Coating finish on "cinder block" (drumroom)

[Bren Drums]

Hello i'm new here.
I dont know if it's the right place to post my question.
Im building a drum room in my garden.
Neighborhood at 10 meters. Calm country.
The wall are in "cinder block".(Cinder block 20 cm +15cm air (filled with rockwool)+2 layers of drywall)
For the external wall (cinder block) i will make a "coating finish".
My question is : do i have to do a coating on the interior wall ?
If I do this, will it reduce the sound outside of the room ?
Thanx in advance from France to the community.

[DanDan]

You are welcome. Do fill in your Profile a bit more. Adding a Render layer of around 12mm of cement or plaster onto a block wall should increase Transmission Loss by 3dB or so. It is important fully fill the gaps between blocks, no bubbles, gaps.

[Bren Drums]

You are welcome. Do fill in your Profile a bit more. Adding a Render layer of around 12mm of cement or plaster onto a block wall should increase Transmission Loss by 3dB or so. It is important fully fill the gaps between blocks, no bubbles, gaps.

Thanx DanDan for your answer.
I fill my profile a bit more, i'm not a regular of forums.
I read a lot of forums but not as an 'active' forum person...

I will made a layer of 12MM on external.
The block have joints, but there is on some junction a little space éMM or 3mm of space) , do you think i need to fill this "space/hole" with ciment or plaster ?
I try to put photos, but i always got a problem of (pixel, size etc...).grrr
Thanx in advance for your help.
Brendan

[DanDan]

Such holes would drive me mad! My problem is the holes inside in the joints which I cannot see!
I would probably do my best to fill anything visible and then do the 12mm (or more) cement render.

[Paulus87]

You are welcome. Do fill in your Profile a bit more. Adding a Render layer of around 12mm of cement or plaster onto a block wall should increase Transmission Loss by 3dB or so. It is important fully fill the gaps between blocks, no bubbles, gaps.

Thanx DanDan for your answer.
I fill my profile a bit more, i'm not a regular of forums.
I read a lot of forums but not as an 'active' forum person...

I will made a layer of 12MM on external.
The block have joints, but there is on some junction a little space éMM or 3mm of space) , do you think i need to fill this "space/hole" with ciment or plaster ?
I try to put photos, but i always got a problem of (pixel, size etc...).grrr
Thanx in advance for your help.
Brendan

Sometimes the small gaps are left on purpose, in order to vent the cavity between the drywall and concrete blocks. If you fill in this gap then you risk moisture being trapped inside the cavity forming condensation on the inner face of the concrete blocks. The gaps provide venting to help the moisture escape.

Exterior walls and roofs are complicated when it comes to sound isolation since they either need to be sufficiently insulated so that the dew point happens way before reaching any interior surface, or in the case of cold assemblies they need sufficient venting so that any moisture/vapour that does either get into a cavity or condenses has a chance to escape to the outside world. Obviously, holes are not ideal although if small enough they become much less of an issue IF you have an inner shell which is completely air tight.

I think before going forward we need to study exactly how your room is constructed in regards to its wall and roof assemblies otherwise you'll just be ripping it all out again if you get moisture problems in the future

[Bren Drums]

Hi everyone here is my "conception" of the drum room.

THE WALL
Ciment coating on external wall.
Hydrofuge coating on the "basement cinder block".
Cinder block.
100 mm rock wool. "hi density".
Metalic rail filled with 45mm rockwool
2 layers of drywall.

ROOF :
Roof tiles/"anti rain+air aeration"
framework
Rockwool between the framework.

"roof 1"
2 layer drywall  (suspended on the framework)

"roof 2" (fixed on the walls).
100mm of rock wool
2 layers of drywall.

Order of conception : 
-masonry : done (artisan)
-Roof tiles/ framework+antirain : done (artisan)

Then : done by me
-Roof 1
-walls isolation(rockwool+drywall).
-roof 2.

I hope it help you understand.
Thanx in advance.