Soundproof flooring: a quieter home, from the floor up

Quiet at home might mean fewer heel clicks in a living room or less footfall reaching the bedroom below. Those are different problems, even when they start at the same floor.

There is no floor finish that makes a room silent. Start with the noise you hear and the structure carrying it. Then choose the floor, underlay and installation details that address that path.

What does “soundproof flooring” actually mean?

Noise gets into the room below in two ways. Impact noise starts when something hits the floor: footsteps, a dropped pan, a chair dragged across boards. The hit makes the structure vibrate, and the ceiling below gives that vibration off as sound. Airborne noise starts as sound in the air, such as voices, TV and music, and has to push its way through the floor or walls.

The two need different fixes. The ABCB sound handbook (Appendix B.2) says structure-borne sound “cannot be attenuated by barriers or walls but requires the isolation of the vibration itself”, using “a resilient element such as rubber, neoprene or springs”. Carpet and acoustic underlay are resilient elements. For airborne noise the handbook (section 3.4.1) points to mass: added mass is “particularly effective in reducing airborne noise”.

So a floor mostly fixes the first problem and barely touches the second: an underlay and a floor finish weigh very little next to a concrete slab. The Australasian Timber Flooring Association (ATFA) says noise from talking and televisions “is controlled by mass of the floor system”, and that over a concrete slab “the mass of the slab generally provides sufficient control for this not to be a problem”. Footsteps are the hard part, because they vibrate “the whole structure including the slab and walls”.

Spec sheets and by-laws use a few ratings. Ln,w is impact noise through a floor measured in a laboratory, and L’nT,w (often written LnT,w) is impact noise measured in a real building; for both, lower is quieter. ΔLw is how much an underlay improves a standard bare floor in a laboratory; higher is better. Rw + Ctr and DnT,w + Ctr are the airborne ratings, laboratory and on site, where higher is better. The impact figures are defined in AS ISO 717.2:2024 and used in NCC Part F7; see acoustic ratings explained for each one.

Why does a concrete slab behave differently from timber joists?

On a concrete slab, the slab’s weight stops most airborne noise. Footsteps are the problem: a hard finish fixed straight to the slab passes each impact into the concrete, and a thicker slab helps but does not solve it. In a 2014 South-East Queensland field study, bare 180 mm slabs with no ceiling measured L’nT,w 68 to 76 on site, and bare 200 mm slabs measured 65 to 69. Both are worse than the NCC’s on-site limit of 62, so a bare slab needs something resilient on top or a ceiling underneath.

On timber joists, the structure is light. There is little mass to stop airborne noise, and footsteps travel through the boards and joists themselves. The ABCB handbook (section 3.2.2) recommends a break in the floorboards and joists between units to “control structure-borne noise intrusion from footsteps”, which shows how readily the frame carries them. So a timber floor needs work on both kinds of noise, mostly below the boards.

The AAAC explanatory note (May 2023) makes the same point: a test of a hard timber floor on acoustic underlay above a concrete slab “will be very different” to the same floor and underlay above “a joisted timber floor with plasterboard ceiling”. Never use a slab test to choose a floor for a timber-framed building, or the other way round.

Is soundproofing a house floor different from an apartment floor?

Yes. You are protecting different people, and only one of them has the law behind them.

In a house, the floor usually sits over your own living room or bedroom. The NCC’s sound rules for houses are in Volume Two, and the ABCB handbook (section 2.5) says they cover walls separating attached dwellings, such as townhouses. They set no sound rating for the floors inside your own home. You set the target, and you decide what is worth the money.

In an apartment, you are protecting a neighbour, and a code and a by-law stand behind them. Clause F7D5 of NCC 2022 Volume One says a floor between sole-occupancy units in a Class 2 or 3 building must have “an Rw + Ctr (airborne) not less than 50 and an Ln,w (impact) not more than 62”. Those are laboratory figures. The performance requirement in clause F7P1 sets on-site figures: a DnT,w + Ctr of at least 45 and an L’nT,w of no more than 62. NCC 2025 keeps the same figures.

The code is a minimum, not a target. Queensland’s appeal tribunal said in McLeod v Body Corporate for Stradbroke Tower and Villas [2015] QCATA 146 at [29] that the BCA “is a minimum construction standard” and “does not set levels for the purposes of good neighbourly relations”. Many buildings write a stricter figure into their by-laws, often in AAAC star terms. The AAAC guideline sets on-site impact figures of L’nT,w below 55 for 3 star, below 50 for 4 star, below 45 for 5 star and below 40 for 6 star, so the NCC’s 62 sits between 2 and 3 stars. Your building’s figure is in its by-laws; our strata flooring rules guides explain them state by state. Whether replacing a floor finish in an existing apartment must itself meet Part F7 is a question for a building certifier; the by-laws apply either way.

How should you compare floor types for impact noise?

The table compares floor constructions and evidence to request. Published examples come from different buildings and assemblies; they do not rank material categories or predict a result for your home. Keep each metric, construction and limitation beside the number.

