You beat impact noise in a timber floor with three things at once: add mass, decouple the walking surface from the joists, and fill the cavity. Just stuffing insulation between the joists mostly helps against voices and the telly, not against footsteps. The biggest gain comes from a floating screed on top, or a decoupled ceiling on resilient bars underneath. And from closing the flanking paths, because your joist ends sit inside the wall and carry the sound straight around your insulation.
Hey DIYer,
You’re downstairs on the sofa. Upstairs, someone walks to the loo. And you don’t just hear that someone is walking, you hear which foot lands, whether they’ve got socks on, and whether they stop at the wardrobe on the way.
That’s impact noise. And a timber joist floor is brilliant at it.
I put up with it in my own house for years. Stuffed rock wool between the joists, closed the ceiling up feeling pleased with myself, and then discovered that the talking upstairs had indeed got quieter. But the footsteps? Exactly as loud as before. I’d solved the wrong problem.
That’s the mistake almost every article on this subject keeps alive: “fill the cavity with mineral wool” gets sold as the answer to noise nuisance. It isn’t. It’s one of three levers, and not the most important one.
Below you get the whole story: which noise you actually have, the physics behind it, what each solution costs in money, in height and in load capacity, and what you need to work out before you lift the first board.
First things first: which noise have you actually got?
Before you buy anything, you need to know what you’re hearing. The four types call for four different fixes, and most failed jobs happen because people tackle the wrong one.
| What you hear | What it’s called | What it travels through | What helps |
|---|---|---|---|
| Footsteps, chair legs, a dropped box of Lego | Impact noise | The structure itself, from above to below | Mass, decoupling, closing flanking paths |
| The hollow thud you hear yourself when you walk on your own floor | Walking noise | Air inside the floor build-up, in the same room | A dense, low-air underlay or extra mass |
| Voices, TV, music | Airborne noise | Air passing through the structure | Mass plus absorption in the cavity |
| Squeaking and creaking with every step | Creaking | Timber rubbing over nails or against itself | Screwing down and lubricating, not insulation |
Rows three and four get mixed up constantly. A shop sells you a “10 dB underlay” for walking noise, while that figure describes what the neighbour below hears. That’s something else entirely.
Rule of thumb: if you hear it in the same room, it’s walking noise. If the neighbours or your family hear it a storey down, it’s impact noise. The first needs a dense underlay, the second needs a completely different approach.
Why a timber floor in particular passes it on
A concrete floor slab easily weighs 300 to 500 kilos per square metre. A timber joist floor with softwood boards comes in around 40 to 60 kilos per square metre, ceiling included.
Mass is the biggest brake on sound. Heavy stuff is hard to set vibrating, light stuff is easy. That’s why you hear the neighbours upstairs in a 1930s house and hear far less in a 1970s concrete block.
On top of that come three things specific to timber:
1. The sound box. Between the floorboards and the ceiling sits an air cavity of 15 to 25 centimetres. Two thin, stiff panels with air in between: that is literally how a loudspeaker is built. The cavity amplifies certain tones instead of damping them.
2. Everything is rigidly connected. Floorboards are nailed or screwed to the joists. Step on a board and that vibration goes into the joist with no interruption at all, and the joist passes it on to the ceiling and to the walls.
3. The joist ends sit in the masonry. This is the path most people miss. The ends of your floor joists are built into the load-bearing wall. So a vibration in the joist also goes straight into the wall and comes back out again downstairs. That’s called flanking transmission, and it doesn’t care how neatly you finished your ceiling.
Point three is why people say, after an expensive floor job: “it’s a bit better, but it’s not gone.”
The three levers you can pull
Every serious solution is a combination of these three. The more you combine, the quieter it gets.
Lever 1: mass
More weight in the floor means less vibration from the same impact. This is the most predictable lever: you always get something back for it.
But timber has a limit. More on that below, because this is exactly where things go wrong.
