Underlay is the layer nobody sees, but it decides whether your laminate floor sounds hollow, feels springy, sweats in winter, or stays quiet and stable for 15 plus years. In New Zealand homes, where concrete slabs, old timber joists, heat pumps and coastal humidity all share the same floor, picking the right underlay matters as much as picking the right laminate.
This guide walks you through the four main underlay types sold in NZ, what each one is actually good for, and the subfloor checks you need to do before you buy. No marketing fluff, just what works.
Not sure which underlay suits your rooms?Talk to the Power Dekor team with your subfloor type and heating setup, and we will match you to the right spec.
Quick answer: what underlay do most NZ homes need?
For the majority of laminate installs over a concrete slab, you want a combination foam plus integrated moisture barrier, typically 2 to 3mm thick. Over a dry timber subfloor, a quality 3mm acoustic foam without a vapour layer is usually enough. If you have underfloor heating, you need an underlay that is explicitly rated low tog (thermally conductive), or the heat will be trapped below your floor instead of warming your room.
Those three scenarios cover most Kiwi renovations. The rest of this guide explains why, and what to do when your situation is less typical.
Why underlay matters more than people think
Laminate flooring is a floating system: the boards click together and sit on top of the underlay without being fixed to the subfloor. That means the underlay is doing four jobs at once:
- Cushioning small subfloor imperfections so the lock joints do not strain with every footstep
- Reducing foot noise, both inside the room and into the room below (important in double storey homes and apartments)
- Blocking moisture rising from a concrete slab into the board core
- Adding thermal comfort, so the floor does not feel cold in winter
Pick the wrong underlay and at least one of those jobs fails. Most underlay failures show up as hollow sounding boards, gapping at joints, or swollen edges from trapped moisture. All avoidable with the right spec.
The four underlay types you will see in NZ
1) Standard foam underlay (PE foam)
The entry level option. A thin polyethylene foam, usually 2mm, that provides basic cushioning and minor sound absorption. Works fine in bedrooms and low traffic rooms over a very dry, very flat timber subfloor.
Not recommended for concrete, not recommended for family living areas, and not recommended for two storey homes where noise transfer matters.
2) Combination foam with moisture barrier (PE plus PE film)
The most common residential choice in NZ. A foam layer bonded to a polyethylene film that acts as a vapour barrier. The foam handles cushioning and sound, the film blocks rising moisture from the concrete.
This is the default answer for most Auckland, Wellington and Christchurch concrete slab installs. Look for a product rated at a Sd value (vapour diffusion resistance) high enough for NZ concrete, and make sure the overlap seams are taped during installation.
3) Acoustic rubber or felt underlay
A denser, heavier underlay, often 3 to 5mm, made from rubber crumb, recycled felt, or rubber backed felt. Significantly better at blocking impact noise (footsteps) and airborne sound between floors.
Worth it in apartments, two storey homes, home offices above bedrooms, and anywhere strata or building code acoustic ratings apply. More expensive than foam, but the noise performance is measurable.
4) Underfloor heating compatible underlay
A low thermal resistance underlay (low tog rating) designed to let heat pass through efficiently. Many standard foam underlays trap heat and waste your heating system’s output.
If you have hydronic or electric underfloor heating, check the manufacturer’s maximum tog value (often around 1.0 tog combined with the floor) and match your underlay accordingly. Most underfloor heating compatible underlays are thinner, denser foams or felt composites.
What to check on your subfloor first
The underlay cannot fix a bad subfloor. Before you spend a dollar on laminate, run through this checklist:
Concrete slab checklist
- Moisture: Test the slab with a moisture meter. New slabs need 60 plus days of drying per 25mm of thickness before any floating floor goes down
- Flatness: 3mm deviation over a 2m straight edge is the usual threshold. Anything more needs self levelling compound
- Cracks: Hairline cracks are usually fine under an underlay. Structural or moving cracks need repair first
- Dust and debris: Fully vacuumed, no loose material
Timber subfloor checklist
- Structural integrity: No spongy boards, no rot, no insect damage
- Ventilation underneath: Check the crawlspace for airflow and moisture
- Existing finish: Old varnish or wax must be removed or levelled over
- Squeaks: Fix these before installing. The underlay will not hide them
If any of those checks fail, talk to your installer about remediation before buying materials. Retrofitting under a finished laminate floor costs three to four times as much as fixing it during prep.
