In a 2019 Korean government audit of 191 households in 28 newly built apartment complexes, 184 households (96%) had floors performing below the grade they had been certified for, and 114 (60%) failed the legal minimum outright (Board of Audit and Inspection of Korea, 2019 audit, reported by Kyunghyang Shinmun). That gap between a rated assembly and a lived-in floor is the thread running through this roundup. In the United States the code target is a laboratory IIC of 50, yet New York City alone logged 379,297 residential noise requests in 2024 (Office of the New York State Comptroller, NYC311 Monitoring Tool 2025), and 18.1% of people in the EU live in households reporting noise from neighbours or the street (Eurostat, EU-SILC sdg_11_20, 2023). We aggregated data from the International Code Council, the National Research Council of Canada, Eurostat, the COST Action TU0901 survey of European building codes, peer-reviewed field studies in Applied Acoustics and IJERPH, Forum Acusticum proceedings, and Korean ministry and audit data. Floor impact noise is the indoor cousin of the community exposure covered in our roundup on aircraft noise around airports: lower in level, but delivered through the ceiling of your own bedroom.
TL;DR
- US code minimum for floor-ceilings between dwelling units: IIC 50 in the lab, NISR 45 in the field (ICC, International Building Code 2021, Section 1206.3).
- A bare 150 mm concrete slab rates about IIC 28, against IIC 75 to 85 with carpet and underlay (NRC Canada, Construction Technology Update No. 35).
- A bare 5-ply cross-laminated timber floor rates IIC 25 (WoodWorks, Acoustics and Mass Timber 2021).
- L’n,w explained 26% of footstep annoyance across ten Swedish buildings; extending the rating down to 20 Hz raised that to 74% (Ljunggren et al., Applied Acoustics 2014).
- The new low-frequency impact rating uses the 50, 63 and 80 Hz bands, below the 100 to 3150 Hz range of IIC (LoVerde, Dong and Rawlings, Forum Acusticum 2023).
- National impact limits for multi-storey housing in Europe differ by more than 15 dB (Rasmussen and Machimbarrena, COST Action TU0901 2014).
- 18.1% of the EU-27 population lives in households reporting noise from neighbours or the street (Eurostat, EU-SILC sdg_11_20, 2023).
- NYC311 residential noise requests reached 379,297 in 2024, up 27.1% in one year (NYS Comptroller, NYC311 Monitoring Tool 2025).
- 68.6% of Korean on-site inter-floor noise diagnosis requests from 2020 to July 2025 cited walking or running (Korea Ministry of Environment data via Hankyung 2025).
- 96% of audited Korean apartment households had floors below their certified grade (Board of Audit and Inspection of Korea 2019, via Kyunghyang Shinmun).
1. The Code Floor: IIC 50 in the US, L’nT,w 62 in England and Australia
The US requirement is a laboratory number with a built-in discount. The International Building Code asks for IIC 50 under ASTM E492 but accepts NISR 45 when the finished floor is tested in the building (ICC, International Building Code 2021, Section 1206.3), a five-point allowance that accepts some loss to flanking paths and workmanship between the lab and the occupied unit. The 2024 edition keeps the same pair.
Other jurisdictions write the limit the other way round. England and Australia cap the impact sound level heard below (L’nT,w), so a lower number is better, while IIC rises as performance improves. Korea goes furthest on construction prescriptions, pairing a decibel ceiling with a minimum slab depth. Full requirement text sits in the IBC Chapter 12 sound transmission provisions and the UK’s Approved Document E.
