Soundproofing and technical rooms
Sound gets through the smallest gap.
A poorly sealed electrical box, a screw that reaches the stud, a duct without a baffle: one detail is enough for a soundproofed wall to stop working. Soundproofing happens behind the drywall. That is where we work.
A soundproofed wall, layer by layer
7 layers · 7 hold pointsWhat we close in
behind the drywall.
Every layer has a job: mass, spring, damping, airtightness. And each one has its hold point before the next.
Hold point
How a wall stops sound
Horizontal section- 1Two layers of 16 mm (5/8 in.) drywall
- 2Damping compound between the layers
- 322 mm (7/8 in.) furring channel
- 4Decoupling clip
- 52×4 stud (38 × 89 mm) at 406 mm (16 in.) o.c.
- 6Acoustic insulation, not compressed
- 7Two layers of drywall, neighbour's side
Mass
Two layers of drywall instead of one. Doubling the mass of a wall gains about 5 to 6 dB.
Decoupling
The two sides of the wall never touch. The drywall is screwed to furring channels mounted on resilient clips: vibration no longer travels through the framing.
Damping
A viscoelastic compound between the two layers turns vibration into heat, especially in the low frequencies.
Airtightness
An opening of 1% of the surface can cost half the performance. Every joint, every electrical box and every duct is sealed.
| 2×4 studs, one layer of drywall on each side | STC 33 to 35 |
| The same wall, with insulation | STC 36 to 39 |
| Decoupling clips, furring channels, insulation, double drywall and compound | STC 55 to 60 |
| Double stud wall, insulation, double drywall and compound on both sides | STC 60 to 65 |
Laboratory values, for reference only. On site, the result depends on sound travelling through floors, ceilings and ducts, and on the quality of the work. The STC rating stops at 125 Hz: for a listening room with subwoofers, we aim higher than the rating.
What we soundproof
- 01
Listening rooms and home theatres
A room within a room: decoupled walls, a ceiling hung on clips, an acoustic door, ventilation through baffles.
- 02
Walls and floors between units
Duplex, triplex, condo: voices on one side, footsteps above. The code sets a minimum between units; we can aim higher.
- 03
Studios and home offices
To record, or simply to work without hearing the rest of the house.
- 04
Mechanical and technical rooms
Furnace, heat pump, server room: we contain the noise at the source.
- 05
Meeting rooms and offices
Commercial work: partitions built up to the slab, treated plenums, conversations that stay in the room.
The soundproofing hold points.
Every point is checked and photographed before the last board goes up. The photos go into your portal.
- 01No drywall screw touches a stud: a single one is enough to short-circuit the decoupling.
- 02The drywall touches neither the floor, the ceiling nor the adjacent walls: a 6 mm (1/4 in.) gap, sealed with acoustic sealant.
- 03Electrical boxes are never back to back, and each one is covered with a putty pad.
- 04Every pipe and duct that passes through is sealed and isolated from the framing.
- 05The door: solid core, perimeter weatherstripping and an automatic drop seal, or a certified acoustic door.
Their drawings, built to the letter.
When the stakes are high, an acoustician designs the assembly and measures the result. We build to their drawings as issued, we record every gap between the drawing and the site, and we have them rule on it before we act.
Right now, we are building a hi-fi listening room this way: a room within a room, decoupled walls and a ceiling hung on clips, with a target of STC 55.
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