What flooring meets acoustic requirements in multifamily buildings (IIC and STC)?
IIC and STC are ratings of the whole floor-ceiling assembly, not the flooring alone. What the building code asks for, how to read acoustic data sheets, and which resilient floors and underlayments have tested results.
Short answer: the International Building Code sets a minimum of IIC 50 for impact sound and STC 50 for airborne sound between dwelling units (45 when tested in the field). Those ratings belong to the whole floor-ceiling assembly, not to the flooring alone, so specify a floor that has been tested in an assembly like yours, or add an acoustic underlayment approved by the flooring manufacturer. Among Yorkshore's floors, Floortress LVT reports IIC 66 and STC 67 in a tested assembly, Dinoflex rubber tiles reach IIC 56 to 59 at 8 mm, and Silver Knight Acoustic 7 sheet vinyl reduces impact sound by 19 dB.
IIC, STC and the other numbers on a data sheet
| Rating | What it measures | Test method | What the flooring changes |
|---|---|---|---|
| IIC (Impact Insulation Class) | Footfall and dropped-object noise through the floor-ceiling assembly to the unit below | ASTM E492, rated to ASTM E989; field version ASTM E1007 | A lot: the floor finish and underlayment are where impact sound starts |
| STC (Sound Transmission Class) | Airborne sound, such as voices and TV, through the assembly | ASTM E90, rated to ASTM E413 | Little: STC depends mainly on the structure and ceiling |
| ΔIIC or ΔLw | The improvement the floor covering adds over the bare structure | ASTM E2179 (ΔIIC) or EN ISO 717-2 (ΔLw) | This is the floor covering's own contribution |
| NRC (Noise Reduction Coefficient) | How much sound a surface absorbs inside the room | ASTM C423 | Resilient floors absorb little; echo is controlled by ceilings and soft finishes |
An IIC value on a flooring data sheet is only valid for the assembly it was tested in: slab thickness or joist type, ceiling, underlayment and finish. Ask for the full assembly description before comparing two products.
What Yorkshore's floors report
| Product | Type | Published acoustic data | Best fit |
|---|---|---|---|
| Floortress | 30 mil LVT, 3 mm; loose lay or glue-down | IIC 66 (ASTM E492 / E989) and STC 67 (ASTM E90 / E413) in the manufacturer's tested assembly; Class I fire (ASTM E648) | Residential corridors, lounges, units |
| Silver Knight Acoustic 7 | Heterogeneous sheet vinyl with acoustic backing, 3.2 mm | 19 dB impact sound reduction (ΔLw, EN ISO 717-2) | Corridors and amenity rooms that also need a welded, cleanable floor |
| Evolution | Recycled rubber tile | IIC 56 to 59 at 8 mm, with plenum (ASTM E492); NRC 0.05 | Amenity rooms, lounges, fitness studios |
| Walk Soft | Softer recycled rubber tile, 8 to 12 mm | IIC 59 at 8 mm (ASTM E492) | Corridors and areas where comfort underfoot matters |
| Nature's Collection | Cork-and-rubber tile, 4 to 8 mm | IIC 58 at 6 mm (ASTM E492); NRC 0.04 | Lounges, libraries, leasing offices |
The IIC, STC and ΔLw values above come from different tests and different assemblies, so they are not directly comparable. Values come from manufacturer documentation; confirm the current data sheet and tested assembly before specifying.
Where an acoustic underlayment fits
- Under LVT: an LVT-rated acoustic underlayment such as SoundGuard 3-in-1 or SoundGuard Pro adds impact isolation where the floor alone does not reach the target.
- Under tile: sound abatement membranes such as NAC SAM 3 and SuperSAM 125 go under porcelain and stone.
- Check compatibility first. The flooring manufacturer has to approve the underlayment for that product and installation method, or the warranty can be affected. Use the combined assembly's tested IIC, not the underlayment's figure alone.
Space by space
| Space | Acoustic priority | Usual approach |
|---|---|---|
| Corridors over units | Impact noise from footfall, carts and move-ins | LVT or sheet with tested IIC, or with an approved acoustic underlayment |
| Amenity lounges and leasing offices | Impact noise to units below; room echo | Rubber or LVT with tested IIC; control echo with ceilings and soft furnishings |
| Fitness rooms | Dropped weights and machine vibration | Thick rubber tile such as Stride Fitness (interlocking, up to 2¾ in); confirm impact-isolation data for the actual weights and structure |
| Units | IIC and STC between dwelling units | A floor tested in a comparable assembly, or an approved underlayment; a loose-lay option such as Floorida+ speeds turnover |
Specification checklist
- Target IIC and STC from the adopted code edition, plus any condominium or owner requirements, which are often stricter.
- Lab ratings (ASTM E492, E90) for design; plan for field testing (ASTM E1007) if the project requires it.
- The tested assembly behind every acoustic figure: structure, ceiling, underlayment and finish.
- Underlayment approved by the flooring manufacturer for that product and installation method.
- Perimeter isolation: keep hard floors and underlayments from bridging to walls and pipes.
- Fire class (ASTM E648) for residential corridors and exits.
Yorkshore specifies flooring for apartment and condominium common areas across Florida and New England. See multifamily flooring and the guide to commercial LVT wear layers, or request samples with the acoustic data for your assembly.
Frequently asked questions
What IIC and STC ratings are required between apartments?
Is an IIC rating a property of the flooring?
What is the difference between IIC and Delta IIC (or Delta Lw)?
Does LVT need an acoustic underlayment in apartments?
What flooring works best for apartment fitness rooms?
Products to consider
-
Floortress Luxury Vinyl Plank and Tile
Heavy-duty 3 mm LVT with a 30 mil wear layer, in 7 x 48 in planks and 12 x 24 in tiles, loose lay or glue-down
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Silver Knight
Heterogeneous sheet vinyl with a self-disinfecting wear layer for healthcare and commercial interiors
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Evolution
Block-made recycled rubber tile in 70+ colours, 4 to 9 mm, for offices, schools, retail and libraries
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Walk Soft
Softer recycled rubber tile for corridors and standing work, 8 to 12 mm, square edge or interlocking
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Nature's Collection
Cork-and-rubber speckled tile in 4 to 8 mm for lobbies, libraries and classrooms
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Floorida Luxury Vinyl Plank
Waterproof rigid LVP, 8 x 48 in, 22 mil wear layer, in 2.5 mm glue-down and 5 mm loose-lay constructions
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Stride Fitness Tiles
Interlocking recycled rubber tiles for strength, free-weight and cardio areas
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