--- title: "Acoustic underlay: the layer that deserves a closer look" description: "Choose acoustic underlay by floor type, installation method and test evidence. Check thickness, moisture, star claims and strata approval before work." canonical: "https://monkeyfloors.com/acoustic-underlay" language: "en-AU" published: "2026-09-25" updated: "2026-09-27" --- # Acoustic underlay: the layer that deserves a closer look Quick answer Acoustic underlay helps reduce impact sound by introducing a resilient layer within the floor construction, but its performance depends on the finish, subfloor, ceiling and installation. Choose a compatible system with evidence relevant to your building, and check the exact acoustic requirement before treating a thickness or star label as proof of approval. By [Monkey Floors editorial team](https://monkeyfloors.com/about) · Published 25 September 2026 · Updated 27 September 2026 · 4 min read ## At a glance Start with Floor type and installation method Compare Complete tested constructions and matching acoustic metrics Check separately Moisture, floor height, support and approval Useful next step Read the relevant material guide below Underlay disappears when the floor is finished. Its specification should be settled long before that happens. Begin with the finish you intend to use and how it will be fixed. Then check the evidence for the whole construction. That gives you a useful shortlist before you consider the feel of a sample or the thickness printed on a roll. ## What does acoustic underlay do? A resilient layer helps isolate vibration from footsteps and other impacts. It is one part of a floor and ceiling system, alongside the finish, slab or supporting structure, ceiling and junctions. The [ABCB sound insulation handbook](https://www.abcb.gov.au/sites/default/files/resources/2022/Handbook-sound-transmission-insulation-in-buildings.pdf) explains isolation as a way to control structure-borne sound. Floor build-up and impact path. An impact meets the floor covering and underlay. Energy can travel through the supporting structure and radiate sound into the room below. This is a schematic, not a tested construction. Floor build-up shown schematically. The whole construction matters. There are three different questions to keep apart: - How does walking sound to someone in the room? - How much impact sound reaches the apartment below? - How much airborne sound, such as speech, passes between the rooms? A comfortable sample underfoot answers none of these on its own. If voices or music are the main problem, start with the [soundproof flooring guide](https://monkeyfloors.com/soundproof-flooring) before choosing an underlay. ## Which underlay guide matches your floor? Choose the underlay investigation that matches your proposed floor | Proposed finish | First decision | Information to obtain | | --- | --- | --- | | Hybrid or rigid-core boards | Whether a separate layer is permitted | Attached backing, permitted support and full installation instructions | | Laminate | The compatible floating-floor system | Underlay specification, moisture detail and joint support | | Engineered or solid timber | Floating, bonded or supported on a sheet layer | Fixing detail, adhesives, moisture provisions and acoustic report | | Tiles | The specified tile assembly | Mat, adhesive, any screed, movement details and wet-area design | | Carpet | Carpet and underlay as a combination | Intended-use class, backing, installation method and acoustic evidence | Read the detailed guides for [hybrid](https://monkeyfloors.com/acoustic-underlay/hybrid), [laminate](https://monkeyfloors.com/acoustic-underlay/laminate), [timber](https://monkeyfloors.com/acoustic-underlay/timber), [tiles](https://monkeyfloors.com/acoustic-underlay/tile) or [carpet](https://monkeyfloors.com/acoustic-underlay/carpet). If you are comparing materials, see [rubber, foam and cork](https://monkeyfloors.com/acoustic-underlay/rubber). If two quotes name different brands, the [Regupol vs Damtec comparison checklist](https://monkeyfloors.com/acoustic-underlay/regupol-vs-damtec) helps you compare the documents. ## What do the acoustic numbers mean? A laboratory report and a completed-floor test answer different questions. [ISO 10140-3](https://www.iso.org/standard/79483.html) describes laboratory impact testing and warns that applying its results to a building requires allowance for other sound paths and site conditions. [ISO 717-2](https://www.iso.org/standard/69867.html) covers the rating of those measurements and of field measurements. When reading a report, distinguish