Lever 2: decoupling
Make sure the layer you walk on no longer touches the joist directly. A springy layer goes in between: rubber, felt, wood fibre, mineral wool, or a metal resilient bar.
Decoupling is the most powerful of the three. Mass alone buys you a few dB, good decoupling buys a lot more. But it’s also the most unforgiving to build: one screw that accidentally goes through the resilient layer into the joist and your whole decoupling is gone. That kind of connection is called a sound bridge, and a single one can wipe out the gain from ten square metres of careful work.
Lever 3: absorption in the cavity
Damping the sound box by filling it. Soft, open fibrous materials like rock wool, glass wool, wood fibre or cellulose swallow the air vibrations in the void.
This works excellently against airborne noise and it improves what decoupling does. But on its own it does little against footsteps, because that vibration travels through the timber, not through the air.
For the fill, the rule of thumb is that you want the cavity at least 70 per cent full, evenly spread. Cramming it completely full isn’t necessary and actually works against you if it compresses a resilient layer.
Don’t pick a lightweight grade. Wool products for this application usually sit around 35 to 55 kilos per cubic metre. The extra dense stuff isn’t automatically better, but very light rolls slump over the years, and then your fill is a sound box again.
The biggest misconception: “I’ll just shove some wool in there”
Let me be blunt, because this is the heart of it.
Insulation between the joists does three things well: it damps airborne noise, it keeps heat between two floors that are heated differently, and it makes the cavity less resonant. Good job, do it.
But the vibration from a footstep goes through the timber. From the board into the joist, from the joist into the ceiling and the wall. That route doesn’t pass through the air in the void, so the wool barely touches it.
If you only do this and you’re hoping for quiet footsteps, you’re going to be disappointed. I know from experience, with a ceiling I built twice.
What do the rules say?
Handy to know what you’re being measured against, especially if you’re in a flat or planning to let it out.
New build between two dwellings. For separating floors, Dutch building regulations set a limit for the impact sound level of LnT,A of 54 dB maximum. The lower the number, the quieter. Measurement follows NEN 5077, with a standardised tapping machine on the floor above and a microphone in the room below. Source: NAA
If you’re building elsewhere, the numbers and the standard’s name will differ, but the method is the same everywhere: a standardised tapping machine above, a measurement below, one figure as the result.
Inside your own home there’s no requirement. Between your living room and your bedroom it can sound as hollow as it likes, as far as the regulations are concerned. That’s pure comfort, and that one’s your call.
In a leasehold or owners’ association it’s often written down. Deeds and house rules usually require a hard floor finish to improve impact sound insulation by at least Ico = +10 dB. Some associations demand +12 or +15 dB. That 10 dB figure originally comes from the era of short-pile carpet, which on average delivered roughly that improvement. Source: Rijssenbeek Advocaten
Ico and LnT,A are two scales for the same thing. They convert roughly via LnT,A ≈ 59 minus Ico. So Ico +10 dB works out at an LnT,A of around 49 dB. With Ico, higher is better. With LnT,A, lower is better. Don’t mix them up, because that’s exactly where arguments with the neighbours go off the rails.
The catch hidden in the certificate
There’s a gap here that almost nobody talks about, and it costs people money.
An underlay with a 10 dB certificate achieved that figure in one specific test build-up: a particular substrate, a particular underlay and a particular floor finish, measured together. Change one element and, strictly speaking, the certificate no longer applies.
And nearly all of those tests are run on a concrete floor, because that’s the standard test rig. Lay that same underlay on timber joists and you can get a completely different result. Often less, and in the low frequencies sometimes worse.
So what you do: with a timber substrate, explicitly ask for measurement data on a timber joist floor, not on concrete. If the supplier can’t provide it, don’t blindly assume you’ll meet the association’s requirement. When in doubt, have an acoustic consultant measure afterwards, or pick a solution with a healthy margin.
How much weight can your floor actually take?
This is the question nobody asks and the one that decides everything.