| Metric | Value | Source |
|---|---|---|
| Lab minimum, floor-ceilings between dwelling units (ASTM E492) | IIC 50 | ICC, International Building Code 2021, Section 1206.3 |
| Field minimum (ASTM E1007) | NISR 45 | ICC, International Building Code 2021, Section 1206.3 |
| England, purpose-built flats: maximum impact level, separating floors | L’nT,w 62 dB | UK Approved Document E, 2015 edition, Table 0.1a |
| England, flats formed by material change of use | L’nT,w 64 dB | UK Approved Document E, 2015 edition, Table 0.1a |
| England, pre-completion testing rate | At least 1 set of tests per 10 dwellings in each group | UK Approved Document E, 2015 edition, para 1.30 |
| Australia, Class 2 and 3 floors between sole-occupancy units | LnT,w not more than 62 | ABCB, NCC 2022 Volume One, Part F7 (F7P1) |
| Korea, minimum floor impact performance for certified floor structures | 49 dB | Korea MOLIT, reported by News Seoul 2024 |
| Korea, minimum slab thickness (with mandatory floating floor) | 210 mm | Park and Lee, Noise and Health 2026 |
Context note: Australia’s performance requirement is set as a field value in the NCC 2022 Part F7, and Korea’s pre-approval system for floor structures dates from 2005, with post-construction checks added in August 2022 (News Seoul, 2024).
2. IIC of Common Assemblies: Concrete Slabs and Wood Joists
The finish matters more than the structure. A bare 150 mm concrete slab lands at roughly IIC 28, 22 points below the US code minimum, and carpet with underlay lifts the same slab to IIC 75 to 85 (NRC Canada, Construction Technology Update No. 35). On concrete, the floor covering does most of the work: switching from carpet to a hard surface can erase most of the rating.
Wood joist floors start in a better position than bare concrete but respond less to finishes, because their weakness sits in the low bands that toppings barely touch. Most recent available data: NRC Construction Technology Update No. 35 by A.C.C. Warnock, an undated update from the NRC Institute for Research in Construction that cites 1999 work; no newer public NRC summary of this scope was found.
| Metric | Value | Source |
|---|---|---|
| 150 mm concrete slab, bare or with ceramic or marble tile | About IIC 28 | NRC Canada, Construction Technology Update No. 35 |
| Vinyl flooring attached to a concrete slab | About +8 IIC points | NRC Canada, Construction Technology Update No. 35 |
| 35 mm concrete floated on 25 mm mineral fibre board, over 150 mm slab | IIC 60 to 65 | NRC Canada, Construction Technology Update No. 35 |
| Carpet and underlay on 150 mm slab | IIC 75 to 85 | NRC Canada, Construction Technology Update No. 35 |
| Basic wood joist floor, single-layer subfloor, no topping | About IIC 45 | NRC Canada, Construction Technology Update No. 35 |
| Each doubling of total joist-floor mass | About +7 IIC points | NRC Canada, Construction Technology Update No. 35 |
Outlier note: carpet’s very high rating reflects how well it cushions the steel hammers of the standard tapping machine, not how well it stops a heavy heel strike. Research into thinner low-frequency absorbers is tracked in our acoustic metamaterials roundup.
3. Lightweight and Mass Timber Floors: Where Footsteps Annoy Most
Mass timber has revived an old problem. A bare 5-ply cross-laminated timber floor rates IIC 25 and STC 41 (WoodWorks, Acoustics and Mass Timber 2021), half the code target, so every CLT residential floor depends on its topping, mat and finish to comply. The good news is that tested build-ups do clear the bar, and finished assemblies have passed IIC 60.
Occupant data shows why the rating alone is not the end of the story. Across ten Swedish multifamily buildings (four wood-framed, four CLT, one thin steel, one concrete), footstep noise drew the highest annoyance of any question, and the concrete building scored lowest. The full design guidance is in the WoodWorks mass timber acoustics paper.