Matching underlay to room type
Not every room in your house needs the same underlay. Here is how most NZ homes end up specced:
| Room | Recommended underlay | Why |
|---|---|---|
| Living room, open plan | Combination foam plus moisture barrier, 3mm | Cushioning plus acoustic comfort in the highest traffic zone |
| Bedrooms | Standard or combination foam, 2 to 3mm | Low traffic, comfort focused |
| Hallway, entry | Combination foam plus moisture barrier, firm density | High traffic, firmer underlay reduces joint stress |
| Kitchen | Combination foam plus moisture barrier, paired with water resistant laminate | Moisture protection is the priority |
| Upstairs floors | Acoustic rubber or felt, 3 to 5mm | Impact noise reduction into rooms below |
| Rooms with underfloor heating | Low tog underfloor heating rated underlay | Heat transfer efficiency |
For kitchens and busy family zones, the underlay is only half the story. The laminate itself needs to be moisture tolerant. See AquaRepel water resistant laminate flooring for the product side of that conversation.
Common underlay mistakes Kiwi homeowners make
After years of installs, the same five issues come up again and again:
- Doubling up underlay to “add comfort”. Two layers of foam is too soft. The lock joints flex, joints open, and boards fail early. Always a single layer at the specified thickness
- Skipping the moisture barrier on a concrete slab because the slab “looks dry.” Concrete always releases moisture. Always use a vapour barrier
- Using upholstery foam or carpet underlay as a cheap substitute. These are far too compressible for a click lock floor
- Ignoring the heating rating. Piling a thick acoustic underlay over underfloor heating wastes power and voids both floor and heating warranties
- Not overlapping and taping seams on a moisture barrier. Any gap lets moisture up through the seam, and damage concentrates right at the join
Fixing any of these after the floor is laid means lifting the entire floor. Get it right once, at prep stage.
Cost expectations for underlay in NZ (2026)
Underlay is priced per square metre and varies widely by type and brand. Rough retail ranges in 2026:
- Standard PE foam 2mm: NZD 3 to 5 per square metre
- Combination foam plus moisture barrier 3mm: NZD 6 to 12 per square metre
- Acoustic rubber or felt: NZD 12 to 25 per square metre
- Underfloor heating compatible: NZD 10 to 20 per square metre
On a 60 square metre living area, the difference between bottom end foam and a good combination moisture barrier underlay is about NZD 300 to 500. On a 20 plus year floor, that is not the place to save money.
Next step: get the right underlay matched to your floor
If you know your subfloor type (concrete or timber), your rooms, and whether you have underfloor heating, we can match you to a Power Dekor laminate plus the right underlay in one quote.
Browse the full laminate range on our products page, or go straight to premium laminate flooring for our higher spec options. For the underlay specific deep dive on when and why you need one, see our NZ underlay guide.
Ready for a shortlist?Contact Power Dekor with your rooms, subfloor and heating setup.
FAQs
Do I actually need underlay under laminate flooring?
Yes, almost always. Laminate is a floating system and the underlay handles cushioning, joint protection, moisture blocking and sound reduction. The only exception is laminate products with a pre attached underlay backing, which are installed directly on the subfloor.
What is the best underlay for laminate flooring on concrete in NZ?
A combination foam with integrated PE moisture barrier, typically 3mm thick. The foam cushions the floor, the film stops slab moisture reaching the board cores. Lay with overlaps taped, especially at seams.
Can I use the same underlay under underfloor heating?
Only if it is rated low tog. Standard thick foam underlay insulates the heat from reaching your room. Check the combined tog of your floor plus underlay and keep it below the heating manufacturer’s maximum (often around 1.0 tog).
How thick should laminate underlay be?
For most residential floors, 2 to 3mm is right. Thicker underlay does not mean better. Too soft an underlay lets the lock joints flex under foot traffic and shortens the floor’s life.
Does underlay reduce noise between floors?
Standard foam underlay reduces noise modestly. For real impact noise reduction between floors (footsteps heard in the room below), use a dense acoustic rubber or felt underlay, usually 3 to 5mm.
Can I reuse the existing underlay when I replace my laminate?
No. Underlay compresses permanently under a laminate floor over years of use. Always install fresh underlay with a new floor, otherwise the cushioning, sound and moisture performance will all be compromised.
Do I need a separate moisture barrier if my underlay already has one?
No. A combination underlay with an integrated PE film is the moisture barrier. Do not layer a second barrier on top, because trapped moisture between two impermeable layers is worse than no barrier at all.
What if my concrete slab is new?
Wait for it to dry. New slabs need roughly 60 days per 25mm of thickness to release construction moisture. A moisture meter reading, or a calcium chloride test, is worth the cost before installing any floating floor on a newer slab.