an improvement figure such as ΔLw from a result for the tested construction such as Ln,w, or a field result such as L’nT,w. Copy the complete notation, including any adjustment term, rather than recording only “dB”. Use the [acoustic test report reader](https://monkeyfloors.com/tools/test-report-reader) to organise the figures. Our [ratings guide](https://monkeyfloors.com/acoustic-ratings-explained) explains their direction and limits. Do not subtract a brochure improvement from an unrelated building result to predict a pass. ## Does a 5 star or 6 star label settle the choice? Ask which rating scheme the label refers to and what was assessed. The [AAAC explanatory note](https://aaac.org.au/resources/Documents/Public/AAAC%20Guideline%20for%20Apartment%20and%20Townhouse%20Acoustic%20Rating%20-%20Explanatory%20Note%20V2.0.pdf) makes clear that an isolated product cannot guarantee an AAAC rating. For a useful answer, request the report identifying the floor finish, underlay, structure and ceiling. Establish whether it records a measurement, a prediction or a professional opinion. Ask an acoustic consultant to explain any differences between that construction and yours. ## How much thickness can the floor accept? Treat thickness as a dimension to check, not an acoustic ranking. The [ATFA underlay guidance](https://www.atfa.com.au/uncategorized/installation-over-acoustic-underlays-consumer/) notes that equal-thickness products can have different properties and performance. Prepare a section through the proposed floor. Include the finish, attached backing, separate underlay, adhesive, preparation and any supporting sheet or screed. Compare the finished height with the surface being removed. The [floor-height calculator](https://monkeyfloors.com/tools/floor-height-calculator) can organise the arithmetic; the installer still needs to check the actual doors, thresholds and junctions. ## What needs attention during installation? Ask for a written sequence covering preparation, moisture assessment, permitted layers and perimeter details. Underlay is not a reason to skip checks on the subfloor. The ABCB handbook warns that fixings through an isolated floor into the slab can reduce the benefit of the resilient layer. Ask how trims, door stops and other fixed items will be detailed. For timber systems, obtain the agreed movement allowance rather than improvising a sealant repair. Keep moisture control separate from acoustic performance. A sound-reduction claim does not identify the required moisture treatment. Request the moisture test results and the proposed vapour or waterproofing detail appropriate to the floor and room. ## What should you keep for strata approval? Obtain the registered by-laws or rules and the approval process before committing to a system. Use the [strata flooring checker](https://monkeyfloors.com/tools/strata-flooring-checker) to organise questions for your building. - Exact flooring and underlay names, thicknesses and installation method - Complete acoustic report, including its date, test basis and construction - Written compatibility of the flooring, underlay, adhesives and moisture provisions - Drawing or description of perimeter and threshold details - Written approval conditions and any testing requirement - Photos and records of the layers before they are covered If the underlay changes after approval, submit the revised system for assessment before installation. A similar-looking roll is not enough to show that the approved construction has been retained. ## In this section Underlay ### [Acoustic underlay for hybrid flooring: getting the layers right](https://monkeyfloors.com/acoustic-underlay/hybrid) Check whether your hybrid floor permits extra underlay, how its backing was tested, and what to record for moisture, height and apartment approval. 4 min read Underlay ### [Acoustic underlay for timber: a complete floor specification](https://monkeyfloors.com/acoustic-underlay/timber) Choose acoustic underlay for floating or bonded timber by checking the full system, moisture, fixing details, floor height and apartment test evidence. 4 min read Underlay ### [Acoustic underlay for tiles: sound, height and wet areas](https://monkeyfloors.com/acoustic-underlay/tile) Plan acoustic underlay beneath tiles with a complete floor detail. Check tile support, test evidence, waterproofing, thresholds and apartment approval. 5 min read Underlay ### [Acoustic underlay for carpet: comfort with a clear specification](https://monkeyfloors.com/acoustic-underlay/carpet) Choose carpet underlay for comfort, intended use and acoustic evidence. Understand AS 4288 classes, carpet labels, backing, stairs and strata records. 