For scale, the ABCB handbook (section 5.1.1) says replacing carpet with a hard floor “can result in as much as 25 to 30 dB extra sound transmission”, and the AAAC guideline puts 3 star at L’nT,w below 55, 4 star below 50 and 5 star below 45.

Sources: the carpet and floating timber results are from a Brisbane tower, set out in Body Corporate for Admiralty Towers II v Johnson [2017] QCATA 29 at [12]. The deemed carpet floor is clause S28C8(3) of Specification 28. The laminate results come from Jiang v Sui [2023] NSWCATCD 127 and The Owners Strata Plan No 7704 v Kim [2023] NSWCATCD 39. The tile and bare-tile results come from the Inter-noise 2014 study, which also found vinyl of 3 to 9 mm on underlay improved on the bare slab by 8 to 21 points, and from 18 Kingsford Street [2016] QBCCMCmr 78. The board and tile notes are from the ATFA information sheet.

Choosing for an apartment? See the best flooring for apartments and acoustic hybrid flooring.

Why does the underlay do most of the work on a slab?

On a slab, the concrete already handles airborne noise. The job left is to stop impacts reaching the concrete, and the underlay is the only resilient layer in the build-up. In the Inter-noise 2014 study, floating timber on underlay improved on the bare slab by 15 to 22 points, while tile stuck straight to the slab improved it by 0 to 2.

Underlay data sheets usually quote ΔLw. Under AS ISO 717.2:2024, the Australian adoption of ISO 717-2, it is the difference in impact level on a standard bare heavy reference floor without and with the covering, measured in a laboratory, and higher is better. It is good for comparing underlays, but it is not your floor’s rating, and you cannot subtract it from your building’s figure: in the Inter-noise 2014 case study, the same five underlays improved a bare slab by 4 to 17 points with no ceiling, but by 4 to 11 points once a plasterboard ceiling was added. The AAAC explanatory note goes further: no single product, “especially an acoustic underlay”, is guaranteed to reach a rating or star level on its own.

Installation matters as much as the product. The ABCB handbook (section 4.4) warns that nails and screws through a rubber underlay “diminish its performance”, and that isolated floors “should not be installed in contact with side walls”. Our acoustic underlay guide compares types by floor.

How do you soundproof an existing floor without replacing it?

Rugs and runners

A thick rug on a rug underlay softens footsteps where people walk most. The ATFA information sheet lists rugs and runners in high-traffic areas, and soft-soled footwear, among factors that “can have a profound effect on the actual noise transferred”. The limit is coverage: hallways, kitchens and room edges stay hard. In Beau Monde [2011] QBCCMCmr 548, a Queensland adjudicator ordered rugs on the walked tiled areas within 30 days, and also ordered the owner to take sufficient steps within six months, including replacing the tiles or laying carpet and underlay over them if necessary. Rugs are a first step, not the fix.

Refit the underlay under a floating floor

A floating floor is not glued or nailed to the slab, so the underlay under it can be changed. If it sits on thin foam, an installer can lift the boards, lay a tested acoustic underlay and relay them, with a gap at every wall. Whether the boards survive being lifted depends on the product, so check with the installer and the maker first. Ask for a test on a build-up close to yours, because the ATFA says the same underlay gives different results under different floors. Thin underlay is a common weak point: in Sui v Jiang [2024] NSWCATAP 128, the appeal panel noted evidence that the underlay under the disputed laminate was only about 2 to 3 mm thick.

A glued floor or tiles have no underlay to swap. The options a Queensland adjudicator gave in 18 Kingsford Street were carpet and underlay over the tiles, carpet and underlay instead of the tiles, or “new tiles laid over an appropriate acoustic membrane”.

When the answer is the ceiling in the unit below

Sometimes the fix is underneath. The ABCB handbook (section 5.1.1) says the extra noise from swapping carpet for a hard floor “is difficult to reduce, and the use of resilient suspended ceilings becomes an important part of any design solution”. A resilient ceiling hangs on isolation mounts instead of being fixed hard to the slab, with insulation in the cavity. The NCC’s own deemed floor in clause S28C8(2) of Specification 28 is a 150 mm slab with 13 mm plasterboard on furring channels and isolation mounts, and 65 mm polyester insulation in the cavity.

In the Inter-noise 2014 case study, one layer of 13 mm plasterboard ceiling improved a bare 190 mm slab by 14 points, from L’nT,w 69 to 55. The handbook adds two warnings. Even with resilient ceilings and floors, a compliant system “may still transmit sound at 15 to 20 dB higher than the original carpet design”. And (section 5.1.2) a rated ceiling belongs in the original construction, because “there is no guarantee of access to the unit or dwelling underneath to retrofit later”. Downlights, air conditioning, vents and sprinklers each need acoustic treatment.

In an apartment, the ceiling is in the unit below and may not belong to either owner. Ask the body corporate or owners corporation in writing who owns it before anyone plans work.

