The Problem
In multifamily and mixed-use construction, the floor-ceiling assembly between occupancies has to control two kinds of sound: the thud of footsteps and dropped objects (impact noise), and voices, TVs, and music passing through the structure (airborne noise). The International Building Code sets minimum performance for both. Miss it, and the assembly fails inspection — which means rework, delays, and change orders.
IIC
Measures how well an assembly blocks impact noise — footsteps, dropped keys, rolling chairs — from transmitting to the space below. Tested per ASTM E492. Higher is quieter. This is the rating flooring most directly affects.
STC
Measures how well an assembly blocks airborne noise — speech, TV, music — from passing through. Tested per ASTM E90. Largely a function of the whole assembly, but the floor finish contributes.
What the Code Requires
Under the IBC, floor-ceiling assemblies separating dwelling units generally must achieve a minimum STC 50 and IIC 50 when tested in a laboratory (or 45 for certain field tests). Many owners, franchises, and premium developments specify higher. The floor you choose either helps you clear that bar — or forces the assembly to make up the difference elsewhere.
Minimum IIC & STC (IBC, lab-tested)
The number your submittal has to document — and the reason acoustic performance can't be an afterthought.
The Soundstop Advantage
The conventional way to hit an IIC target is to buy a floor, then buy and install a separate acoustic underlayment beneath it — another product to source, another line on the schedule, another install to inspect.
Soundstop's acoustic layer is built into the plank (BA-cored), so there's nothing separate to order or store.
No underlayment step. Crews lay the floor once, which protects the schedule and reduces labor cost.
Cite Soundstop's own test reports rather than assembling ratings from multiple vendors' products.
Before You Spec
Five questions worth answering on every project before the floor gets locked in.
Send your acoustical requirement and floor plan. We'll tell you exactly which Soundstop format and documentation to spec.
Note: acoustic requirements vary by jurisdiction, code edition, and whether ratings are tested in the lab or the field. This page is general guidance for planning — confirm the exact values your project must meet, and cite the current Soundstop test report in your submittal.