How To Soundproof A Floor

Understanding the Types of Floor Noise

Before soundproofing, it’s crucial to identify the type(s) of noise you’re dealing with, as different noises require different solutions:

• Airborne Noise: This is sound that travels through the air and then through solid structures. Common examples include conversations, music, television sounds, and pets barking. These sound waves make surfaces vibrate, transmitting noise to adjacent rooms.
• Impact Noise (or Structure-Borne Noise): This occurs when an object makes direct contact with the floor, creating vibrations that travel through the building’s structure. Footsteps, dropped items, moving furniture, and children playing are typical examples of impact noise.

Often, you’ll be dealing with a combination of both airborne and impact noise.

Key Principles of Effective Soundproofing

Soundproofing relies on a few core principles. Often, the best results come from using a combination of these:

• Adding Mass: Dense, heavy materials are harder for sound waves to vibrate, thus reducing sound transmission.
• Decoupling (Isolation): Creating a separation between structural elements (like the floor surface and the joists, or the ceiling below and the joists) breaks the path for vibrations to travel.
• Sound Absorption: Using porous, fibrous materials to absorb sound energy, converting it into a small amount of heat. This is particularly effective for airborne noise within cavities.
• Damping: Applying materials that dissipate vibrational energy, often used in conjunction with mass or decoupling.
• Airtightness: Sealing gaps and cracks prevents airborne sound from leaking through.

Soundproofing Methods for Different Floor Types

Timber Joisted Floors

Timber floors are common in many homes and are often the most problematic for sound transmission, especially between flats or different storeys in a house.

Addressing Airborne Noise

• Insulating Between Joists: This is highly effective. The empty space between joists can act like a drum, amplifying sound. Filling this void with dense acoustic insulation significantly absorbs airborne sound.
• Materials: High-density Insulation Slabs are ideal. Products like Rockwool RWA45 Slab, Rockwool Insulation Slab, Rockwool Flexi Slab, or Knauf Insulation Slab (all types of Mineral Wool Insulation) are excellent choices due to their sound-absorbing properties. Acoustic Insulation Rolls can also be used, ensuring they are installed at the correct density. 
• Adding Mass to the Floor: Laying dense boards on top of the subfloor (underneath your final floor finish) can help block airborne noise. Specialist acoustic floorboards or cement particle boards are options.
• Improving the Ceiling Below: If accessible, adding mass and decoupling to the ceiling of the room below (e.g., using resilient bars and two layers of acoustic plasterboard) is also very effective.

Addressing Impact Noise

• Acoustic Underlays: Laying a high-quality acoustic underlayment directly beneath your floor finish (carpet, laminate, wood) is often the simplest first step. Materials like dense rubber, cork, or specialised foam can absorb impact energy.
• Floating Floors: This involves creating a new floor surface that is structurally isolated from the joists. This can be done using:
• Resilient battens or acoustic cradles fixed to the joists, with a new chipboard or plywood deck laid on top.
• Laying floor insulation boards (specifically high-density acoustic grade boards, not just thermal boards) directly onto the subfloor, then a new deck on top.
• Carpet with Thick Underlay: Carpet is naturally effective at reducing impact noise due to its cushioning effect. A high-quality, dense underlay will further enhance this.
• Sealing Gaps: Airborne sound will find any weakness. Use acoustic sealant around the perimeter of the room, where floorboards meet skirting boards, and around any service penetrations. 

Concrete Floors

Concrete floors are inherently better at blocking airborne noise than timber floors. However, impact noise can still pose an issue.

Addressing Impact Noise

• Acoustic Underlays: As with timber floors, laying a resilient acoustic underlay beneath hard floor finishes (laminate, wood, tiles) is crucial.
• Floating Floor Systems:
• A timber floating floor can be created on top of the concrete using battens on a resilient layer (e.g., acoustic foam or rubber).
• A floating screed can be laid on top of a layer of high-density acoustic floor insulation boards or specialised acoustic membranes.
• Soft Floor Coverings: Carpet with a substantially thick underlay remains one of the most effective ways to reduce impact noise on concrete floors.

Step-by-Step: Common Floor Soundproofing Approaches

Please Note: The methods and considerations outlined below are intended as general guidance and for informational purposes only. Effective soundproofing can be complex and is highly dependent on your specific property, the types of noise, and the quality of installation. For projects requiring compliance with UK Building Regulations (including Part E), or for tailored advice on significant noise issues, it is always recommended to consult with qualified professionals, such as an acoustic consultant or an experienced builder. Always follow the specific manufacturer’s instructions for any products used.

Soundproofing a Timber Floor from Above (DIY Friendly):

• Carefully lift existing floorboards or remove the current floor covering.
• Clean out the joist cavity.
• Install Acoustic Insulation Rolls or Insulation Slabs (e.g., Rockwool RWA45 Slab) snugly between the joists, ensuring no gaps.
• Lay a high-quality acoustic underlayment over the subfloor/joists (or consider resilient battens for better decoupling).
• Relay the original floorboards or install your new floor finish. 
• Seal the perimeter of the room and around any pipes with acoustic sealant. Use Insulation Tapes designed for acoustic applications on joints if using rigid acoustic boards.

Soundproofing a Timber Floor from Below (More Disruptive but Highly Effective):

• Protect the room below and remove the existing ceiling plasterboard. 
• Install Acoustic Insulation Rolls or Insulation Slabs between the joists from below.
• Fix resilient bars perpendicular to the joists (this decouples the new ceiling).
• Attach two layers of high-density acoustic plasterboard to the resilient bars, staggering the joints.
• Tape and seal all plasterboard joints and the perimeter with acoustic sealant.
• Skim plaster and decorate.

Important Considerations

• Building Regulations: For conversions or new builds in the UK, Part E of the Building Regulations sets out requirements for sound insulation between dwellings. Ensure your solution meets these standards if applicable.
• Floor Height: Some soundproofing solutions, particularly floating floors, will raise the floor level. Consider the impact on doors, skirting boards, and thresholds.
• Flanking Transmission: Sound can travel around a soundproofed floor via adjacent walls or other structural elements. For best results, consider addressing potential flanking paths.
• Type of Final Floor Finish: Hard floor finishes like wood, laminate, or tiles will always transmit more impact noise than carpet. If choosing a hard floor, investing in high-quality acoustic underlayment is essential.

Conclusion

Soundproofing a floor can dramatically improve your quality of life by reducing unwanted noise. By understanding the types of noise and applying the principles of adding mass, decoupling, and absorption using effective materials like dense Insulation Slabs or Acoustic Insulation Rolls between joists, and potentially acoustic Floor Insulation Boards in specific systems, you can create a quieter, more peaceful home environment. Always assess your specific noise issues and floor type to choose the most effective solution for your needs.

Disclaimer: This blog post provides general guidance. Specific soundproofing performance will depend on the exact materials used, quality of installation, and the existing structure. For projects requiring compliance with Building Regulations Part E, or for complex noise issues, it is recommended to consult with a qualified acoustic consultant.