of questions but needed to start. I think I will have some more after beginning… I’m thinking about making a video of all the steps of the project and maybe make a video tutorial with it to help people in my language, if you agree with of course !
When I will have find the way to reduce de size of the actual room photos, I will post them below

So many thanks !
Musically,
Sebastien

Hello !

I figured out I forgot to say how loud I am : about 110dB I think. The insulation goal would be as efficient as possible.

So as promised, here are some photos of the room :
The outbuilding is on the left, under the red sign, my house is behind. On the right, this is my neighbor's house and his garden in between.

Here is the room from the outside, from my garden's side. On the left, this is a veranda. As you ca see, there are some pipe holes to stop/block (I don't know the english word ).

Here is a view of the room from the garage. This is the one I'm going to brick up.

All the best,
Seb

Hi Sebastien, and Welcome!!

I would like to practice late at night and him not to hear anything. I hope this is not mission impossible...

It can be done! It might not be easy or cheap, but it is possible.

For now, there are two doors and one window. I think I’ll bick up the window and the door next to the garage to keep only 1 aperture and get minimal sound leakage.

Good start!

think i’m not going to need a floating floor, since it’s a concrete slab on the ground, right ?

Right! http://www.johnlsayers.com/phpBB2/viewt ... f=2&t=8173

Anyway, I’ve read here it would be better to remove all of this aerated concrete to put insulation and make my new leaf, so I certainly will recover some centimeters compared to the schema above.

Careful with that! Before you remove anything, check with a structural engineer to make sure you are are not causing any damage to load-bearing structures!

I was thinking to bluid a wooden framing with multiple layers of gypsum boards on it (how many, 2, 3 ? How thick ?) on an OSB/plywood layer.

How much isolation do you need, in decibels?

2. What would be the ideal size (width and thickness) of the wooden parts of the frame to support all the weight? (I have a contact in a sawmill that could cut to the sizes I need)

Probably standard 2x4 studs would do the job perfectly. Those probably measure around 40mm x 90mm, in metric. That's for the studs: for the ceiling joists, you'll need to get a structural engineer to tell you what size you will need to safely carry the load you plan to put up there.

3. How many air space in between the two leaves do you recommend in my case ?

How much isolation do you need, in decibels, and what frequencies do you need it at?

The wooden framing is included in that space, whatever its size, right ?

Correct.

4. Should I fill this entier space gap with insulation wool

Yes, definitely!

What kind of insulation would you recommand ? Glass, rock wool (soft or solid panel ?) ?, wood fiber, hemp fiber ? I think I saw on a thread here 50kg/m3 for rockwool or 30kg/m3 for fiberglass, but what would be the best choice ?

There is a slight advantage to 50kg/m3 mineral wool, but 30 kg/m3 fiberglass also works very well.

5. Would you put anything resilient between the ground and the new framing,

Only caulk, to seal the gap air-tight. As you put down the sole plate, also put down three beads of good-quality caulk: one right down the middle of the sole plate, and the other two about 2cm each side of that. Then put it in place, and put the bolts through it, into the slab, then tighten them. Then run another bead of caulk along the two edges. And one more bead under the bottom of each layer of drywall.

For now there is floor tiles on the floor, should I remove it ?

depends on the type of tile. Ask your structural engineer if you need to remove that before building the walls.

I assume you recomand carpet to cover the floor ?

Nope! Never. Carpet is a very bad choice for studio floors, which is why you never see carpet on the floor of professional studios!

6. Should I use Greenglue between layers of gypsum boards ? Would it be significant ?

If you can afford it, then yes. It does work, especially for low frequencies.

7. Should I use resilient channels to screw gypsum boards on the framing

No. You don't need RC if the framing is fully decoupled form the outer-leaf walls and ceiling.

8. Would you use special acoustic sealer between boards or standard silicon seal is sufficient ?

You only need to caulk places where there could be air gaps, which is around the edges of the entire wall. You don't need to caulk between the individual panels of drywall. Just "mud and tape" each layer, as for any normal wall.

