Soundproofing Information & Solutions
Soundproofing a Party Wall Between Two Apartments
A comprehensive guide to reducing airborne noise through existing party walls in apartment buildings, from simple fixes to ultimate solutions.
The Problem
Reduce airborne noise coming through an existing party wall in an apartment building. Sound can travel easily through shared walls, impacting comfort and privacy.
Sound waves passing through a shared party wall between apartments
Possible Solutions
Three levels of soundproofing, choose the right one based on your noise levels and budget.
Scenario 1
Simple Solution
Add a layer of Mass Loaded Vinyl to the existing wall. Then add a layer of acoustic plasterboard over the top & paint. For high level noise, use heavier MLV or multiple layers of MLV & Plasterboard.
Align the walls with mass loaded vinyl
Follow it with a layer of acoustic plasterboard
Detailed Breakdown
> This setup adds some mass to the existing wall, which helps with soundproofing.
> However, there is no decoupling, meaning sound can still transmit through the solid wall structure.
> MLV and acoustic plasterboard will help reduce mid to high-frequency sounds, but low-frequency sounds (like bass) will still transmit to a significant degree.
Expected Rating
45–50 STC
Effectiveness
Least effective — no decoupling or air gap. Suitable for reducing TV / talking sounds.
Scenario 2
Next Level Solution
Add a layer of MLV to the existing wall. Then batten out the existing wall preferably with metal battens. Add lightweight absorbent acoustic material (11kg/m³ min) between the battens. Then add a layer of MLV across the battens. Then add a layer of acoustic plasterboard.
Align the walls with mass loaded vinyl
Add a metal framework with acoustic glass wool between studs
Add another layer of MLV and finally, cover it with acoustic plasterboard.
Detailed Breakdown
> MLV adds mass. Metal framework with acoustic glass wool creates sound absorption.
> Since studs are directly attached to the wall, there is no full decoupling.
> Another layer of MLV and acoustic plasterboard further increases mass.
> Direct connection between studs and existing wall allows some sound transmission, especially low frequencies.
Expected Rating
55–60 STC
Effectiveness
More effective than Scenario 1, with added absorption and mass, but lacks complete decoupling. Suitable for louder airborne sounds.
Scenario 3
Ultimate Solution
Line the existing party wall with MLV. Build a metal framework 50mm apart from the existing wall and not touching. Install medium density (11kg/m³ min) acoustic glasswool into the 50mm gap. Add MLV to the back of the studs. Then add acoustic batts between the studs of the new wall, followed by another layer of MLV and acoustic plasterboard.
Build decoupled metal framework with acoustic glass wool
Complete layered system: MLV, insulation, plasterboard
Detailed Breakdown
> Combines decoupling, mass, and absorption for maximum performance.
> 50mm gap with acoustic glass wool decouples the two walls — crucial for breaking the direct path of sound transmission.
> Multiple layers of MLV and acoustic plasterboard increase mass significantly.
> Acoustic batts inside the new wall enhance absorption across all frequencies.
Expected Rating
65–70 STC
Effectiveness
Most effective scenario — maximises decoupling, absorption, and mass. Excellent for low-frequency sounds like bass, music, doors closing, chairs scraping.
Reference
The Rw/STC ratings above are estimates and have not been modelled. For reference, a normal 90mm stud wall with 10mm plasterboard either side and Rw 32.
Scenario Comparison
Quick comparison to help you choose the right solution.
Scenario 1
Basic
45–50 STC
Basic soundproofing but least effective due to absence of decoupling and air gaps.
MLV layer
Acoustic plasterboard
No decoupling
Best For
Suitable to reduce TV / talking sounds
Scenario 2
Intermediate
55–60 STC
Good soundproofing level, but lacks the full decoupling of Scenario 3.
MLV layer
Metal battens
Acoustic batts
Additional MLV + plasterboard
Best For
Suitable for louder airborne sounds like TV for hard-of-hearing listeners
Scenario 3
Ultimate
65–70 STC
Highest level of soundproofing with decoupling, absorbent materials, and multiple mass layers.
Full decoupling
50mm air gap
Acoustic plasterboard
Multiple MLV layers
Acoustic batts + glasswool
Acoustic plasterboard
Best For
Suitable for louder music, heavy bass, or impact sounds
Flanking
With all 3 solutions there is the possibility of flanking, especially if dealing with impact sounds or very heavy bass sound. Below are key areas of concern.
Floor Structure
Impact sound may be travelling through the floor structure and radiating into the opposite apartment.
Ceiling Voids
Even though the party wall has been soundproofed, the two apartments will share a party wall in the void above the ceiling. Sound can still travel through and radiate into the opposite apartment.
Ductwork & Bulkheads
Do the apartments share any cavities with duct or pipework running through them? If so, sound can find its way through here.
Our Products
Soundproofing Products Australia sells a wide range of thermal and acoustic insulation products.
Mass Loaded Vinyl
High-density vinyl barrier for maximum mass addition
Polyester Insulation
Eco-friendly, non-irritant acoustic insulation
Fibertex Rockwool
Dense mineral wool for superior sound absorption
Knauf Earthwool
Sustainable glass mineral wool insulation
Fletcher Pink Batts
Premium glasswool insulation for thermal & acoustic use
Bradford Acoustic Batts
Purpose-built batts for noise reduction
We also sell Nuwrap Pipe Lagging Insulation and more. Get a free quote →
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