Soundproofing Walls in Adelaide: What Actually Reduces the Noise You Hear
The short answer
Soundproofing walls in Adelaide is a build-up problem, not a product problem. Four things decide what you hear—how heavy the wall is, whether its two faces are mechanically joined, how completely it is sealed, and what the sound can travel around through instead. Add acoustic batts to a single-framed wall with a gap at the ceiling line and most of the noise keeps taking the easier route.
How sound gets through a wall
Airborne sound sets one face vibrating, the vibration crosses to the other face, and that face radiates it into the next room. Every practical measure interrupts one of those steps.
Mass
Heavier surfaces are harder to set moving. Doubling the lining on one face, or swapping a standard sheet for a denser board, adds mass without touching the framing—usually the cheapest worthwhile improvement.
Separation
Mass alone has limits, because studs bridge the two faces and carry vibration straight across. Breaking that connection—two independent frames, staggered studs, or resilient mounting between frame and lining—often does more than another layer of board. The Building Code’s definition of discontinuous construction sets the principle: at least a 20 mm cavity between two separate leaves, resilient ties where masonry leaves must connect, and no mechanical linkage elsewhere except at the periphery.
Source: ABCB, NCC Housing Provisions Part 10.7 Sound insulation.
Sealing
Air gaps are why careful walls underperform. Hebel’s party-wall literature puts it bluntly: perimeter gaps and penetrations have to be completely sealed with an appropriate fire and acoustic rated sealant for the system to reach the ratings it was tested at.
Sources: CSR Hebel party wall systems and the PowerPanel intertenancy and dual zero boundary walls design and installation guide.
Absorption inside the cavity
Acoustic batts work on the sound energy bouncing inside the cavity, not on the vibration crossing the studs. High-density glasswool sold for this purpose—CSR Bradford’s SoundScreen is the one most Adelaide builders will name—contributes to a tested system’s result, but will not by itself quieten a single-framed, hard-linked wall.
Sources: Gyprock acoustic considerations and CSR Bradford SoundScreen acoustic wall insulation.
The paths around the wall
Flanking transmission is sound arriving by any route other than straight through the wall, and in an existing house it is often the dominant one. The wall gets blamed; the ceiling, floor or ductwork is responsible. Common paths:
- A continuous roof space or ceiling cavity running over the wall
- Ducted evaporative cooling outlets linked by the same ceiling void
- Downlights, exhaust fans and vents cut through the lining on both sides
- Power points set back to back in the same stud cavity
- Continuous floor framing or hard finishes carrying impact noise
- Hollow-core doors and unsealed frames in the same wall run
ABCB guidance covers flanking and the measures used to describe wall performance: Rw for airborne sound insulation, and Ctr as a spectrum adaptation term weighting the result towards lower frequencies.
Source: ABCB, Sound Transmission and Insulation in Buildings handbook.
What the Code requires between attached dwellings
A wall inside one house is a comfort decision. A wall between two dwellings is a compliance one, and the two get confused constantly on townhouse and dual-occupancy sites.
For a separating wall between Class 1 buildings—attached houses, townhouses and terraces—the Housing Provisions require airborne sound insulation of Rw + Ctr not less than 50. Where that wall separates a bathroom, sanitary compartment, laundry or kitchen from a habitable room other than a kitchen next door, it must also be of discontinuous construction. It has to continue to the underside of the roof, or to a ceiling giving the same insulation, so the roof space cannot flank over the top.
That wall almost always carries a fire resistance requirement too, and one tested system usually satisfies both. Hebel panel systems are common here because the panel itself contributes the fire rating. Code editions change, so confirm with the certifier which one applies to your approval.
Sources: ABCB, NCC Housing Provisions Part 10.7 and Part 9.3 Fire protection of separating walls and floors.
Why Adelaide walls differ
Infill is where most of this comes up. The state’s planning strategy points denser housing at established corridors like Prospect Road, Unley Road and The Parade—more attached dwellings sharing a wall in suburbs built as detached cottages.