For those places where you do need to caulk, it is best to use a high quality, very flexible caulk that does not harden, shrink or crack. It must remain rubbery and soft, even when it is fully dry.

So I was thinking to remove the existent gypsum boards of the ceiling to make a dense frame above supported by the joists.

Here too you need a structural engineer to check the load-carrying capacity of your existing joists for the outer leaf, as well as the new ones on the inner-leaf.

10. Against humidity and moisture, would you put a vapor barrier ? On witch frame ?

The vapor barrier always goes inside the cavity, against the warmest surface. Usually, that is the inner-leaf, but it depends on climate.

I know this is a lot of questions but needed to start.

I figured out I forgot to say how loud I am : about 110dB I think.

OK. Now you just need to figure out "how quiet you need to be", then based on those two numbers, you can do the math to figure out how much isolation you need.

- Stuart -

Many thanks for your reply and those advices, really appreciated !! Here are some precisions :

How much isolation do you need, in decibels, and what frequencies do you need it at?
OK. Now you just need to figure out "how quiet you need to be", then based on those two numbers, you can do the math to figure out how much isolation you need.

The kick would be my lowest frequency and I assume my biggest problem, about 60-80Hz I think.
I’m loud about 110dB, 50dB (maybe 45) would be acceptable outise of the room, in neighbours garden. So the isolation needed would be about 60-65dB, witch sounds pretty huge :/
So how many air space and gypsum boards/OSB thickness would you recommand ?

Nope! Never. Carpet is a very bad choice for studio floors, which is why you never see carpet on the floor of professional studios!

Ok ! What do you recommand ? Some wooden parquet or maybe vinyl linoleum ?

check with a structural engineer to make sure you are are not causing any damage to load-bearing structures!

You’re right, I’m going to check it out with a specialist to be sure to not do any big mistake !

If you can afford it, then yes. It does work, especially for low frequencies.

The bucket of 18.9L is 269€ in France (295$US) and tube of 0.828L about 16€ (17.6$US) I just saw an official GreenGlue calculator right here : http://www.greengluecompany.com/products
So I’ll probably need between 36 and 48 tubes or 2 buckets so 540€ (594$US). So with you advice, this is reasonnable for me, let’s greenglue it !

For those places where you do need to caulk, it is best to use a high quality, very flexible caulk that does not harden, shrink or crack. It must remain rubbery and soft, even when it is fully dry.

I saw the Green Glue Noiseproofing sealent wich is 10€ per tube, so not expensive at all. I assmue this is a good caulk for what I want to do ?

The vapor barrier always goes inside the cavity, against the warmest surface. Usually, that is the inner-leaf, but it depends on climate.

Here in noth of France we have an oceanic climate with cool summers and cool winters. With an average of 11°C (52°F) and 700mm of rain per years. So in my case and with my sketch, this vapor barrier would be between the OSB pannel and the wooden framing/wool right ?

Two more questions if you don’t mind :

12. I’m searching for two good insolating doors french dealer but it’s not very easy. Admitting I need a 60-65dB insolation, I was wondering how many indicative noise reduction I had to go for each door. I suppose this is more complicated than it seems to be :/

13. I’m inquiring about HVAC and ventilation. Before finding the solution, where would you place the air input and output ?
As a reminder, this room is between a garage and a storeroom + hallway, there is no up floor, only a tiled roof. I can’t drill a hole on the neighboor side wall, but it could be easily done on my garden side.

HUGE thanks !

So the isolation needed would be about 60-65dB, witch sounds pretty huge :/

Yep! That's a lot. It is possible to get that much isolation, but pretty hard to do for a home studio, and pretty expensive.

So how many air space and gypsum boards/OSB thickness would you recommand ?

To get that type of isolation, you'd probably need a surface density of around 60 kg/m2 or more on each leaf, and an air gap of around 25cm or so.

Ok ! What do you recommand ? Some wooden parquet or maybe vinyl linoleum ?