| Metric | Value | Source |
|---|---|---|
| Bare 5-ply CLT floor | IIC 25 (STC 41) | WoodWorks, Acoustics and Mass Timber 2021 |
| Bare 7-ply CLT floor | IIC 30 (STC 44) | WoodWorks, Acoustics and Mass Timber 2021 |
| 2x6 nail-laminated timber floor with 1/2 in. plywood | IIC 33 (STC 34) | WoodWorks, Acoustics and Mass Timber 2021 |
| 5-ply CLT with 1 to 3 in. topping on acoustic mat, no finish floor | IIC 35 to 60 achieved | WoodWorks, Acoustics and Mass Timber 2021 |
| CLT topped assemblies with finish flooring | IIC 60+ achieved | WoodWorks, Acoustics and Mass Timber 2021 |
| Mean footstep annoyance, 10 Swedish buildings (0 to 10 scale) | 3.7, about twice the mean of the other questions (about 2) | Ljunggren et al., Applied Acoustics 2014 |
| Building-mean footstep annoyance: concrete building vs highest wood-framed building | 1.2 vs 6.3 | Ljunggren et al., Applied Acoustics 2014 |
Context note: questionnaire returns per Swedish building ranged from 13 to 79, so building means carry wide uncertainty. Most recent available data for the Swedish field survey: Ljunggren, Simmons and Hagberg, Applied Acoustics 85 (2014).
4. The Low-Frequency Blind Spot: Why IIC Misses Footfall
IIC was designed around a tapping machine, and the tapping machine is a poor stand-in for a person walking. In the Swedish field data, L’n,w explained only 26% of the variation in footstep annoyance, but adding a spectrum term that starts at 20 Hz raised it to 74% (Ljunggren et al., Applied Acoustics 2014). The thud that keeps people awake lives below the 100 Hz floor of the IIC calculation.
ASTM’s answer is a dual rating. The low-frequency impact insulation class (LIIC, ASTM E3207) looks only at 50 to 80 Hz, and the high-frequency rating (HIIC, ASTM E3222) at 400 to 3150 Hz, so a designer can see whether a floor fails on thuds or on clicks. The authors of the Forum Acusticum 2023 dual-rating paper state that existing single ratings do not adequately correlate with subjective reaction. Building services add another low-frequency path, covered in our roundup on subwoofer and HVAC low-frequency noise.
| Metric | Value | Source |
|---|---|---|
| Frequency range used by IIC and Ln,w | 100 to 3150 Hz | LoVerde, Dong and Rawlings, Forum Acusticum 2023 |
| Bands used by LIIC (ASTM E3207) | 50, 63 and 80 Hz | LoVerde, Dong and Rawlings, Forum Acusticum 2023 |
| Bands used by HIIC (ASTM E3222) | 400 to 3150 Hz | LoVerde, Dong and Rawlings, Forum Acusticum 2023 |
| 8-inch (200 mm) vs 6-inch (150 mm) concrete slab | About 5 LIIC points better on average | LoVerde, Dong and Rawlings, Forum Acusticum 2023 |
| Brand of resilient channel in otherwise similar wood truss assemblies | Up to 7 LIIC points difference | LoVerde, Dong and Rawlings, Forum Acusticum 2023 |
| Share of footstep annoyance explained by L’n,w (R2) | 26% | Ljunggren et al., Applied Acoustics 2014 |
| Share explained by L’n,w + CI,20-2500 (R2) | 74% | Ljunggren et al., Applied Acoustics 2014 |
Context note: the LIIC does not replace IIC and cannot be used to show code compliance; it is meant to be reported alongside the existing rating.
5. Europe’s L’n,w Patchwork: More Than 15 dB Between Neighbors
Europe never agreed on a single impact metric, let alone a single limit. The maximum difference between national impact sound limits for multi-storey housing exceeds 15 dB (Rasmussen and Machimbarrena, COST Action TU0901 2014), enough that a floor legal in one country would be clearly substandard across the border. The same survey counted 18 countries using L’n,w, 8 using L’nT,w and five with no regulatory requirement at all.
