Translate This PageHere I am, back on track for that project I started some years ago on John Sayers forum (RIP
). It took forever to get it where it is right now, for some reasons, I’ll not explain for those not related with the subject. Got some resources and advices from Stuart back in the day, right time to share it here now, move it forward, and get this done ! And if it helps some other people here, I’ll be the happiest ! 
About the project :
I’m a drummer and guitarist, and my objective is to build a rehearsal room, to work on my every day practice routine, play with some bandmates regularly and record demos. For the past years I practiced on electronic and quiet stuff, but I can’t stand it anymore.
I’m building it into an outbuilding built right against my house, where there is that room about 11m².
I live in a quiet village in the north of France where neighbors are not really far away, 10 meters from the room for the closest, with his garden right behind the outer wall. It is really important for me to not disturb anyone with my passion and what I want to be my profession. Even if my neighbor said he doesn't care and won’t be pissed off, I know how drums can be annoying when practicing, especially if he wants to relax in his garden on summer days, I can’t ask that much of them. I want to be able to play every day and/or night being sure I won’t be disturbing anyone in the long run.
So, as a drummer I’m loud about 110dB and would like to get 40-50dB max outside the room, so aim for the best isolation I can afford to achieve that goal (with 20k€)
From where I was on John Sayers forum, there are some new improvements. For those who want to start the story from the beginning here you go : http://johnlsayers.com/phpBB2/viewtopic.php?f=2&t=20508
About the room :
It’s a square room 3.35*3.38*2.36 (l*w*h in meters). That’s the outer leaf.
Walls :
Are made of 2 old plain brick walls 40cm thick, 1 plain cinder block wall 20cm thick and 1 double hollow cinder block wall, 10 + 15cm thick. There is no more window, I bricked it up, such as another doorway (that room had two).
Floor :
It’s right on the ground, on a new concrete slab I made 20cm thick, decoupled from the walls. I broke the previous one for two reasons : 1. it was too thin to carry the load of the inner leaf (3-5cm thick at some points). 2. I wanted to gain some extra ceiling height so I dug down to get that 20cm thick slab and 12cm extra height. It will stay plain concrete and not covered with anything.
Ceiling :
It’s made of the ancient concrete “slab”, 10cm thick with half a dozen old train tracks as structure, the concrete has been poured in between the tracks. I wanted to beef up that slab with a serious one, so I concreted 20cm more over it. Of course to carry that load I put 4 I shaped metal beams(RSJ ?) 10cm thick with the advice of a structural engineer.
This is where I am now for the room, the inner leaf doesn’t exist yet.
What is planned for the next steps and weeks :
The inner leaf and doors are the next steps. The carpenter I hired will start installing wood framing and the doors in 3-4 weeks if everything goes well.
Framing and air gap :
The frame will be made of wooden studs and joists (17.5cm*6.3cm called “bastaing” in french). None of them will touch the outer leaf (2.5cm away), they will only repose and be blot on the concrete slab. The air gap between the leaves will be 20cm, filled completely with soft fiberglass 30kg/m3 (2 layers of 10cm thick each). Do you know if less or more dense fiberglass could be as good as 30kg/m3, or rigid better than soft ? (wondering because of some current shortage due to the pandemic… (Rockwool is out of the table))
I don’t know for now if I need a vapor barrier or not, what do you think ?
Inner leaf :
On that frame I’ll use multiple layers of Fermacell boards (made of plaster and cellulose fibers). Those are pretty cheap and dense 1150kg/m3 . They exist in several thicknesses, 10 to 18mm, but the 13mm are more common and cheap. It will be 4 layers of 13mm for 5.2cm thick. Those boards are straight edged, so glued together with specific glue (no mud & tape). With that I’ll achieve some 60kg/m² surface density, for a cost of 8.5€/m²*4 so 34€/m².
I’ll use greenglue (viscoelastic) in the middle of the layers, so 2 boards, greenglue then 2 boards again.
The actual size of the room into the inner leaf will be 2.85*2.88*2.11 (l*w*h in meters)
Doors :
I hired this carpenter to also do and install the doors on the framing and the outer leaf. They will be made of a sandwich of massive oak and lead. Oak for high density wood, and lead to reduce the thickness. So 3 layered oak (3cm), lead board, 3 layered oak (3cm) again for about 6cm thick. There will be 2 seals (3 was not possible they said
). To close them, we will not drill any hole in there, only fixed door handle and big magnets.
Electrical stuff :
3 separated lines, 1 for the lights 16A, and 2 for outlets 20A. No holes in walls, only external boxes, of course exept for the only cable entry on each leaf, which will not be in front of each other, and caulked. The rest will be apparent through PVC tubes in the room.
Silencers and Hvac :
The 4 silencers box air in an out, 2 for the outer leaf, and 2 for the inner leaf. As they can’t stand in the air gap, they will be right against the walls. They will be made of the same materials as the inner leaf (4 Fermacell Layers + greenglue). The duct will be 80mm in the silencers and 120mm between into the air gap. Supply and return vents will be on opposite walls.
I don’t know yet the size they will be.
For now, I don’t really know how to decouple them from the leaves with getting them airtight anyway.
I’m still searching about hvac to do it the right way, but struggling a little bit, between heating, cooling and providing fresh air and avoiding moisture in such a small room.
I thought about putting a minisplit outside the building, ducted to an unit inside the room, an air exhauster on the air outtake of the room, and nothing but natural air flow on the air intake of the room. But I'm still not sure about this. I called a pro to propose a solution, but it did not inspire me confidence... I’ll call another one hoping he’ll not look at me with such big eyes about the project (don’t know if that’s correct in english tho
)...Drum Riser :
I did not really dig the subject, but I think I saw a scheme somewhere of wooden framing, OSB/MDF on top, resting on rigid wool/fiberglass.