Timber floors in dwellings are designed for an imposed load of 1.75 kN/m², which is roughly 175 kilos per square metre. That covers everything: you, your sofa, your bookcase, your visitors. Where movable partitions are involved, another 0.50 kN/m² gets added in the calculation. Source: Houtinfo
If you’re adding a floating screed, that gets added permanently to the dead load of the structure. And that’s where it starts to pinch.
| Type of screed | Approximate weight | Suitable for timber joists? |
|---|---|---|
| Underlay plus laminate or vinyl only | 5 to 12 kg/m² | Almost always |
| Dry screed in gypsum fibreboard, 2 x 12.5 mm plus wood fibre | around 30 kg/m² | Usually, get it checked if unsure |
| Two layers of OSB or plywood on a resilient layer | 20 to 30 kg/m² | Usually |
| Anhydrite or sand-cement, 40 to 50 mm poured wet | 85 to 105 kg/m² | Usually NOT without a structural engineer |
The dead load of a complete floor build-up with a light dry floating screed sits around 0.55 kN/m². With a wet floating screed of 40 mm anhydrite it climbs to about 1.15 kN/m². That’s more than double, and it’s precisely why builders working on timber joists almost always go dry.
Practical limit: stay under 30 kilos per square metre of added weight and the risk in a sound joist floor is small. Head towards 60 kilos or more and get a structural engineer to look at it. That costs a few hundred euros and it prevents sagging floors, cracking ceilings and doors that stick.
Pay attention to the age of your house too. In a pre-1945 property the joists are often deeper in section but spaced further apart, and sometimes half a century of damp and woodworm has already gone over them. Before you start, take a look at the joist ends where they meet the wall: that’s where rot begins.
Five solutions, from light to heavy
Choose on the basis of three things: how much effect you need, how much height you can give up, and whether you can work from above or from below.
| Solution | Effect on impact noise | Height lost | Added weight | Guide price per m² |
|---|---|---|---|---|
| 1. Better underlay beneath the floor finish | Small to moderate | 3 to 10 mm | Negligible | 8 to 30 euros in materials |
| 2. Floating dry screed on top | Large | 30 to 60 mm | around 30 kg | 45 to 90 euros in materials |
| 3. Floor open, cavity filled plus decoupled floorboards | Moderate to large | 10 to 30 mm | 10 to 25 kg | 45 to 85 euros |
| 4. Decoupled ceiling on resilient bars | Large | 60 to 120 mm of ceiling height | On the ceiling | 40 to 80 euros in materials |
| 5. Floating floor plus decoupled ceiling | Very large | Both of the above | Both of the above | 100 to 170 euros in materials |
These are guide prices for materials if you do it yourself. Contracted out, floor soundproofing runs in practice towards 25 to 75 euros per square metre including installation, depending on whether you only fill the cavity or also lay a floating screed. Source: Isolatie-info
When do you choose what?
- Rented home or a small budget: option 1. Expect a comfort improvement, not a miracle.
- You’re replacing the floor anyway: option 2. By far the best ratio of effort to result.
- The floor is open for pipework: option 3, and combine it with option 2 if you’ve got the height.
- Other people live above you and you can’t get up there: option 4, from below.
- Bedroom above the living room and you want it genuinely quiet: option 5.
Step by step: laying a floating dry screed
This is the job with the best return. Reckon on a weekend for 20 square metres with two of you.
1. Do the height sums. Add up: resilient layer plus screed plus floor finish. That’s what you’re gaining in height. Now check whether your doors still open, whether the top stair tread doesn’t become too shallow, and whether your thresholds and door stops allow it. Trimming doors is doable, altering a staircase is a whole other story.
2. Check the substrate. Screw down loose boards first, with screws, not nails. Level out big height differences. A floating floor on an uneven substrate will rock, and then you’ve got a new noise on your hands.
3. Lay the perimeter strips. All the way round against every wall, and around pipe penetrations, radiator pipes and the stairwell opening too. This strip has to run up above the new floor, and you only trim it once everything is finished. It’s the most skipped step and the most fatal.