For a US reader, remember the direction: these are maximum received levels, so lower is stricter, the reverse of IIC. Most recent available data: the COST TU0901 chapter on existing requirements, with a data status of June 2013; individual national limits may have been revised since.
| Metric | Value | Source |
|---|---|---|
| Austria, multi-storey (strictest in survey) | L’nT,w not more than 48 dB | Rasmussen and Machimbarrena, COST Action TU0901 2014 |
| Denmark, Finland, Norway, Iceland and Germany, multi-storey | L’n,w not more than 53 dB | Rasmussen and Machimbarrena, COST Action TU0901 2014 |
| Sweden (spectrum term from 50 Hz included) | L’n,w + CI,50-2500 not more than 56 dB | Rasmussen and Machimbarrena, COST Action TU0901 2014 |
| England and Wales, and Ireland | L’nT,w not more than 62 dB | Rasmussen and Machimbarrena, COST Action TU0901 2014 |
| Spain | L’nT,w not more than 65 dB | Rasmussen and Machimbarrena, COST Action TU0901 2014 |
| Croatia (L’w) and Serbia (L’n,w), multi-storey | Not more than 68 dB | Rasmussen and Machimbarrena, COST Action TU0901 2014 |
Context note: Sweden is the only country in the survey table whose impact limit includes a spectrum term starting at 50 Hz, the direction the Swedish field study in section 4 argues should go further, to 20 Hz.
6. Neighbor Noise Complaints in Europe and the United States
Household surveys show that noise through floors and walls is a mass-market problem. 18.1% of the EU-27 population lived in households reporting noise from neighbours or from the street in 2023, only modestly below the 20.6% recorded in 2010 (Eurostat, EU-SILC sdg_11_20). The indicator bundles street and neighbor noise and captures what residents consider acceptable as well as actual levels, so the cross-country spread partly reflects expectations.
Building type shows up clearly in German survey data: apartment dwellers were nearly twice as likely as detached-house residents to be at least moderately annoyed by neighbor noise. In the US, the clearest public series is New York City’s 311 data, where residential noise was the second-largest request type in 2024; see the NYS Comptroller’s NYC311 report and the Eurostat noise indicator. For the people who mask what they cannot block, our white noise machine roundup tracks bedroom sound-machine use.
| Metric | Value | Source |
|---|---|---|
| EU-27 population in households reporting noise from neighbours or the street, 2023 | 18.1% (2010: 20.6%) | Eurostat, EU-SILC sdg_11_20 |
| Highest EU shares, 2023 | Malta 31.3%, Luxembourg 30.2% | Eurostat, EU-SILC sdg_11_20 |
| Below vs above the 60% at-risk-of-poverty threshold, EU-27 2023 | 20.9% vs 17.6% | Eurostat, EU-SILC sdg_11_20 |
| Germans disturbed or annoyed by neighbors’ noise | About 58% | Umweltbundesamt, Umweltbewusstseinsstudie 2024 |
| At least moderately annoyed by neighbor noise: apartment vs detached house, German survey (n = 1,940) | 27.4% vs 14.6% | Benz et al., IJERPH 2021 |
| NYC311 residential noise requests routed to NYPD, 2024 | 379,297 (+27.1% vs 2023; 232,848 in 2019) | NYS Comptroller, NYC311 Monitoring Tool 2025 |
| US renters rating soundproof walls as important (n = 172,703) | 88% | NMHC and Grace Hill, 2024 Renter Preferences Survey |
Math note: the Benz et al. shares are our sums of the “moderately”, “very” and “extremely” annoyed categories in the study’s Table 1 (apartments 1,532 respondents, detached houses 151). Germany’s 2023 Eurostat value (25.2%) is flagged as low reliability. The NMHC figure comes from NMHC’s summary of the survey and covers walls in general, not floors only.
7. South Korea: Inter-Floor Noise Complaints, Audits and Disputes
Korea publishes more floor impact noise data than any other country we reviewed, and the data is sobering. Between January 2020 and July 2025, 32,354 of 47,194 on-site diagnosis requests (68.6%) named walking or running as the cause (Korea Ministry of Environment data reported by Hankyung, 2025), the same footfall problem that IIC handles worst.