What can you do about noise from upstairs neighbours?

Footsteps from upstairs are an impact noise problem, and impact noise is best controlled at its source: the floor finish and underlay in the unit above. That floor is the upstairs owner’s to fix. A ceiling on your side can help, but you cannot carry out work in their lot.

What you can do is use the rules. In NSW, section 153 of the Strata Schemes Management Act 2015 says an occupier must not use a lot in a way that “causes a nuisance or hazard to the occupier of any other lot”. In Queensland, section 167 of the Body Corporate and Community Management Act 1997 says an occupier must not use a lot in a way that “interferes unreasonably with the use or enjoyment of another lot”. Many schemes also have noise or floor coverings by-laws, and NSW Fair Trading and the Queensland body corporate commissioner set out a similar path:

1. Talk to the neighbour, and keep a dated record of the noise.
2. Ask the owners corporation or body corporate to act on the by-laws.
3. Use the free mediation service in NSW, or conciliation in Queensland.
4. Apply to NCAT in NSW, or for adjudication in Queensland.

Bring objective evidence. In Norbury v Hogan [2010] QCATA 27, the tribunal said the test is whether the activity would interfere unreasonably with “another lot owner of ordinary sensitivity”. In Felcher v The Owners Strata Plan No 2738 [2017] NSWCATAP 219, a complaint about a floating floor failed because the owner below provided “no expert evidence” and “no reports from an acoustic engineer or from a builder”. With a test, tribunals act: in Kim, NCAT ordered a laminate floor that missed its approval conditions treated to 50 LnT,w within 56 days. The strata flooring rules hub links to each state’s rules, including strata flooring rules in NSW and body corporate flooring rules in Queensland.

What actually helps in a timber joist house?

A timber-framed floor has no slab to lean on, so three things do the work, and they work together. All three come from the ABCB handbook.

• Mass. Heavier layers resist airborne noise. Section 3.4.1 says an extra skin, such as “an additional layer of plasterboard with a cavity”, can “effectively reduce sound transmission”, and that deeper cavities work better. In practice that means a thicker or doubled plasterboard ceiling.
• Decoupling. Break the path the vibration takes. Section 4.5.2 says that in timber construction “it is good practice to install walls and ceilings on isolation mounts to improve impact isolation between floors”. A resilient underlay decouples the floor from above; isolation mounts decouple the ceiling from below.
• Absorption. Insulation in the joist cavity soaks up sound. Section 3.4.2 says the sound insulation of “a lightweight building element can be improved by introducing sound absorption into cavities”, with materials such as glass wool, rock wool or polyester.

The NCC shows the three working together. Clause S28C10(2) of Specification 28 deems a floor of 19 mm particleboard on 190 x 45 mm joists, with R2.5 insulation, isolation mounts and two layers of 16 mm fire-protective plasterboard, to meet Rw + Ctr 50 and Ln,w 62. That is the apartment standard, reached with mass, decoupling and absorption instead of a slab. In a house most of this work happens from below, so the easiest time is when the ceiling is coming down anyway.

How do you get comparable quotes?

Ask for itemised quotes against the same scope so the difference between them is clear:

• Get at least three quotes for the same build-up: the same floor, the same underlay make and thickness, the same area.
• Ask each quote to itemise removal of the old floor, slab preparation and levelling, the underlay, perimeter isolation, skirtings and trims, and door trimming.
• Ask whether an on-site acoustic test is included, who carries it out, and what happens if the result misses the by-law figure.
• For a ceiling, ask for the mounts, insulation and plasterboard in writing, and how downlights and vents will be treated.
• Ask which figure the quote is built to: the NCC minimum, or the figure in your by-law.

What should you ask a supplier or builder?

• What impact rating does this floor achieve, and is it a laboratory Ln,w, an underlay ΔLw or an on-site L'nT,w?
• Can I see the full test report, not a brochure figure?
• What was the tested build-up: floor, underlay and its thickness, slab thickness, and the ceiling below?
• Who carried out the test, who paid for it, and is the lab NATA-accredited or the consultant an AAAC member firm?
• Does the test match my building: concrete slab or timber joists, and the same kind of ceiling below?
• Will you leave a gap at every wall and skirting, with no nails or screws through the underlay?
• Do the flooring maker and the underlay maker both accept this combination in writing, with warranties intact?
• Can we lay a sample and test it on site before the whole floor goes down?
• If the finished floor is tested and misses the required figure, what will you do?

The sample test is the AAAC’s own advice: its explanatory note calls installing a sample in situ and testing it “the commonly accepted acoustical method”, and says the finished floor should be tested for certainty.

If the sound is a click or creak within your own floor, start with the floor-noise diagnosis guide. If you need evidence of sound reaching another apartment, read about the post-installation acoustic test.

For a click or creak within your own floor, start with the floor-noise diagnosis guide. For evidence of sound reaching another apartment, read about the post-installation acoustic test.