5 min read Underlay ### [Rubber acoustic underlay: choosing the right construction](https://monkeyfloors.com/acoustic-underlay/rubber) Compare rubber acoustic underlay with foam and cork through system compatibility, tested construction, finished height and practical installation checks. 4 min read Underlay ### [Regupol vs Damtec: comparing the complete systems](https://monkeyfloors.com/acoustic-underlay/regupol-vs-damtec) Compare Regupol and Damtec proposals through the specified floor, test construction, compatibility and installation scope before choosing an underlay. 4 min read Underlay ### [Acoustic underlay for laminate flooring](https://monkeyfloors.com/acoustic-underlay/laminate) Choose laminate underlay by board compatibility, moisture requirements and complete-system acoustic evidence, with practical checks before installation. 3 min read ## Questions, answered ### Does acoustic underlay work? A suitable resilient layer can reduce impact transmission through a floor. The result depends on the whole construction and its installation. It does not promise silence, and an impact test does not establish how well the building blocks voices or music. ### Is thicker acoustic underlay always better? Thickness alone does not establish acoustic performance or suitability. Match the proposed underlay to the floor finish, fixing method and tested assembly, then check the height available at doors and thresholds. ### Can I use two acoustic underlays together? Do not add another layer unless the flooring and underlay suppliers accept the combined construction in writing. Ask for evidence for that arrangement, including any attached backing already on the board. ### Does a 6 star underlay guarantee strata approval? No. An underlay label cannot establish the completed building result or replace your scheme documents. Ask what the claim refers to, obtain the complete report and have its relevance to your proposed floor checked. ### How should I compare underlay quotes? Give each installer the same room plan, floor finish, preparation requirements and acoustic target. Ask each quote to name the full system and identify exclusions such as levelling, trims, moisture work and testing. ### Is underlay from a hardware store suitable for an apartment? The sales channel does not establish suitability. Use the same checks for any offer: exact product, compatibility, complete acoustic evidence and the requirements of your building. ## Sources 1. [Installation over acoustic underlays (consumer information)](https://www.atfa.com.au/uncategorized/installation-over-acoustic-underlays-consumer/) · Australasian Timber Flooring Association · Accessed 2026-09-27 2. [Sound transmission and insulation in buildings handbook, Version 4.0 (March 2021)](https://www.abcb.gov.au/sites/default/files/resources/2022/Handbook-sound-transmission-insulation-in-buildings.pdf) · Australian Building Codes Board · Accessed 2026-09-27 3. [ISO 10140-3:2021, laboratory impact sound insulation, published scope](https://www.iso.org/standard/79483.html) · International Organization for Standardization · Accessed 2026-09-27 4. [ISO 717-2:2020, rating of impact sound insulation, published scope](https://www.iso.org/standard/69867.html) · International Organization for Standardization · Accessed 2026-09-27 5. [AAAC Apartment and Townhouse Acoustic Rating, Explanatory Note V2.0 (May 2023)](https://aaac.org.au/resources/Documents/Public/AAAC%20Guideline%20for%20Apartment%20and%20Townhouse%20Acoustic%20Rating%20-%20Explanatory%20Note%20V2.0.pdf) · Association of Australasian Acoustical Consultants · Accessed 2026-09-25 ## Goes well with Ratings ### [Flooring acoustic ratings explained: read the whole result](https://monkeyfloors.com/acoustic-ratings-explained) Read flooring acoustic ratings with confidence: laboratory and field results, IIC, impact sound levels, AAAC stars and the evidence a by-law needs. 13 min read Apartments ### [Best flooring for apartments: quiet, finish and fit](https://monkeyfloors.com/guides/best-flooring-for-apartments) Choose apartment flooring around sound, appearance, installation and scheme approval, with evidence to compare carpet, timber, laminate and hybrid. 25 min read Strata rules ### [Strata flooring rules: a clear route to a considered floor](https://monkeyfloors.com/strata-flooring-rules) The NCC sets floor sound ratings for new buildings; your registered by-laws decide what you must do. Compare NSW, QLD and VIC rules and approval steps. 12 min read