Plain concrete is good! Or laminate flooring, over a suitable underlay. There are some really good looking laminate flooring systems these days, and they go in fast and easy.

So with you advice, this is reasonnable for me, let’s greenglue it !

Great! If it fits your budget, then it certainly will help with isolation, especially in the low end.

I saw the Green Glue Noiseproofing sealent wich is 10€ per tube, so not expensive at all. I assmue this is a good caulk for what I want to do ?

The problem that I've had with their sealant (caulk) is that it shrinks when it dries, and can crack, so you often need to go over it a second time. It's probably better to go for a caulk that does not shrink. The GreenGlue compound itself is fantastic, and I highly recommend it. Not so much their caulk.

Here in noth of France we have an oceanic climate with cool summers and cool winters. With an average of 11°C (52°F) and 700mm of rain per years. So in my case and with my sketch, this vapor barrier would be between the OSB pannel and the wooden framing/wool right ?

Right.

12. I’m searching for two good insolating doors french dealer but it’s not very easy. Admitting I need a 60-65dB insolation, I was wondering how many indicative noise reduction I had to go for each door. I suppose this is more complicated than it seems to be :/

Yep! Getting 60 dB of isolation from a door system is a Very Big Deal!! It can be done, but is not easy. You can build the doors yourself, though.

Here's what one of my customers in Australia did recently:
I designed that door system for 55 dB of isolation, and he's getting a bit more than that. But there are triple seals on both of those doors, and they are built up from several layers of solid wood. You can imagine how heavy they are by looking at the size and number of hinges... They are massive. That's why I put the automatic door closers on there: it's not safe to try to close such a heavy door by hand. The automatic closer does it smoothly and gently.

So it is possible to get high levels of isolation from doors, but it takes careful design and careful workmanship, and you need lots of mass and lots of seals.

13. I’m inquiring about HVAC and ventilation. Before finding the solution, where would you place the air input and output ?

I prefer to put the air supply vents at the rear of the room, on the ceiling or rear wall, and the air return vents on the ceiling at the front of the room. That tends to give good air flow throughout the entire room.

But there's a lot of calculations that you'll need to do, to get the HVAC designed!


- Stuart -

Yep! That's a lot. It is possible to get that much isolation, but pretty hard to do for a home studio, and pretty expensive.

I don’t fear to do it the right way, so let’s do this as efficient as we can !

check with a structural engineer to make sure you are are not causing any damage to load-bearing structures!

According to your advices, a specialist is coming to the house to check those points in a few hours !

To get that type of isolation, you'd probably need a surface density of around 60 kg/m2 or more on each leaf, and an air gap of around 25cm or so.

25 cm is acceptable for me, if the aerated concrete is removable, I can get 10cm back. So I have to take an additional 15cm on each side from the current size.

If I understood correctly, my leaf (OSB + Gypsum board + phonic gypsum board) must have a total density of 60kg/m2 ? OSB 1.8cm thick is 22kg/m2 Gypsum board 1.25cm thick is 9.3kg/m2 and phonic gypsum board 1.25cm thick is 11.8kg/m2. So on my plans, if i’m not mistaking I have 22+9.3+11.8=43.1kg/m2. Conclusion, I need to add an extra 4th layer to get those 17kg/m2, right ?

The problem that I've had with their sealant (caulk) is that it shrinks when it dries, and can crack, so you often need to go over it a second time. It's probably better to go for a caulk that does not shrink. The GreenGlue compound itself is fantastic, and I highly recommend it. Not so much their caulk.

Haha, it would have been too easy Ok, I’ll be searching for a good not shrinking caulk ! Do you recommend some specific brands that would be sold by chance in France ?

Yep! Getting 60 dB of isolation from a door system is a Very Big Deal!! It can be done, but is not easy. You can build the doors yourself, though.

What a great job ! Those doors are awsome ! Nevertheless, it would be easier because I don’t need a window in it, but I don’t know if I’m able to do such a job, with the accuracy required, especialy without building instructions…

My future doors doesn’t lead to the outside, but in a closed hallway with an additional door, making an other sas with some square meters (maybe 5). Silence in the hallway isn’t required. Because of that, it is possible to lower the doors sytem efficiency ?