4. Lay the resilient layer. Wood fibreboard, mineral wool in board form, or a rubber granulate mat. Butt joints tight, don’t stack it, don’t screw it down, don’t glue it to the substrate.
5. Lay the screed. Gypsum fibreboard in two layers, or ready-made floor elements with a rebate. Glue and screw in the rebate, with staggered joints. The screws only go through the screed, never into the joists.
6. Only now trim the perimeter strip. Flush with the screed.
7. Fit the skirting with a gap. Fix the skirting to the wall, not to the floor, and leave 2 to 3 millimetres clear of the floor. Seal that gap with a permanently flexible sealant. Fixed at both ends turns your skirting board into a sound bridge.
The real work is in the discipline: nowhere may the new floor touch the old structure or the wall, except through the resilient layer.
Step by step: a decoupled ceiling on resilient bars
Working from below, you’re building a mass-spring-mass system. The existing floor is the first mass, the resilient bar is the spring, the new plasterboard is the second mass, and you fill the cavity in between with wool.
1. Strip out the old ceiling. Work with a proper dust mask (P3), dust extraction and goggles. In a property built before 1994, asbestos-containing material can be lurking in boards or old linings. If you’re not sure, get it tested first and don’t start sawing into it yourself.
2. Fill the cavity at least 70 per cent with mineral wool or wood fibre. Fit it as a friction fit so it can’t slump.
3. Screw resilient bars at right angles to the joists against the underside of the joists, typically at 40 to 60 centimetre centres, following the manufacturer’s specification. Resilient bars are thin metal profiles that make contact at only one point and therefore pass vibration on poorly. They’re a lot more effective than timber battens, which transmit vibration perfectly happily.
4. Keep clear of the wall everywhere. The resilient bars and the plasterboard must not touch the wall. Leave a 5 to 10 millimetre gap all round and fill it later with flexible sealant. If your new ceiling touches the wall, you’ve built a flanking path and you lose a big chunk of the gain.
5. Two layers of plasterboard, joints staggered, is clearly better than one. Mass is your friend here. For the lower layer, use a heavier acoustic board if you like.
6. Screws go into the resilient bar only. Choose a screw length that makes hitting the joist behind it impossible. One screw that’s too long and you’ve bridged the spring.
7. Everything airtight. Every gap, every penetration, every recessed downlight is a leak path. Downlights, by the way, are the silent killer of any acoustic ceiling: they’re literally holes in your mass. Don’t use them, or choose acoustically enclosed fittings.
The flanking paths: where most jobs fall apart
You can decouple the floor perfectly and still hear the same thing. That’s the sound going round it. Work through this list.
- The joist ends in the wall. There’s rarely anything to be done here without major structural work. What you can do is build an independent lining wall in the adjoining room, which breaks the path into the living space.
- The skirting boards. Fixed to wall and floor is a rigid connection. Keep it clear of the floor and seal the gap.
- The staircase. A timber staircase hanging off the floor structure is an enormous sound bridge. Decoupling it with rubber layers at the fixing points helps, and carpet on the treads helps more still.
- Pipe penetrations. Heating pipes and wastes that pass tightly through the floor transmit vibration. Rubber grommets or a generous opening with flexible sealant sort that out.
- Radiator brackets. On a wall that stands on the joists: decouple with rubber washers.
- Doors and thresholds. A gap under the door lets airborne noise through unhindered. A drop-down seal or draught strip does more here than you’d think.
- The floor that carries on. If your new floor runs through into the hallway or another room without a break, the sound travels with it. Make a genuine break at door openings with a flexible joint.
The low-frequency trap
Now a subtlety you’ll find in almost no DIY article, and it decides whether the job feels like a success.
A floating floor is, in physics terms, a mass on a spring. A system like that has a natural frequency at which it positively likes to vibrate along. Above that frequency it damps beautifully, around it, it can even amplify the sound.
The heavier the mass and the softer the spring, the lower that natural frequency sits and the more you benefit from the damping. Choose a resilient layer that’s too thin or too hard under a light floor, and that natural frequency shifts upward, right into the range of thudding footsteps.
