The underlay beneath laminate has to suit both the flooring and the building. Choosing it only by the largest acoustic number can leave the board’s support requirements or the moisture detail unresolved.
Start with the laminate installation guide, then assess the underlay options it allows. This page covers laminate; for boards with a factory-attached pad, read acoustic underlay for hybrid flooring.
Does laminate need an underlay?
Start with the exact product instructions and a written specification for the board and underlay together. ATFA’s acoustic-underlay guidance recommends checking the combined system with both suppliers. An acoustic label alone does not establish that a roll is suitable beneath your laminate.
Ask the supplier to name the proposed board and underlay together on the quotation. If the board already has backing, establish whether anything additional is allowed before ordering. Keep the written answer with the installation instructions.
Which acoustic figure matters?
An underlay data sheet may describe improvement on a reference floor, while your apartment’s requirement describes the finished installation. Those are different questions. The AAAC explanatory note warns against treating a single product as a guaranteed acoustic rating for a building.
| Report detail | What it helps establish | What remains to check |
|---|---|---|
| Underlay improvement, ΔLw | Improvement in the stated laboratory construction | Relevance to your floor and building |
| Laboratory floor result, Ln,w | The tested floor assembly | Differences from the installed building |
| Field result, L'nT,w | Performance in the building and rooms tested | Whether those conditions match your proposal |
Read the slab and ceiling descriptions before comparing numbers. A ceiling in one test and none in another can make a simple league table misleading. Use acoustic ratings explained or the report reader if the units do not match your requirement.
Does thicker underlay make a better floor?
Thickness is a dimension, not a complete performance description. Ask which underlays the board maker permits and what evidence supports the proposed choice. The ATFA guidance on acoustic underlays emphasises agreement from both the flooring and underlay suppliers on the installation system.
Do not use an extra soft layer to compensate for an uneven subfloor. Preparation and underlay selection are separate decisions. Ask the installer to report on the substrate first and identify any preparation needed against the laminate guide.
For a quote comparison, record four things on one line: board name, underlay name, thickness and fixing method. Place the report beside that line. This makes an undocumented substitution easier to spot.
What about moisture and the perimeter?
Establish whether the underlay incorporates the required moisture protection or whether a separate layer is specified. An acoustic label does not answer that question. Follow the maker’s instructions for the substrate, joins, penetrations and edges.
The perimeter also needs an intentional detail. Ask how the floor will meet skirting, cabinetry, door frames and adjacent surfaces without losing the movement provision. Do not copy a gap dimension from another product. Floating-floor expansion gaps explains what belongs on the room plan.
What should be agreed before the floor is laid?
Have the installer confirm the approved construction, including preparation, moisture layers and the exact underlay. In an apartment, give them the written approval and any acoustic conditions before work starts. Photograph concealed layers and retain the packaging labels or product records.
If a test after installation is part of the approval, agree the access, assessment and responsibilities in advance. A flooring order and an acoustic test booking are easier to coordinate before the rooms are occupied. Our test-process guide sets out the questions to resolve.
A considered laminate specification is not simply the thickest board and thickest underlay. It is a compatible construction with a clear purpose and enough evidence for the building in which it will be used.
Questions, answered
Can I reuse the old carpet underlay beneath laminate?
Do not assume it is compatible. Specify the underlay permitted by the laminate maker and inspect the subfloor after the old covering is removed.
Can I double two thin underlays to improve sound?
Only use a layered arrangement expressly accepted for the flooring system. Adding layers changes support as well as height and is not a substitute for an appropriate acoustic report.
What if the committee asks for a star rating?
Obtain the exact requirement in writing and ask for evidence appropriate to the completed floor in the building. A star claim on an underlay roll alone is insufficient.
Sources
- Installation over acoustic underlays · ATFA · Accessed 2026-09-27
- Apartment acoustic rating: explanatory note V2.0, May 2023 · AAAC · Accessed 2026-09-25