Soundproofing an existing floor can be challenging, but it is possible with the right materials and techniques. The goal of soundproofing a floor is to reduce airborne noise (like voices, music, TV) and impact noise (like footsteps) from transmitting through to the room below. While it’s unrealistic to expect a floor to become completely soundproof, there are ways to significantly reduce the amount of noise transfer.
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Quick Answers
Here are some quick answers to common questions about soundproofing existing floors:
- What is the best material for soundproofing floors? Mass loaded vinyl (MLV) is considered one of the most effective materials for reducing airborne and impact noise transmission through floors.
- Does carpet help soundproof floors? Carpet and carpet padding can help block some impact noise from footsteps, but are not very effective at blocking airborne noise.
- Can you install soundproofing under existing flooring? In most cases, yes – soundproofing materials like MLV can be installed underflooring like carpet, hardwood, laminate, etc. The flooring would need to be removed and reinstalled.
- Is green glue good for soundproofing floors? Green glue is an effective noise blocking compound that can be used under new flooring or subfloors to reduce transmitted noise.
- Can you install a floating floor over an existing floor? Floating floors or subfloors decoupled from the existing floor framing are a very effective way to reduce noise transfer through floors.
Understanding Noise Transfer Through Floors
To understand how best to soundproof an existing floor, it helps to first understand how noise travels from one room to another:
- Airborne noise: Noise like voices, music, TV, etc transmits through the air and can pass through gaps in the floor into the room below. Insulation blocks and absorbs this airborne noise.
- Impact noise: Footsteps and dropped objects transmit vibrations directly into the floor structure that radiate noise into the room below. Isolating the floor from impacts is key.
- Flanking noise: Noise can also travel indirectly through adjoining walls and structures. Completely isolating the floor helps block flanking paths.
With an existing home, we don’t have the opportunity to build an ideal soundproof floor system from scratch. But we can take steps to address each of these noise paths as much as possible with our retrofit.
How to Soundproof an Existing Floor
Here are the key steps for soundproofing an existing floor:
1. Inspect and Prepare the Floor
- Remove existing floor coverings like carpet, vinyl, or laminate flooring.
- Inspect the underlying subfloor for damage or squeaks and repair as needed.
- Ensure subfloor is clean and level before installing new soundproofing materials.
- Seal gaps around the perimeter and between boards with acoustical sealant.
2. Add Noise Damping Compounds
- Apply sound damping glue like Green Glue between the subfloor and new layers.
- This converts noise vibrations into heat energy and blocks transmission.
- Follow manufacturer’s instructions for trowel sizes, drying time between layers, and compressing the compound.
3. Install Sound Isolation Materials
- Mass Loaded Vinyl (MLV) mats provide excellent density and vibration damping.
- Alternatively, try products like AcoustiCORK or QuietWalk for airborne and impact sound insulation.
- Overlap seams at least 4-6” and seal with acoustic caulk.
4. Build a Floating Floor
- Construct a floating subfloor by installing a second layer decoupled from the existing floor.
- Use acoustic isolation clips or resilient channel to decouple layers.
- Top with multiple layers of MDF, plywood, OSB for mass.
- Floating floors prevent impact noise transmission to fixed structures.
5. Reinstall Finished Floor
- Reinstall carpet and pad, laminate, hardwood, vinyl, or other finished flooring.
- Choose soft surfaces like carpet for best impact noise reduction.
- High quality, dense pad improves airborne and impact performance.
- Seal edges with acoustical caulk to limit flanking noise.
Soundproofing Options by Floor Type
The best soundproofing methods can vary depending on your existing floor construction:
Carpeted Floors
- Replace carpet, upgrade to thick, dense pad
- Add MLV under carpet, sealing seams
- Install secondary subfloor on acoustic isolators
- Seal gaps at wall/trim edges with acoustical caulk
Wood Floors
- Remove flooring, install MLV or other membranes
- Reinstall over acoustic mat using glue/nails
- Build floating floor over vibration isolators
- Carefully seal any gaps around boards or at edges
Concrete Floors
- Apply sound damping glue before installing new layers
- Build floating floor with isolators and multiple layers
- Top with carpet, laminate, or other finished flooring
- Pay special attention to sealing cracks, gaps, penetrations
Laminate/Vinyl Floors
- Remove flooring, install MLV sound mats underneath
- Reinstall flooring over new acoustic layer
- Alternatively, build floating floor system on isolators
- Careful workmanship is key to limit noise leaks
Impact Noise vs. Airborne Noise
Impact noise from sources like footsteps requires different soundproofing strategies than airborne noise like voices or music:
| Impact Noise | Airborne Noise |
|---|---|
| Transmitted through direct contact with floor | Transmitted through the air and gaps |
| Floating floors effective for breaking contact | Insulation blocks and absorbs airborne paths |
| Soft surfaces (carpet, felt, cork) also help | Sealing gaps limits transmission routes |
| Impact noise isolators like clips or channels | Increasing mass also helps block airborne noise |
The most effective soundproofing treatment will address both major noise types using a combination of appropriate techniques.
Sound Transmission Class (STC) Ratings
The Sound Transmission Class (STC) rating is a measure of a material or assembly’s ability to block airborne noise transmission. Higher STC values indicate better sound blocking performance:
| STC Rating | Noise Reduction |
|---|---|
| 25-30 | Marginal noise reduction |
| 30-40 | Moderate noise reduction |
| 40-50 | Good noise reduction |
| 50+ | Excellent noise reduction |
Adding multiple layers with high STC ratings will give the best soundproofing performance. Impact insulation class (IIC) is a related rating for blocking impact noise.
Costs of Soundproofing Existing Floors
Soundproofing an existing floor professionally may cost $1-$5 per square foot or more depending on materials used and floor area. DIY can reduce costs, but take more time and labor. Typical costs include:
- Mass loaded vinyl – $0.50-$1 per square foot
- Green glue noiseproofing – $0.75-$1.25 per square foot
- Cork underlayment – $0.75-$2 per square foot
- Acoustic isolation clips – $1-$4 each
- Soundproof carpet and pad – $3-$8 per square foot installed
In a 15×15 ft bedroom this could amount to $700-$2500+ in materials for a professional installation. The investment may be worthwhile though for significantly increasing quiet and privacy.
Conclusion
Soundproofing an existing floor is definitely possible with the right combination of noise blocking and isolation techniques. Key steps include adding damping compounds, sound insulation materials, building a floating floor decoupled from the structure, and proper air sealing. While a retrofit floor will not be as ideal as building new from scratch, 50% or more reduction in noise transfer is achievable with careful selection of materials and diligent installation. With the saved cost of not replacing the floor structure and the meaningful improvement in noise reduction, soundproofing an existing floor is usually a worthwhile investment.