What that means for you in practice:
- A thin, hard underlay beneath laminate helps against sharp clicks, but it can leave the low thudding unchanged or make it worse.
- Always combine a soft resilient layer with enough mass on top. Soft plus heavy is the winning combination, hard plus light is the losing one.
- If the job’s finished and the high clicks have gone but you still hear “thud”, this is usually the cause. The answer is more mass above the resilient layer, not just a thicker resilient layer.
This is also why a timber joist floor is harder to quieten than concrete: with concrete the mass is already there, with timber you have to organise it yourself, inside a tight weight budget.
Does it creak too? That’s a different job
Creaking isn’t a soundproofing problem, it’s a mechanical one. Insulation won’t fix it. These will:
- Nails are the culprit. Timber moves, the nail works loose, board and nail shank rub against each other. Replace nails with screws, into the joist, not next to it. Screw from above through the board into the centre of the joist.
- Board against board. With tongue and groove, the boards rub against each other. A bit of talc or graphite powder in the joint often works surprisingly well.
- The joist in its bearing. If it creaks near the wall, there’s play at the bearing. A strip of felt or rubber between joist and bearing damps that.
- Loose battens or laths under the floor: screw them down, and where timber rubs on timber, slip a strip of felt in between.
Always do this before you lay a new floor over the top. Afterwards you can’t get to it.
Quick wins without any building work
Not every situation calls for a building site. These things cost little and genuinely help.
- A big, thick rug with underlay along the walking route upstairs. This is the cheapest effective measure against impact noise that exists, full stop.
- Felt glides under every chair and table leg. Scraping chair legs are often the number one complaint in dining rooms.
- A socks-or-slippers agreement. Sounds feeble, in practice makes more difference than an expensive underlay.
- Washing machine and tumble dryer on anti-vibration feet, and levelled properly. A machine on spin cycle on a timber floor is a subwoofer.
- A wall of cupboards against the shared wall, packed full of stuff. Mass plus absorption, for free.
- Carpet the stairs, even if it’s only the bottom half.
- Seal the gaps under doors with a draught strip or a drop-down seal.
Common mistakes
- Wool between the joists and nothing else, then being surprised that footsteps sound just as loud.
- Forgetting the perimeter strip, or trimming it too early, which creates a direct connection between screed and wall.
- Screwing through the resilient layer into the joist. One screw, whole job ruined.
- Fixing skirting to floor and wall at the same time.
- A wet screed on old joists with no structural check.
- Putting recessed downlights into a freshly built acoustic ceiling.
- Relying on a certificate measured on concrete when you’ve got a timber floor.
- Leaving gaps and penetrations open. Sound behaves like water: it finds the hole.
- Not doing the height sums beforehand, then discovering halfway through that the door won’t open.
- Starting without checking the joists for rot, woodworm or deflection.
What does it cost?
| Item | Realistic range |
|---|---|
| Mineral wool or wood fibre for the cavity | 8 to 20 euros per m² in materials |
| Resilient layer under a floating floor | 6 to 20 euros per m² |
| Dry gypsum fibre screed | 25 to 55 euros per m² |
| Resilient bars plus two layers of plasterboard | 25 to 50 euros per m² in materials |
| Perimeter strips, sealant, screws, tape | 3 to 8 euros per m² |
| Complete floor soundproofing contracted out | 25 to 75 euros per m² including installation |
| Structural check by an engineer | 250 to 750 euros |
| Acoustic measurement by a consultant | 400 to 1,200 euros |
Guide prices. For the contracted-out version: have the quote state explicitly which build-up will be used and what performance is being aimed for, and whether a measurement is included. “Soundproofed floor” with no specification is not an agreement.
Let’s be honest about payback: there isn’t any, this is comfort. You do get thermal insulation between the storeys thrown in, which counts if you don’t heat upstairs, and a demonstrably quieter house does better at sale time. But don’t talk yourself into a saving.