Getting a Rw of 30dB for each door would be enough you think ?

One of those doors need to be locked, I suppose I’ll need to drill some holes in it, or maybe it’s avoidable ?

I prefer to put the air supply vents at the rear of the room, on the ceiling or rear wall, and the air return vents on the ceiling at the front of the room. That tends to give good air flow throughout the entire room.

But there's a lot of calculations that you'll need to do, to get the HVAC designed!

For now, I’m investigating on a ventilation (Incoming + outgoing) + deshumidifier. But I don’t know if the room will not warm up too fast…


Many thanks again Stuart !

I have some news to add !
I checked with a specialist the 3 points you mentioned. Some really good news here !

First of all, he told me it was preferable to remove the floor tiles. Not a bad thing if I want to keep a plain concrete finish on the floor. I prefer laminate flooring but it’s fine too, it’ll depend on the cost.

The aerated concrete (ytong) layer seems not to support anything. Without any bad surprise, it would be fully removable ! I can take back those precious 10cm to make the 25cm air space without taking much surface

The other good news is : I have a concrete slab ceiling reposing on the brick walls. I’ll have less work to do as I expected on this point. This is pretty surprising as there is no place to make another floor under the roof... I take it ! All I have to do is to remove the existing gypsum board 5cm below.
So the ceiling is made of (from the top to the bottom) as you can see on the picture below :
10cm of fiberglass
1 layer of concrete slab
1 layer of daub board or earthy board (I don’t know the right term) right against the concrete slab
A space gap of about 5cm with some fiberglass
1 layer of gypsum boards

I want to keep a plain concrete finish on the floor. I prefer laminate flooring

The aerated concrete (ytong) layer seems not to support anything. Without any bad surprise, it would be fully removable ! I can take back those precious 10cm to make the 25cm air space without taking much surface

Check with your structural engineer about that. If you need that extra space, and you can get it safely, then great! But only if your engineer is absolutely certain that you don't need it.

I have a concrete slab ceiling reposing on the brick walls.

Excellent! With massive brick and concrete surfaces all around the room, you should be able to get very good isolation.

This is pretty surprising as there is no place to make another floor under the roof... I take it ! All I have to do is to remove the existing gypsum board 5cm below.

You will probably still need an inner-leaf ceiling. after you take out that existing drywall ceiling. That's the only way to get good isolation, even if you do have a concrete slab up there. And the new one needs to be suspended resiliently...

- Stuart -

Check with your structural engineer about that. If you need that extra space, and you can get it safely, then great! But only if your engineer is absolutely certain that you don't need it.

Yep, that's the structural specialist who told me that

You will probably still need an inner-leaf ceiling. after you take out that existing drywall ceiling. That's the only way to get good isolation, even if you do have a concrete slab up there. And the new one needs to be suspended resiliently...

Yes my future inner-leaf ceiling will only repose on the inner-leaf wooden studed walls !

Sorry to ask, but what do you think about what I posted previously july the 5th ?

Sorry to ask, but what do you think about what I posted previously july the 5th ?

Ooops! looks like I missed that one...

If I understood correctly, my leaf (OSB + Gypsum board + phonic gypsum board) must have a total density of 60kg/m2 ? OSB 1.8cm thick is 22kg/m2 Gypsum board 1.25cm thick is 9.3kg/m2 and phonic gypsum board 1.25cm thick is 11.8kg/m2. So on my plans, if i’m not mistaking I have 22+9.3+11.8=43.1kg/m2. Conclusion, I need to add an extra 4th layer to get those 17kg/m2, right ?

... Or you could put a layer of Green Glue in there some place. It doesn't add much mass, but it does put something else into the equation: constrained layer damping. You could also substitute some layers: fiber-cement board is much higher density than drywall (gypsum board): 15mm sheet is about 23 kg/m2. Two layers of that plus one of 19mm OSB would get you there. Or one OSB plus one 18mm FC plus one 16mm drywall... Lots of ways to skin a cat, as the saying goes!

