NCC Acoustic Compliance for Timber Floors
This technical reference outlines the acoustic performance requirements for timber flooring installations in buildings governed by the National Construction Code Volume 1.
Applicable Standards
- NCC Volume 1, Part F5: Sound insulation requirements for Class 2-9 buildings
- AS/ISO 717.1: Airborne sound insulation rating (Rw + Ctr)
- AS/ISO 717.2: Impact sound insulation rating (Ln,w)
- AS/NZS 3837: Sound insulation assessment methodology
Performance Thresholds
| Measurement | NCC Minimum | Best Practice |
|---|---|---|
| Airborne (Rw + Ctr) | ≥ 50 | ≥ 55 |
| Impact (Ln,w) | ≤ 62 | ≤ 55 |
Achieving Compliance with Timber Flooring
Solid timber flooring nailed directly to joists will not achieve the required impact sound insulation without additional acoustic treatment. The following systems provide compliant solutions:
System 1: Floating Engineered Timber
Engineered timber boards installed as a floating floor over acoustic underlay on concrete slab. Minimum 3mm rubber or cork underlay rated for the required Ln,w improvement. 10mm perimeter isolation gap with acoustic sealant.
System 2: Direct-Stick with Acoustic Adhesive
Engineered timber adhered to concrete slab using Bona R850 acoustic adhesive system. Provides both structural adhesion and sound attenuation. Suitable where floor height is constrained.
System 3: Resilient Batten System
Solid timber boards installed on resilient battens with acoustic isolation clips. Allows traditional nailed installation while achieving acoustic compliance. Higher cost but preserves solid timber option.
For acoustic underlay and adhesive systems, contact our trade desk on 1300 950 551.
What types of noise does acoustic underlay control in apartments?
There are two main noise types: high-frequency noise like music, voices, and TV which is controlled by floor system mass, and low-frequency vibrations like footfall and subwoofers which are controlled through acoustic underlays and isolation. Sound is measured in decibels with most people noticing a 3dB change. FSA Network floor sanders install flooring systems that meet building acoustic requirements.
What is the NCC acoustic requirement for floors between apartments?
The National Construction Code requires the Weighted Standardised Impact Sound Pressure Level (LnTw) to not exceed 62dB for floors separating dwellings. However, individual strata buildings may impose stricter by-laws, and some councils demand LnTw of 40-50dB. FSA Network floor sanders ensure timber floor installations comply with all applicable acoustic requirements.
How does timber flooring compare acoustically to carpet and bare concrete?
Bare concrete at 175mm thickness performs at approximately 70dB, timber on acoustic underlay typically achieves 50-60dB, and carpet flooring achieves approximately 40dB. Acoustic underlay systems typically provide 10-20dB noise reduction over bare substrate. Floor Sanding Australia can recommend acoustic underlay systems that meet your building's requirements.
Does concrete slab thickness affect floor acoustics?
Yes, concrete slab thickness significantly affects acoustic performance -- the difference between a 175mm and 150mm slab can be as much as 10dB. Thicker slabs provide better sound insulation as a base for timber flooring. FSA Network floor sanders consider slab thickness when recommending acoustic underlay systems.
Do thin laminates or thick hardwoods perform better over acoustic underlay?
Thin, flexible laminates actually perform better than thick hardwood floors over acoustic underlay because they conform more effectively to the resilient layer beneath. Acoustic underlay materials also vary significantly in performance despite having similar thicknesses. FSA Network floor sanders select the right combination of flooring and underlay for optimal acoustic results.
What impact does the 10dB acoustic reduction rule have on flooring choices?
A 10dB reduction sounds approximately half as loud to the human ear, and acoustic underlay systems typically provide 10-20dB noise reduction. This means the right underlay can make a timber floor sound half to quarter as loud as the bare slab beneath. FSA Network floor sanders help select the acoustic system that achieves the required noise reduction for your building.
What is the minimum 3dB change threshold for acoustic perception?
Most people notice a 3dB change in sound level, which is the smallest difference typically perceived by the human ear. This means acoustic improvements of less than 3dB are unlikely to be noticed by occupants. FSA Network floor sanders ensure acoustic underlay selections achieve meaningful noise reductions well above this perception threshold.