Soundproofing reduces sound transmission through walls — useful for home theatres, bedrooms adjacent to noisy spaces, basement apartments, and home offices. Real soundproofing isn't 'fluffy insulation' — it's a system of mass, damping, and decoupling. The Sound Transmission Class (STC) rating measures effectiveness: standard walls are STC 30-35; soundproofed walls reach STC 50-60.

This guide covers retrofit soundproofing of existing walls. New construction allows for more aggressive systems (double-stud walls, room-within-room) covered separately.

Before you start

Three things to settle:

1. Multiple techniques layered. Real soundproofing combines: mass-loaded vinyl (MLV) layer for mass, sound-dampening drywall (Quietrock) for damping, mineral wool insulation for absorption, resilient channels for decoupling. Single-technique 'soundproofing' (just adding insulation) provides minimal improvement.

2. Address all sound paths. Sound travels through: walls (most direct), ceiling, floor, doors, electrical outlets (penetrations), HVAC ducts. Soundproofing one wall while ignoring outlets and door is mostly ineffective. Plan comprehensively.

3. STC ratings matter. Standard wall: STC 30-35 (normal speech audible through). Acoustic wall (one upgrade): STC 40-45 (loud speech audible). Premium soundproof: STC 55-60 (only loud sounds audible). Decide target based on use.

What you'll need

Tools

Drywall saw (for removing existing drywall)
Cordless drill
Utility knife
Tape measure
Stapler (for MLV)

Materials

Mineral wool insulation (Roxul Safe'n'Sound) — sound-absorbing batts
Mass-loaded vinyl (MLV) — adds mass to wall
Resilient channels (RC-1 or RC-2) — decouple drywall from studs
Sound-dampening drywall (Quietrock 510 or 525)
Acoustic caulk (for sealing penetrations)
Putty pads (for electrical box dampening)

Soundproofing is layered, not single-product

Marketing for 'soundproof drywall' or 'soundproof insulation' alone overstates effectiveness. Real soundproofing combines multiple techniques.

Mass + damping + decoupling + absorption + sealing penetrations. Skip any layer and the system fails.

Step-by-step instructions

Remove existing drywall

Soundproofing requires opening the wall to access stud cavities.

Cut drywall and remove. Save light fixtures, outlet covers for re-install.

Install sound-absorbing insulation

Stuff stud cavities with mineral wool batts (Roxul Safe'n'Sound). Mineral wool absorbs sound much better than fibreglass.

Friction-fit between studs. Don't compress — compressed insulation loses absorption properties.

Apply mass-loaded vinyl (MLV)

MLV is heavy vinyl sheet that adds mass to the wall. Roll out and staple to studs.

Overlap seams 6-12 inches; tape seams.

Adds STC 5-10 typical.

Install resilient channels (decoupling)

Resilient channels (RC-1 or RC-2) are thin metal channels that screw to studs at right angles to the studs.

The channels' design isolates drywall from studs — sound can't transfer through direct stud-drywall contact.

Screw RC channels horizontally at 16-24 inch spacing across studs.

Install sound-dampening drywall

Quietrock 510 or 525 has internal damping layer that absorbs sound vibration.

Screw to RC channels (NOT to studs through the channels — that defeats the decoupling).

Use specialty acoustic screws designed for the dampened drywall.

Seal all penetrations with acoustic caulk

Outlet boxes, switches, light fixtures: surround with acoustic caulk before drywall.

Where drywall meets floor, ceiling, and other walls: seal with acoustic caulk. Sound finds any gap.

Special putty pads inside electrical boxes prevent sound transmission through outlets.

Tape and finish

Tape and mud seams normally. Three coats with sanding between.

Verify all seams are sealed.

Address door and other paths

Solid-core door (heavier than hollow-core) with weather seals around frame.

Acoustic door bottoms (drop-down seals) when door closes.

HVAC ducts may need silencers for true soundproofing.

Common mistakes that cost you

Single-product 'soundproofing'. One product alone provides minimal improvement. Soundproofing is layered.
Skipping resilient channels. Sound transmits through direct stud-drywall contact. Decoupling is essential for STC 50+.
Not sealing penetrations. Outlets and seams leak sound. Acoustic caulk all penetrations.
Hollow-core door with soundproof walls. Door becomes the weakest link. Solid-core door + seals required.
Wrong insulation type. Fibreglass absorbs less than mineral wool. Use Roxul Safe'n'Sound for soundproofing applications.

Frequently asked questions

What STC rating do I need?

STC 35: normal residential, blocks normal speech.

STC 45: bedrooms, decent privacy, blocks loud speech.

STC 55-60: home theatres, music rooms, blocks most sounds except very loud.

Match target to use.

Does adding insulation alone help?

Marginally. Adding insulation to an empty wall cavity raises STC by 2-5 points.

For meaningful soundproofing, add mass + decoupling + sealing on top of insulation.

What drives the cost of soundproofing a wall?

The biggest driver is your STC target: a basic improvement uses added insulation and a single layer of drywall, while higher ratings stack resilient channel, sound-rated board, and damping compound.

Wall size, whether existing finishes are removed, and the amount of labour and refinishing all factor in. We provide a clear itemized proposal so you understand exactly what is included.

When to call us instead

Real soundproofing requires expertise and specialty materials. We do home theatre and acoustic projects as part of larger renovations.

Book a free 60-minute site visit →

Related Ottawa services

If you're building a home theatre or acoustic space, our renovation team handles soundproofing as part of fixed-price work. Book a free 60-minute consultation.