But I think you are bit optimistic about your OSB density: 1.8cm of OSB only weighs about 11 kg/m2, not the 22 kg/m2 you mentioned... Nominal density is about 620 kg/m3, less than drywall, which is about 680, and less than MDF, which is about 750. So you are slightly underestimating the density of your drywall... 16mm drywall (5/8") is about 12 kg/m2, and 13mm (1/2") drywall is about 9.8 kg/m2.

i'm not sure what "phonic gypsum board" is... Do you ave a link to that?

I’ll be searching for a good not shrinking caulk ! Do you recommend some specific brands that would be sold by chance in France ?

I've had good success with Sika brand caulk. I think that should be available in France?

Those doors are awsome ! Nevertheless, it would be easier because I don’t need a window in it, but I don’t know if I’m able to do such a job, with the accuracy required, especialy without building instructions…

It's not that hard to do!

Getting a Rw of 30dB for each door would be enough you think ?

Nope, because 30 + 30 is not 60! Not with decibels. You can't add decibels of isolation from simple mass law calculations for individual doors. Mass law is not valid for multi-leaf partitions where there is air trapped in between. You have to take into account the interaction between all the parts: that's an MSM system, and it does not behave the same as two doors separately...

One of those doors need to be locked, I suppose I’ll need to drill some holes in it, or maybe it’s avoidable ?

It would be better to avoid drilling holes. Use some type of lock that does not require a hole through the door, if possible.

For now, I’m investigating on a ventilation (Incoming + outgoing) + deshumidifier. But I don’t know if the room will not warm up too fast…

HVAC is a biiiiig subject. Very big. You do need to spend some time working through that, to come up with the correct flow rates, flow velocities, sensible heat load, latent heat load, static pressure, etc. . . . .

- Stuart -

Soundman2020 wrote:Ooops! looks like I missed that one...

No problem Stuart ! Furthermore I took some time to give news about this because of some unexpected water leak from the tiled roof... It's really in bad condition and I have to renovate it before. The renovation starts next week if everything goes well ! We will take advantage of it to tear down this damn chimney.
This little "issue" took me some time and money, but this project is still on track from the end of this roof renovation

Soundman2020 wrote:... Or you could put a layer of Green Glue in there some place. It doesn't add much mass, but it does put something else into the equation: constrained layer damping. You could also substitute some layers: fiber-cement board is much higher density than drywall (gypsum board): 15mm sheet is about 23 kg/m2. Two layers of that plus one of 19mm OSB would get you there. Or one OSB plus one 18mm FC plus one 16mm drywall... Lots of ways to skin a cat, as the saying goes!

But I think you are bit optimistic about your OSB density: 1.8cm of OSB only weighs about 11 kg/m2, not the 22 kg/m2 you mentioned... Nominal density is about 620 kg/m3, less than drywall, which is about 680, and less than MDF, which is about 750. So you are slightly underestimating the density of your drywall... 16mm drywall (5/8") is about 12 kg/m2, and 13mm (1/2") drywall is about 9.8 kg/m2.

i'm not sure what "phonic gypsum board" is... Do you ave a link to that?

I'm wondering about using Green Glue... I saw in another post on the forum you said it's the same as adding a layer of gypsum board. What about the low frequencies ? In France, 1/2" drywall is about 4€/m², it makes a board cost 12€ when two tubes of GG are 16€ each (so 32€ for that board, 2.7 times more expensive). Do you think it woth it anyway, or I should only add a layer of drywall instead ?

You agree those 60kg/m² are for the inner leaf only ? If so, I'll have to put 5 layers of drywall (OSB 18mm cost 17€/m² is out, and I couldn't find this fiber-cement you suggested for anything else than wavy roof...). It sounds pretty huge, especially for the inner leaf ceiling framing. What do you think ?

