On this page
- What does carpet underlay contribute to a quieter room?
- Which underlay types and installation methods should you consider?
- What does an AS 4288 underlay class tell you?
- Do carpet stars mean acoustic stars?
- How should you read carpet acoustic evidence?
- What changes for stairs and carpet tiles?
- What should you record for an apartment?
Carpet brings softness to a bedroom, but the underlay still deserves a precise specification. Choose the combination for the room, the way it will be installed and the acoustic requirement.
If you are replacing existing carpet, keep a record of the old carpet and underlay before removal. That gives the installer and any acoustic consultant a clearer description of what is changing.
What does carpet underlay contribute to a quieter room?
The Carpet Institute of Australia describes two benefits: cushioning floor impacts and controlling reverberation within the room. These are related to different experiences. The sound of a chair scraping in your room is not the same assessment as impact transmission to the apartment below.
Carpet should not be described as a guarantee of silence. Ask what the available report measured and whether its construction resembles yours. The ABCB handbook, section 3.14, explains why changing from carpet to a hard finish can reduce impact isolation even when other acoustic work is undertaken.
If you are weighing that change, read replacing carpet with hard floors before deciding on appearance alone.
Which underlay types and installation methods should you consider?
The Carpet Institute’s underlay guidance identifies foam, latex, rubber and felt options. It also distinguishes installation methods, including carpet stretched over underlay, bonded systems and carpet tiles with integrated padding.
Ask the installer to specify a complete combination. A familiar material name does not confirm that it is accepted beneath the carpet you have chosen.
| Proposal | Ask the installer | Keep in the specification |
|---|---|---|
| Carpet stretched over underlay | Which underlay supports this carpet and the intended use? | Carpet, underlay, class and perimeter installation detail |
| A bonded carpet system | Which backing, underlay and adhesives are accepted together? | Layer order, adhesives and preparation requirements |
| Carpet tiles with integrated padding | What does the backing provide and how is it installed? | Exact tile and backing identification |
| Carpet tiles over a separate layer | Is that combination accepted and covered by the acoustic evidence? | Written compatibility and the complete installation detail |
For a replacement, ask whether the existing underlay will be assessed or replaced. If it is retained, record its identity and condition rather than assuming it matches the new carpet’s requirements.
What does an AS 4288 underlay class tell you?
The Carpet Institute describes five intended-use categories under AS 4288. They distinguish residential, luxury and commercial use. The light residential category, LR, excludes stairs.
Ask for the class suitable for the actual room and traffic. A bedroom, stair and office area with wheeled chairs should not be treated as the same specification merely because the underlay has the same thickness.
Keep that classification separate from a measured acoustic result. If an application asks for impact performance, request the relevant report as well as the underlay’s use classification.
Do carpet stars mean acoustic stars?
First identify the scheme. The Australian Carpet Classification Scheme bases its residential broadloom star grading on durability and appearance retention. It also describes separate high-performance labels for Appearance, Comfort and Luxury, with acoustic qualities included among the Comfort considerations.
Those labels should not be read as AAAC ratings of a completed apartment. Ask what the particular label establishes and obtain the acoustic evidence required for your project.
| Information | What it helps assess | What to request separately |
|---|---|---|
| Underlay use class | Suitability for an intended category of use | Compatibility with the chosen carpet and acoustic evidence |
| ACCS carpet grade or label | The qualities covered by that particular classification | Any required building acoustic assessment |
| Sound absorption figure such as NRC | Reverberation control in the room | Impact transmission evidence for the floor and ceiling |
| Impact test report | The tested assembly under the reported method | Assessment of differences from your proposed installation |
How should you read carpet acoustic evidence?
A useful report identifies the carpet, backing, underlay, installation method, supporting floor and ceiling. Check whether the result is measured in a laboratory or in a building.
ISO 10140-3 explains that laboratory measurements cannot be applied directly to a building without considering other influences. Keep the complete metric and any adjustment term when copying a result into an application.
The test report reader can organise those details. If the offer supplies only a room absorption figure, ask for the evidence relevant to impact sound below the floor.
What changes for stairs and carpet tiles?
For stairs, request the permitted carpet and underlay combination and the fixing detail. Confirm the underlay’s stair suitability before ordering the same roll for bedrooms and stairs.
For carpet tiles, identify the exact backing first. Establish whether the proposed system includes integrated cushioning, a separate underlay, or neither. Ask about permitted adhesives and the prepared substrate. Do not transfer the acoustic figure of one backing to another tile carrying the same face design.
What should you record for an apartment?
Read the actual building rules and approval conditions before assuming that a carpet replacement needs no further checks. Our strata flooring guide helps identify the documents to obtain.
The AAAC explanatory note cautions that a product alone cannot guarantee the building result. Keep the agreed carpet and underlay combination named in the records.
- Carpet product, backing and underlay identification
- Intended-use class and any stair requirement
- Installation method and written compatibility
- Relevant acoustic report and assessment of building differences
- Existing underlay condition if it is to be retained
- Written approval conditions and accepted substitutions
For the wider material decision, compare the flooring options for apartments. For underlays beneath other finishes, return to the underlay hub.
Questions, answered
What is the best acoustic underlay for carpet?
Select an underlay accepted for the carpet, room and installation method, then assess acoustic evidence for the complete combination. A use class or thickness does not establish the impact result in your building.
Is carpet with underlay quieter than a hard floor?
Carpet and underlay can reduce impact noise and room reverberation. Replacing carpet with a hard finish can reduce impact isolation. The result for a particular apartment still depends on its floor, ceiling and installation.
Is 10 mm carpet underlay better than 7 mm?
Thickness alone cannot answer that. Check the carpet compatibility, intended-use classification and acoustic evidence for each proposed combination. Ask the installer to explain the support and height requirements.
Does a carpet star label show its acoustic rating?
Check the scheme and label type. ACCS residential broadloom star grades describe durability and appearance retention; the scheme also has separate high-performance labels. None should be treated as an AAAC building rating or substituted for the required acoustic evidence.
Can carpet underlay be used on stairs?
Check the underlay classification and the carpet installation requirements for stairs. The Carpet Institute identifies the AS 4288 light residential category, LR, as unsuitable for stairs.
Do carpet tiles need a separate underlay?
Check the exact tile backing and accepted installation system. Some carpet tile constructions have an integrated pad. Do not add a separate layer without confirming that the proposed combination and adhesive are suitable.
Sources
- Carpet underlay · Carpet Institute of Australia · Accessed 2026-09-27
- Australian Carpet Classification Scheme · Carpet Institute of Australia · Accessed 2026-09-27
- Acoustic benefits of carpet · Carpet Institute of Australia · Accessed 2026-09-27
- Sound transmission and insulation in buildings handbook, Version 4.0 (March 2021) · Australian Building Codes Board · Accessed 2026-09-27
- ISO 10140-3:2021, laboratory impact sound insulation, published scope · International Organization for Standardization · Accessed 2026-09-27
- AAAC Apartment and Townhouse Acoustic Rating, Explanatory Note V2.0 (May 2023) · Association of Australasian Acoustical Consultants · Accessed 2026-09-25