How do you know it worked?
Do the same little test before and after, and you’ve got something to compare.
The simple walking test: have someone upstairs walk a fixed route in socks and then in shoes, while you stand downstairs in the same spot. Record it on your phone. Do exactly the same after the job. You’ll hear the difference played back.
The bag test: drop a full bag of rice onto the floor from 30 centimetres up, always in the same place. This mimics the low thud that’s hardest to get rid of.
The proper measurement: an acoustic consultant measures to NEN 5077 with a tapping machine. That’s the only result that’s any use in a dispute with an owners’ association or in a legal argument. Costs more, but produces a report nobody can wave away.
Frequently asked questions
Does insulation between the floor joists help against footsteps?
Barely. Insulation between the joists mainly damps airborne noise such as voices, music and TV, by making the cavity between floor and ceiling less resonant. Footsteps are impact noise, and that travels through the timber from board to joist to ceiling and wall. To tackle that, you need mass and decoupling: a floating screed on top, or a decoupled ceiling on resilient bars underneath.
What’s the difference between walking noise and impact noise?
Walking noise is what you hear in the room you’re walking in, the hollow thud of your own floor. Impact noise is what the people a storey below hear. They call for different solutions: you tackle walking noise with a dense, low-air underlay or extra mass, and impact noise with decoupling and closing the flanking paths. An underlay with a 10 dB certificate has been tested for impact noise downwards and says nothing about your own walking noise.
Am I allowed to lay a hard floor in a flat?
That depends on your lease or deed and the house rules of the owners’ association. Many associations require the floor finish to improve impact sound insulation by at least Ico = +10 dB, sometimes +12 or +15 dB. Read those documents before you buy anything, and ask the supplier for a certificate that matches your substrate. If there’s a timber joist floor underneath, a certificate measured on concrete is no guarantee.
How much height does a floating screed cost me?
Reckon on 30 to 60 millimetres for the resilient layer plus the screed, and your floor finish comes on top of that. Measure beforehand whether your doors still open, whether the top stair tread stays acceptable and whether thresholds and door stops allow it. Trimming doors is half an hour’s work, altering a staircase is a project in itself.
Can a timber joist floor carry a floating screed?
A dry screed in gypsum fibreboard adds around 30 kilos per square metre, and a sound joist floor in a home can generally take that, within the usual design value of 1.75 kN/m² imposed load. A wet screed in anhydrite or sand-cement adds 85 to 105 kilos per square metre. That’s a different order of magnitude, and that’s one for a structural engineer to look at. If in doubt, also check the joist ends at the wall for rot.
What’s a sound bridge and why is it so bad?
A sound bridge is any rigid connection that bypasses the decoupling you carefully built in: a screw through the resilient layer into the joist, a skirting board touching both wall and floor, a screed running up against the masonry. Vibration takes the easiest route, and one stiff connection is enough to leak away most of your gain. With decoupling, the workmanship matters more than the material.
Does a carpet really help?
Yes, and it’s the cheapest measure there is. That +10 dB figure the owners’ associations use didn’t come out of nowhere: it was derived from what short-pile carpet delivered on average. A decent rug with underlay along the walking routes upstairs does more against footsteps than many an expensive underlay, without a single screw.
Are you planning to take the floor out, move pipework, or take on a whole storey? Then you want to know what the build-up will be, how much height you’ll lose and where everything goes before the first board comes up. In Koning van je Woning I show you step by step how to tackle floors, walls and finishes yourself, with the details that make the difference between “a bit better” and genuinely quiet.
Do yourself a favour. This weekend, put the rug down first and do the walking test with your phone. Then you’ll know straight away what a proper job would buy you, and whether it’s worth the effort to you.
Cheers, Fred Schouten, builder and DIYer to the core.
PS: that perimeter strip. Seriously. I once laid a beautiful floating floor and at one spot the screed ran up against the wall. That’s exactly where you heard everything. Two hours of chiselling to free it again. Do it right first time.