Phonic gypsum board is 12.5mm thick and weight 11,8kg/m2 (http://www.castorama.fr/media_aux/538476_a1.pdf)

Soundman2020 wrote:I've had good success with Sika brand caulk. I think that should be available in France?

Yes we have some of their products, Is this one working well ? http://www.leroymerlin.fr/v3/p/produits ... ika&xtcr=2

Soundman2020 wrote:It's not that hard to do!

Alright, I'm going to do it that way !

What would be the ideal thickness of those doors in my case ? (To achieve 60kg/m² like the walls I guess )

How would you handle/reinforce/arrange the inner leaf framing to fit the door jambs and such heavy weight without deformation in time ?


I saw some schema here (http://www.johnlsayers.com/phpBB2/viewtopic.php?p=20003) and I was wondering if those backer roded and caulked gaps are needed for a full decoupled inner leaf (walls and ceiling reposing on them). If I didn't saw them, I would have caulk thin to the edge of each layer of drywall walls/ceiling, touching each other and the floor. (Don't know if what I just said is understandable )

Once again, thanks A LOT !!

Hello !

Little bump, with some photos of the new roof
This is a 40mm stiff foam insulated steel roof.
As you can see, no more chimney. But I'll still have to take off the inside colomn hidden behind the drywalled angle (you can see it in my 2nd post), and concrete the vent.

Next step, take off the aerated concret !

In addition to my previous post questions, I have some concerns about silencers, I always saw designs with only one layer of OSB/Plywood, this makes the ventilation hole through the inner leaf protected by only this one layer . I was thinking silencers have to be as thick as the wall, don't they ?

Thanks again !

Little bump for my previous posts and some news.

So I removed all the aerated concrete/drywalls. The final dimensions of the room (outer leaf) are 3.50*3.30*2.28

Here are some updated sketchs showing the actual room :
As you may see, there are some water lift from the ground (couldn’t find the english word) inside the two brick walls (and the concrete blocks wall below), because of the way they did wall construction 100 years ago. So I found and bought 40L of specific injection product to stop those water lift. I don’t want moisture between my inner and outer leafs...

Would you take off the dirt/earthy layer hooked on the brick walls ? Someone told me that’s how we insulated brick wall long ago in my region but I don’t know if it’ll help me in any way.

This wall is not really sealed, there are some gaps and lack of cement at some places. Furthermore, it’s made of 15cm hollow concrete blocks. I think I have 2 possibilities with this wall :
- beef it up with some kind of mortar/cement to seal it tight
- make another wall of plain concrete blocks (5 or 10cm thick) right against this one if the hollow concrete isn’t enough

What do you think ?

As you can see, there is a gas pipe along it ( gas inflow of the house), it was hidden behind the aerated concrete , I called a specialist to quote the cost of moving it out of the room, it’s planned for saturday.

This wall is made of concrete panels in bad condition. The concrete slab of the ceiling comes against them, not on them. They doesn’t bear anything except the pillar according to what a structural engineer said to me. So I’ll remove them, keep the pillar and build a wall in place with 10cm plain concrete blocks. Half of this wall will be built against another concrete block wall that’s just behind the concrete panel (see the sketch). Thanks to the blocks thickness the wall will come under the ceiling slab and bear it, which seems to be preferable to me.


Regarding the inner leaf
What do you think about size of the inner leaf ? If I follow what you suggested me I would have something like this : 2.90*2.70*1.98 (25cm air space + 5cm drywall so -30cm from each wall). Do you think there is something to do to get a better room ratio, reduce/increase the air gap of walls or even inner room (something worthy without losing isolation performance) ?
I was wondering if it’s really bad if I make an air gap of only 18cm (instead of 25) between the two ceilings to keep 2.05m height inside the room ?

Next steps :

- Do a sketch of the outer AND inner leaf thanks to your advices.
- Take off the bricks of the chimney corner.
- Redo the concrete slab of the door threshold I want to brick up. (there was a thin slab over 2 lines of bricks there, so I removed anything to make a proper thick steel fortified concrete bearing slab instead)
- Brick up the old door and window.
- Redo the brick seals and inject the waterproofing product into the walls.
- Bulid the wall in place of the concrete panels. It will bear the outer leaf door.
- Seal tight the ceiling slab on the walls with cement/mortar and fill the chimney hole in it.

