Selecting Underlayment That Complies with Acoustic Codes

Because Footfall Isn’t Just Annoying—It’s a Code Violation

In multi-story commercial buildings, mixed-use developments, and multifamily residences, sound transmission through floors is more than a nuisance—it’s a regulatory issue. Across North America, building codes and local ordinances now require acoustic performance thresholds to minimize footfall noise, airborne sound, and vibration. And the unsung hero in achieving those targets? The underlayment.

For architects, flooring contractors, and procurement teams, selecting the right acoustic underlayment means balancing compliance, performance, and material compatibility. And for distributors, stocking underlayments that meet or exceed sound codes helps clients build quieter, code-compliant spaces that occupants actually enjoy living and working in.

What Acoustic Codes Actually Require

Most jurisdictions reference two key sound transmission metrics:

IIC (Impact Insulation Class): Measures the ability of a floor-ceiling assembly to reduce impact noise (like footsteps or dropped items).

STC (Sound Transmission Class): Measures resistance to airborne noise (like voices or music) traveling through the assembly.

Typical minimums for multifamily and commercial occupancies:

IIC ? 50 (laboratory) or ? 45 (field)

STC ? 50 (lab) or ? 45 (field)

These thresholds are often required in:

International Building Code (IBC)

LEED for Homes and WELL Building Standard

Local ordinances or condo association rules

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Types of Underlayments That Improve Acoustic Performance

1. Rubber Underlayments

Recycled or synthetic rubber sheets offer excellent IIC values and long-term durability under all flooring types.

Best for: Concrete subfloors under engineered wood, vinyl plank, or tile

Advantages: Mold-resistant, dense, compatible with radiant heat

IIC ratings: 60–70 when used under floating or glued floors

2. Cork Underlayments

Natural cork provides both thermal and acoustic insulation, with good resilience under laminate or wood.

Use in: Light commercial or multifamily spaces wanting sustainable materials

Limitations: Less durable under heavy commercial loads

3. Foam and Fiber Pads with Acoustic Ratings

High-density foam or fiber underlayments are commonly used under luxury vinyl tile (LVT), laminate, or carpet tile.

Pros: Lightweight, easy to install, often integrated with vapor barriers

IIC performance: Can reach 58–62 with proper assembly

4. Sound Control Mats for Tile Applications

For ceramic or stone floors, specially designed mats are used under mortar beds to reduce impact noise.

Compatible with: ANSI A118.12 crack isolation requirements

Required in: Hotels, bathrooms, kitchens, and high-end condos

Factors to Consider When Choosing Acoustic Underlayment

Flooring type: Underlayment must match the floor—floating, glued, or nailed

Subfloor type: Wood vs concrete dramatically affects acoustic performance

Moisture conditions: Vapor barriers may be needed on slab installs

Installation method: Taped seams, glue-down, or loose lay?

Fire rating: Look for UL-classified assemblies when required

Thickness and density: Heavier isn’t always better—acoustic efficiency depends on composition

Installation Tips to Ensure Performance

Don’t substitute underlayment mid-project—sound tests are based on full assemblies

Seal perimeter gaps to prevent flanking noise

Ensure full floor coverage, even under built-ins or closets

Coordinate with fire stopping and slab penetrations—acoustics can be compromised at MEP cutouts

Test assemblies in field when needed—especially for high-end or code-sensitive builds

Where Code-Compliant Underlayments Are Non-Negotiable

Multifamily residential units above grade

Hotels and hospitality suites or shared corridors

Office-to-office transitions in modern open-plans with floating floors

Luxury condos requiring disclosure of acoustic ratings

Classrooms and institutional buildings with suspended or modular floors

What Distributors Like Buldix Should Stock

IIC-rated underlayments with tested assemblies for all major floor types

Rubber and cork rolls in multiple thicknesses with matching tapes or adhesives

Tile-compatible sound mats for mortar-bed installs

Integrated moisture barrier underlays for slab-on-grade applications

Specification sheets with IIC/STC data, installation guides, and LEED documentation

Also offer training resources and acoustic consulting support for customers working on LEED, WELL, or code-sensitive projects.

Conclusion: Silence Isn’t Golden—It’s Required

In today’s buildings, sound control is a baseline expectation—not a luxury upgrade. Acoustic underlayment is a key component in meeting both occupant expectations and code requirements. The right product can mean the difference between passing inspection and tearing out a brand-new floor.

Distributors who offer IIC/STC-tested solutions—and help clients match underlayment to application—don’t just supply products. They deliver quiet, comfort, and compliance.