Complaint volumes jumped in 2020 and have eased since, but measured exceedances keep climbing, and the formal dispute route rarely ends in a settlement. Sources: Hankyung, 2025, Newsis, 2025 and Kyunghyang Shinmun on the 2019 audit.
| Metric | Value | Source |
|---|---|---|
| Complaints to the Inter-floor Noise Neighbor Center, 2012 | 8,795 | Korea Ministry of Environment data via Nocutnews 2021 |
| First-stage phone consultations, 2020 vs 2024 | 42,250 vs 33,027 | Korea Ministry of Environment data via Hankyung 2025 |
| Average phone consultations per day, 2020 to July 2025 (217,387 total) | About 106.6 | Korea Ministry of Environment data via Hankyung 2025 |
| On-site measurements exceeding the legal limit, 2020 vs 2024 | 18 vs 88 | Ministry of Climate, Energy and Environment data via Newsis 2025 |
| 2019 audit: households below the minimum performance standard | 114 of 191 (60%) | Board of Audit and Inspection of Korea 2019, via Kyunghyang Shinmun |
| 2019 audit: households with floors below their certified grade | 184 of 191 (96%) | Board of Audit and Inspection of Korea 2019, via Kyunghyang Shinmun |
| Dispute mediation applications settled, 2023 to 2025 | 13 of 148 (8.8%) | Korea Environment Corporation and LH data via MTN 2026 |
| Share of 2012 to 2020 on-site diagnosis cases citing walking or running (60,061 cases) | 67.6% | Korea Ministry of Environment data via Nocutnews 2021 |
Context note: the daytime limit for direct impact noise is now 39 dB (1-minute equivalent level), with 34 dB at night (Newsis 2025), down from 43 dB daytime and 38 dB night cited in 2021 (Nocutnews, 2021). At the time of the 2019 audit, the minimum standard was 58 dB for lightweight and 50 dB for heavyweight impact sound (Kyunghyang Shinmun 2019). The 2012 figure and the 2020 and 2024 figures come from differently scoped series (see Methodology).
Summary: Impact Insulation Class (IIC) by the Numbers
| Metric | Value | Source |
|---|---|---|
| US lab minimum, floor-ceilings between dwelling units | IIC 50 | ICC, International Building Code 2021, Section 1206.3 |
| US field minimum | NISR 45 | ICC, International Building Code 2021, Section 1206.3 |
| England, maximum impact level, purpose-built flats | L’nT,w 62 dB | UK Approved Document E, 2015 edition |
| Australia, Class 2 and 3 separating floors | LnT,w not more than 62 | ABCB, NCC 2022 Part F7 |
| Korea, minimum floor impact performance | 49 dB | Korea MOLIT via News Seoul 2024 |
| 150 mm concrete slab: bare vs carpet and underlay | IIC 28 vs IIC 75 to 85 | NRC Canada, Construction Technology Update No. 35 |
| Bare 5-ply CLT floor | IIC 25 | WoodWorks, Acoustics and Mass Timber 2021 |
| Footstep annoyance: concrete vs highest wood-framed building (0 to 10) | 1.2 vs 6.3 | Ljunggren et al., Applied Acoustics 2014 |
| Annoyance explained by L’n,w vs L’n,w + CI,20-2500 (R2) | 26% vs 74% | Ljunggren et al., Applied Acoustics 2014 |
| LIIC frequency bands | 50 to 80 Hz | LoVerde, Dong and Rawlings, Forum Acusticum 2023 |
| Maximum gap between European impact limits, multi-storey | More than 15 dB | Rasmussen and Machimbarrena, COST Action TU0901 2014 |
| EU-27 population reporting noise from neighbours or the street, 2023 | 18.1% | Eurostat, EU-SILC sdg_11_20 |
| Germans annoyed by neighbors’ noise | About 58% | Umweltbundesamt, Umweltbewusstseinsstudie 2024 |
| Moderately+ annoyed: apartments vs detached houses (Germany) | 27.4% vs 14.6% | Benz et al., IJERPH 2021 |
| NYC311 residential noise requests, 2024 | 379,297 | NYS Comptroller, NYC311 Monitoring Tool 2025 |
| Korea, first-stage inter-floor noise consultations, 2024 | 33,027 | Korea Ministry of Environment data via Hankyung 2025 |
| Korea, on-site requests citing walking or running (2020 to July 2025) | 68.6% | Korea Ministry of Environment data via Hankyung 2025 |
| Korea 2019 audit: households below minimum standard | 60% | Board of Audit and Inspection of Korea 2019, via Kyunghyang Shinmun |
| Korea, dispute mediations settled, 2023 to 2025 | 8.8% | Korea Environment Corporation and LH data via MTN 2026 |
Methodology and Sources
- International Code Council, International Building Code 2021, Chapter 12, Section 1206: IIC 50 (ASTM E492) and NISR 45 (ASTM E1007) requirements; the 2024 edition retains the same values.