Thanks !

I'm wondering about using Green Glue... I saw in another post on the forum you said it's the same as adding a layer of gypsum board. What about the low frequencies ?

Green Glue is excellent for low frequencies. That's where it works best, actually.

In France, 1/2" drywall is about 4€/m², it makes a board cost 12€ when two tubes of GG are 16€ each (so 32€ for that board, 2.7 times more expensive). Do you think it woth it anyway, or I should only add a layer of drywall instead ?

Green Glue is about equivalent to a layer of 16mm (5/8") drywall, not 1/2" (6mm).... I would go with the Green Glue.

You agree those 60kg/m² are for the inner leaf only ? If so, I'll have to put 5 layers of drywall (OSB 18mm cost 17€/m² is out, and I couldn't find this fiber-cement you suggested for anything else than wavy roof...). It sounds pretty huge, especially for the inner leaf ceiling framing. What do you think ?

If you really do want very high levels of isolation, then yes you will need to get around 60 kg/m2. I did warn you that it would be very expensive, but you did say that you weren't scared about that! You could get that by building a brick wall, instead of a wood-framed wall. MDF is also a bit more dense than drywall.

I couldn't find this fiber-cement

Try here...

http://www.jameshardie.fr/

http://www.cembrit.com/

http://www.archiexpo.com/architecture-d ... -7344.html

https://www.google.cl/search?q=fiber+ce ... 60&bih=700

What would be the ideal thickness of those doors in my case ? (To achieve 60kg/m² like the walls I guess

You will need to put lead sheeting inside your doors to build up the mass. If you try to do it only with wood, it will be too thick. 4mm lead weighs about 40 kg/m2, plus a thick layer of wood for the actual door, plus an extra layer of wood to "sandwich" the lead. That will be expensive, of course, but you did say that you are not scared of that!

How would you handle/reinforce/arrange the inner leaf framing to fit the door jambs and such heavy weight without deformation in time?

I would make the wall framing 2x6, not 2x4, and I would use triple studs all around the door, then use five levels of bracing on each side of that, spaced 30cm OC, with double anchor bolts across the width of the sole plate on each side, and metal brackets plus metal gussets. You will also need six very heavy duty hinges, and an extra-heavy duty door closer. Each door is going to weigh around 120 kg, so you need to provide massive support for it, and you'll need lots of help just to get it in place, plumbed and squared.

I saw some schema here (http://www.johnlsayers.com/phpBB2/viewtopic.php?p=20003) and I was wondering if those backer roded and caulked gaps are needed for a full decoupled inner leaf

Yes it is needed. You do that one layer at a time: First you put on layer #1 for the wall, then layer #1 for the ceiling, then backer rod and caulk. Then you put layer #2 on the wall, layer #2 on the ceiling, rod, caulk. Etc. When you put the drywall on the walls, first run caulk along the joint between the sole plate and the floor slab, then put down some 5mm shims to support the drywall sheet, then nail the drywall in place (resting on the shims) Then remove the shims after that layer of drywall is in place, insert backer rod, caulk. Then repeat the same procedure for each additional layer. Also caulk the joints between adjacent sheets of drywall, then mud-and-tape. And stagger the joints between layers.

In addition to my previous post questions, I have some concerns about silencers, I always saw designs with only one layer of OSB/Plywood, this makes the ventilation hole through the inner leaf protected by only this one layer . I was thinking silencers have to be as thick as the wall, don't they ?

Yes. For high levels of isolation, I use two layers of 3/4" (19mm) MDF or OSB with Green Glue in between, and I line the entire silencer box with 1" duct liner on the inside. In your case, you might want to go for three layers, since you are aiming for very, very high levels of isolation. You also need one box on each leaf, for each duct. In other words, four boxes for each room.