The existing stock behaves differently again. A solid double brick wall in Norwood or Unley has useful mass but no separation, so its weakness is the roof space above it. A 1990s timber-framed house in Golden Grove or Salisbury has the opposite problem—light linings, hard-linked studs and a ceiling void running the length of the building. Adelaide’s widespread ducted evaporative cooling adds a second shared void, which is why bedrooms either side of a well-built wall still hear each other.
External noise is a glazing and sealing question more than a wall one—worth separating out before money goes into the wrong element. Our Adelaide service area covers the suburbs where most of this work sits.
Soundproofing walls in an existing Adelaide home
Retrofitting comes down to how much of the wall you are willing to open, in rough order of disruption:
Seal what is already there
Close service penetrations, pack door frames, stagger back-to-back power points and deal with the ceiling line. Often the difference between a wall that underperforms and one that performs as designed.
Add mass to one face
A second layer of dense lining, sealed at the perimeter. Costs a little room width, and cornice, skirting, architraves and switch plates need resetting.
Open the wall and rebuild the cavity
Strip one face, insulate, add resilient mounting or a second independent frame, then reline. Specify it from a tested build-up, because you only want to do it once.
Where flanking dominates, none of that satisfies alone: the roof space, ducting and ceiling penetrations may matter more.
Anything that adds real weight to an upper floor, or removes part of a wall rather than lining it, changes how load travels through the building—a structural question before an acoustic one. Our guide on removing a load-bearing wall in Adelaide covers what to confirm first.
What to confirm before requesting a quote
The more of this you can answer, the more useful the response. Our project planning guide covers the rest.
- Whether the wall separates two dwellings or two rooms in one dwelling
- What the noise is—voices, television, footsteps, traffic, plant—and when you hear it
- The existing construction, lining thickness and whether the cavity is insulated
- What sits above the wall: a ceiling and roof space, a floor, or continuous framing
- Whether evaporative cooling, downlights or exhaust fans penetrate the ceiling both sides
- Any acoustic report, tested system number, approved drawings or certifier requirement
Where a documented system already exists, our Adelaide walling installation scope is to build it exactly as specified, so the wall on site matches the wall that was tested.
Who does what
- Acoustic consultant
- Identifies the dominant path and specifies a build-up that will achieve the target. Worth engaging before spending on a retrofit.
- Building certifier
- Confirms which Code requirements apply and accepts the evidence that the chosen system satisfies them.
- Structural engineer
- Needed where added mass, an extra frame or an altered opening changes how loads travel—particularly upstairs or on a reactive clay site.
- Wall system installer
- Builds the specified system to its documentation, including the sealing and junction details that decide whether the tested result is reached.
Common questions
- Can an existing wall be brought up to the separating-wall standard?
- Sometimes, but it has to be assessed rather than assumed. The requirement covers the complete construction including the junction at the roof, so a retrofit that cannot address the ceiling line rarely gets there.
- Who do I contact about noise from a neighbouring property?
- In South Australia it depends on the source. Councils handle neighbourhood nuisance such as construction noise, pool pumps and air conditioners; SAPOL handles domestic noise such as parties; the EPA deals with licensed commercial and industrial premises. That is a separate matter from building work on your own wall. Where the external wall is still being chosen, compare systems on Hebel versus brick veneer.
Sources and further reading
- Australian Building Codes Board
- NCC Housing Provisions, Part 10.7 Sound insulation and Part 9.3 Fire protection of separating walls and floors
- Australian Building Codes Board
- Sound Transmission and Insulation in Buildings handbook (PDF)
- Manufacturer technical guidance
- CSR Hebel: Party Walls and its intertenancy wall design and installation guide, Gyprock: Acoustic Considerations and CSR Bradford: SoundScreen acoustic wall insulation
- Environment Protection Authority South Australia
- Neighbourhood nuisance and noise
