How to Soundproof Apartment Walls: Complete Guide to Noise Reduction Between Flats

Why Soundproofing Apartment Walls Is Essential

Noise transfer between apartments is one of the most common complaints in multi-occupancy buildings. Whether it's music from next door, television noise, conversations, or footsteps from above, unwanted sound can significantly impact quality of life and tenant satisfaction.

Effective wall soundproofing is critical for:

• Meeting Building Regulations Part E requirements for sound insulation between dwellings
• Reducing tenant complaints and improving retention rates
• Increasing property value and rental appeal
• Creating peaceful, private living environments
• Avoiding legal disputes and enforcement action

Understanding Sound Transmission in Apartment Buildings

Airborne Sound

Airborne sound travels through the air and includes voices, music, television, and general household noise. It passes through walls via:

• Direct transmission through the wall structure itself
• Gaps and penetrations (sockets, pipes, ventilation)
• Flanking paths around the edges of walls
• Lightweight construction with insufficient mass

Impact Sound

Impact sound is generated by physical contact with building elements—footsteps on floors above, doors slamming, furniture moving, or objects dropped. While primarily a floor issue, impact vibrations can travel through the structure and radiate from walls.

Flanking Transmission

Sound doesn't only travel directly through walls—it can take indirect routes through floors, ceilings, and connecting structures. Effective soundproofing must address both direct and flanking transmission paths.

Building Regulations Part E: Legal Requirements

In England and Wales, Building Regulations Approved Document E sets minimum acoustic performance standards for separating walls and floors between dwellings:

• Airborne sound insulation: Minimum DnT,w + Ctr ≥ 45 dB for walls between habitable rooms
• Impact sound insulation: Maximum L'nT,w ≤ 62 dB for separating floors
• Pre-completion testing: Required for new builds and conversions to demonstrate compliance

Failure to meet Part E can result in enforcement action, costly remedial work, and legal liability. Professional acoustic design and quality materials are essential for compliance.

Professional Soundproofing Solutions for Apartment Walls

Independent Stud Wall Systems

The most effective approach for soundproofing party walls is to build an independent stud wall that doesn't touch the existing structure:

• Construct a new timber or metal stud frame 25-50mm away from the existing wall
• Fill the cavity with 100mm high-density acoustic mineral wool (60kg/m³ minimum)
• Apply 2.6mm self-adhesive acoustic membrane (5kg/m²) to the studs for added mass
• Finish with 30mm acoustic SilentBoard or two layers of acoustic plasterboard
• Seal all perimeters with acoustic sealant to prevent flanking

This decoupled approach prevents vibration transfer and can achieve 55-65 dB sound reduction or more.

Direct-to-Wall Systems

Where space is limited, direct-to-wall systems offer good performance with minimal thickness:

• Apply SilentCloud ProMass 50 acoustic membrane directly to the existing wall
• Install timber battens to create a shallow cavity (25-50mm)
• Fill with 50mm acoustic mineral wool slabs (60kg/m³)
• Finish with 27mm acoustic SilentBoard for high-performance soundproofing
• Seal all edges and penetrations with acoustic caulk

This approach typically adds only 80-100mm to wall thickness while delivering significant noise reduction.

Resilient Bar Systems

For enhanced decoupling, use resilient channel bars:

• Fix enhanced channel bars horizontally to the existing wall at 400-600mm centres
• Install 75mm acoustic mineral wool between the bars
• Apply 4mm self-adhesive acoustic barrier membrane (7kg/m²) over the bars
• Screw two layers of 12.5mm acoustic plasterboard to the resilient bars
• Stagger board joints and seal all perimeters

The resilient bars isolate the new wall surface from the structure, preventing vibration transfer and improving low-frequency performance.

Key Materials for Apartment Wall Soundproofing

Acoustic Mineral Wool

High-density mineral wool is essential for absorbing sound energy within wall cavities. Specify:

• 100mm acoustic mineral wool slabs for maximum absorption in thick walls
• 75mm mineral wool for standard stud wall cavities
• 50mm mineral wool for space-constrained direct-to-wall systems
• Minimum density 60kg/m³ for acoustic applications
• A1 non-combustible rating for fire safety

Acoustic Membranes and Barriers

Mass-loaded membranes add blocking mass without consuming space:

• SilentCloud ProMass 50 self-adhesive membrane (5kg/m², 2.6mm) for easy installation
• Professional 4mm acoustic barrier (7kg/m²) for maximum mass in minimal thickness
• Non-adhesive ProMass 50 for mechanical fixing applications
• Flexible installation on studs, battens, or existing walls

Acoustic Boards

High-mass acoustic boards provide the final layer of sound blocking:

• 30mm acoustic SilentBoard for stud walls – engineered for maximum density
• 27mm acoustic SilentBoard – high performance in reduced thickness
• 30mm SilentBoard for solid walls – direct-fix applications
• Superior to standard plasterboard for acoustic performance

Step-by-Step: Soundproofing an Apartment Party Wall

Step 1: Assessment and Planning

• Identify the primary noise sources and frequencies
• Measure available space for soundproofing treatment
• Check for existing gaps, penetrations, and flanking paths
• Determine Part E compliance requirements
• Consider acoustic testing to establish baseline performance

Step 2: Preparation

• Remove skirting boards, electrical fittings, and fixtures from the wall
• Seal any cracks, gaps, or penetrations in the existing wall
• Install acoustic putty pads around electrical boxes
• Ensure the wall surface is clean and dry

Step 3: Frame Construction (Independent Stud Method)

• Build a new stud frame 25-50mm away from the existing wall
• Use resilient pads under sole plates to prevent vibration transfer
• Ensure no contact between the new frame and existing wall
• Maintain a clear air gap between old and new structures

Step 4: Cavity Insulation

• Fill the entire cavity with premium acoustic mineral wool insulation
• Cut slabs to fit tightly between studs with no gaps
• Ensure full coverage from floor to ceiling
• Do not compress the mineral wool—maintain loft for absorption

Step 5: Acoustic Membrane Application

• Apply self-adhesive acoustic membrane to the stud faces
• Overlap joints by 50mm minimum and seal with acoustic tape
• Ensure continuous coverage with no gaps or tears
• Press firmly to achieve good adhesion

Step 6: Board Installation

• Fix 30mm acoustic SilentBoard to the studs
• Stagger vertical joints if using multiple layers
• Leave a 5mm gap at floor and ceiling perimeters
• Use appropriate fixings at correct centres (typically 300mm)

Step 7: Sealing and Finishing

• Fill all perimeter gaps with acoustic sealant (not standard decorator's caulk)
• Seal around electrical boxes, switches, and penetrations
• Apply jointing compound and tape to board joints
• Finish with skim plaster, paint, or wallpaper as desired
• Reinstall skirting boards with acoustic sealant behind

Common Mistakes to Avoid

• Rigid connections: Any contact between new and old structures creates a sound bridge
• Gaps in insulation: Even small gaps significantly reduce acoustic performance
• Unsealed perimeters: Sound will find the path of least resistance around edges
• Insufficient mass: Lightweight materials cannot block low-frequency noise effectively
• Single-layer approach: Effective soundproofing requires mass, absorption, and decoupling
• Ignoring flanking paths: Sound travelling through floors and ceilings can bypass wall treatments

Soundproofing Existing Apartment Walls: Retrofit Solutions

If you're soundproofing an occupied apartment with minimal disruption:

• Use direct-to-wall systems with acoustic membrane and slim battens
• Apply 30mm SilentBoard for solid walls directly over existing plaster
• Focus treatment on the noisiest walls rather than all walls
• Combine with acoustic curtains, rugs, and soft furnishings for additional absorption
• Address gaps around doors, windows, and services

Cost Considerations and ROI

Professional wall soundproofing typically costs £80-150 per m² depending on specification and complexity. While this represents a significant investment, the benefits include:

• Increased property value (quiet apartments command premium rents and sale prices)
• Reduced tenant turnover and void periods
• Avoidance of legal costs and enforcement action
• Enhanced reputation and tenant satisfaction
• Compliance with building regulations and planning conditions

When to Engage an Acoustic Consultant

Consider professional acoustic design for:

• New build apartment developments requiring Part E compliance testing
• Conversions of commercial buildings to residential use
• Properties with existing noise complaints or enforcement notices
• Complex buildings with multiple flanking paths
• High-specification developments targeting premium markets

Acoustic consultants can predict performance, specify appropriate systems, and conduct pre- and post-completion testing to verify compliance.

Conclusion: Creating Peaceful Apartment Living

Soundproofing apartment walls is essential for regulatory compliance, tenant satisfaction, and property value. By combining high-density acoustic mineral wool, mass-loaded acoustic membranes, and engineered acoustic boards in properly decoupled systems, you can achieve significant noise reduction and create genuinely peaceful living environments.

Whether you're developing new apartments, converting existing buildings, or retrofitting soundproofing to solve noise complaints, the key is to use professional-grade materials, follow proven acoustic principles, and ensure meticulous installation with no gaps, bridges, or shortcuts.

For technical specifications, performance data, and installation guidance, consult with acoustic specialists who can provide Part E-compliant solutions tailored to your specific building and requirements.