This wall is not really sealed, there are some gaps and lack of cement at some places. Furthermore, it’s made of 15cm hollow concrete blocks. I think I have 2 possibilities with this wall :
- beef it up with some kind of mortar/cement to seal it tight

That would work fine. A thick layer of cement-based plaster would work, then seal it with a good quality masonry sealant (paint).

However, it looks like that wall has a damp problem. The concrete blocks in the bottom two rows seem to be wet! You will need to fix that problem before you do anything more.

- Stuart -

Hey Stuart, good to see you back there, many thanks for your advices very appreciated !

Green Glue is about equivalent to a layer of 16mm (5/8") drywall, not 1/2" (6mm).... I would go with the Green Glue.

I’ve finally found some fiber-cement (but not very easy, usual material sellers here do not sell it, only thin wavy roof plates) ! It’s thinner, more dense but quite expensive and a little bit restrictive to build…
But
I found some drywall sheet 25mm (1”) thick, 24.3kg/m². 2 layers of them with green glue in between sounds great to me, very close to the 60kg/m² you recommended
http://www.pointp.fr/platre-isolation-i ... 2-A3099201
http://www.pointp.fr/platre-isolation-i ... 2-A3301892

You will need to put lead sheeting inside your doors to build up the mass. If you try to do it only with wood, it will be too thick. 4mm lead weighs about 40 kg/m2, plus a thick layer of wood for the actual door, plus an extra layer of wood to "sandwich" the lead. That will be expensive, of course, but you did say that you are not scared of that!

I have a contact who could provide me sheets of oak wood, It seems to be pretty dense, 6cm thick could be enough I think without lead if it’s 1000kg/m3 or higher. If I can’t have some of those, let’s find some lead !


To continue with the inner leaf, what do you think about it's size ? With an outer leaf of 3.50*3.30*2.28, if I follow what you suggested me I would have something like this : 2.90*2.70*1.98 (25cm air space + 5cm drywall, so -30cm from each wall/ceiling). Do you think there is something to do to get a better room ratio, reduce/increase the air gap of walls or even inner room ?
I was wondering if it’s really bad if I make an air gap of only 18cm (instead of 25) between the two ceilings to keep 2.05m height inside the room ?

Yes. For high levels of isolation, I use two layers of 3/4" (19mm) MDF or OSB with Green Glue in between, and I line the entire silencer box with 1" duct liner on the inside. In your case, you might want to go for three layers, since you are aiming for very, very high levels of isolation. You also need one box on each leaf, for each duct. In other words, four boxes for each room.

Ok so in my case, those two boxes will not fit in the air gap so it means 2 boxes inside the room screwed on the inner leaf, and 2 boxes outside the room screwed on the outer leaf.
If I did understood well, boxes will be linked by two with flexible duct inside the airgap and I have to make different diameters to slow down or speed up air flow in order to stop the sound ?

However, it looks like that wall has a damp problem. The concrete blocks in the bottom two rows seem to be wet! You will need to fix that problem before you do anything more.

For that damp problem, I puchased 40L of specific injection resin, I’ll have to drill holes every 15cm in the wall at 15cm height, put some funnels on each and pour it with this resin. I read it was very efficient with those kind of problems.

I took off the plaster boards from my future outer leaf ceiling, it’s about 9/10cm thick and reinforced with those metal beam going through. In fact, those seems to be old little train rails as they are thinner and curved on top of the slab
As you can see I tore down the chimney and figured out there is a huge gap between the brick walls and the concrete slab of the ground, about 8cm along the walls (layer of aerated concrete + layer of plaster) and much more on this corner where you see the dark soil and some old bricks in it. I’m actually feeling like I’m an archeologist.
I don’t know if I can use it to decouple the slab from the walls or if it worth it. The wall I have to build will repose on it in place of the concrete panel wall, unless I break the slab along the future wall, but I want to have your opinion before doing anything like this, I thought filling the gap with concrete, like I just did for the threshold I'm going to brick up :
Seb