Floor acoustics in multi-family housing · NRA 2000, ΔLw, what we install

In new-build multi-family housing, failed acoustic tests at handover almost always come down to impact noise — not airborne noise. The NRA 2000 regulation (Order of 30 June 1999) sets a maximum L'nT,w of 58 dB between superimposed dwellings. The lower the number, the better.

The three metrics that matter

DnT,w — airborne sound insulation between dwellings. Target: 53 dB. Governed by the mass of the concrete slab — the floor covering has almost no impact. L'nT,w — impact noise (heels, dropped objects). Target: 58 dB. This is the metric that drives floor choices. ΔLw — impact noise reduction by the floor system. Read on product datasheets. For multi-family housing, target ΔLw ≥ 18 dB.

ΔLw by floor type

Laminate + standard underlay: 16–18 dB (borderline) · Laminate + HD acoustic underlay: 19–22 dB · Click LVT + integrated underlay: 17–19 dB · Bonded acoustic LVT 5 mm: 17–20 dB · Engineered hardwood bonded on acoustic screed: 0 dB (acoustics from the screed) · Engineered hardwood floating + fibre underlay: 18–21 dB · Contract carpet tile: 22–28 dB (well above)

The classic trap: bonded hardwood on underfloor heating

In new-build projects with low-temperature underfloor heating (PCBT), the acoustic screed system — not the floor covering — delivers the ΔLw. The bonded floor is acoustically neutral. Avoid specifying "acoustic floor covering ΔLw ≥ 19 dB" when the screed already achieves 22 dB: it is redundant and excludes perfectly suitable hardwood or laminate options.

Site feedback: 24 buildings, 6 years

From 2020 to 2025 we completed 24 multi-family schemes in Savoie and Haute-Savoie. Acoustic tests at handover: 23 passed first time, 1 failed — the acoustic underlay had been substituted by the screeder for cost. Mean measured L'nT,w: 54.2 dB, 3.8 dB margin below the 58 dB threshold.