- UK Government (GOV.UK), Approved Document E: resistance to the passage of sound, 2003 edition incorporating 2004, 2010, 2013 and 2015 amendments.
- Australian Building Codes Board, NCC 2022 Volume One, Part F7 Sound transmission and insulation.
- Korea Ministry of Land, Infrastructure and Transport, as reported by News Seoul (October 2024).
- Park and Lee, Psychological and Physiological Responses of Residents to Floor Impact Noise in Multifamily Housing, Noise and Health 2026 (commentary).
- A.C.C. Warnock, National Research Council of Canada, Construction Technology Update No. 35: Controlling the Transmission of Impact Sound through Floors.
- WoodWorks (Wood Products Council), Acoustics and Mass Timber: Room-to-Room Noise Control, R. McLain, 2021.
- Ljunggren, Simmons and Hagberg, Correlation between sound insulation and occupants’ perception, Applied Acoustics 85 (2014) 57-68.
- LoVerde, Dong and Rawlings, Design of Floor-Ceiling Assemblies Using Dual Ratings of Impact Noise Insulation, Forum Acusticum 2023.
- Rasmussen and Machimbarrena, Existing Sound Insulation Performance Requirements and Classification Schemes for Housing Across Europe, COST Action TU0901, 2014.
- Eurostat, Population living in households considering that they suffer from noise (sdg_11_20), EU-SILC.
- Umweltbundesamt, Nachbarschaftslärm und Lärm von Anlagen, citing the Umweltbewusstseinsstudie 2024.
- Benz et al., Contributors to Neighbour Noise Annoyance, International Journal of Environmental Research and Public Health 2021.
- Office of the New York State Comptroller, NYC311 Monitoring Tool, Report 3-2026, May 2025.
- National Multifamily Housing Council and Grace Hill, 2024 Renter Preferences Survey Report, as summarized by NMHC in Multifamily Dive.
- Korea Ministry of Environment data obtained by Rep. Kim Wi-sang, reported by Hankyung (October 2025).
- Ministry of Climate, Energy and Environment data obtained by Rep. Kim Wi-sang, reported by Newsis (October 2025).
- Korea Ministry of Environment and Korea Environment Corporation data, reported by Nocutnews (2021).
- Board of Audit and Inspection of Korea, apartment inter-floor noise audit (May 2019), reported by Kyunghyang Shinmun.
- Korea Environment Corporation and LH data analyzed by Rep. Cho In-cheol, reported by MTN (September 2026).
- Data watch: several anchor datasets are old and labelled as most recent available: the NRC assembly table (undated, citing 1999 work), the European requirements survey (data status June 2013; individual national standards may have been revised since), the Swedish field survey (2014) and the Korean audit (2019). Korean complaint figures come from differently scoped series: the 2012 value in the Nocutnews series counts center complaints, while Hankyung’s 2020 and 2024 values count first-stage phone consultations only (both series agree on 42,250 for 2020). The NYC Comptroller’s 379,297 counts NYPD-routed residential requests for calendar 2024, so tallies using other date windows or category definitions will not match. Eurostat’s indicator mixes neighbor and street noise and is published every three years, so the next value will be for 2026. We found no US federal survey that publishes a national estimate of noise heard through floors.
Last updated: October 18, 2026. We update this roundup quarterly, and the next refresh is expected when Eurostat publishes the 2026 EU-SILC noise indicator (sdg_11_20) and Korea’s Ministry of Climate, Energy and Environment releases full-year 2025 Inter-floor Noise Neighbor Center data.