How to Soundproof a Floor

How to Soundproof a Floor

Tired of having to listen to noise created by your neighbours from below?

Do you live in an apartment where sound travels between adjoining dwellings, and it is affecting your quality of life?

Or maybe you just need to reduce sound transmitted between rooms in your own home?

It’s time to soundproof your floors to prevent these nuisance noises once and for all.

By adding appropriate acoustic insulation to the floors and structures, you will be in a better position to control sound transmission of numerous kinds from space to space.

In the majority of cases, installing soundproofing materials to floors is a very effective option, as long as you choose the appropriate application based on correct diagnosis.

Ultimately, the solution will depend on the type of noise you are contending with, the structure of the property and the type of floors installed.

So, it’s important that you make a well informed choice before pressing ahead.

The following considerations and tips should be able to guide you through this process:

Initial Considerations

Some of the most important factors you will need to consider include:

  • What is the original source ignition (ie what is causing the noise) and from where it originates
  • Type of noise that you are dealing with – structural airborne or impact or perhaps both
  • Noise levels – frequencies and dB ratings – the higher the volume, the more extensive and robust your soundproofing solution will need to be.
  • Pathways of movement, ie how is the noise travelling from its starting point to the area of concern, could it also be through the structural / support wall construction causing flanking transmission
  • Type of floor construction/make-up of the floor – is it timber joisted flooring or a solid floor such as concrete slab
  • Tolerances and depths available to accomodate a satisfactory acoustic solution must be considered.

Locate the Source of the Noise

Before pressing ahead with a soundproofing project, it is important to carefully consider the source of the noise that’s bothering you.

Many people unwittingly proceed with soundproofing projects without giving this much thought, assuming that as long as they fit some form of soundproofing material directly to the subfloor, that it is going to do the job.

But in reality, blocking unwanted sounds isn’t quite so straightforward.

Firstly, you need to locate the exact source of the noise.

And in reality, that could be multiple places.

You also need to ascertain whether the noise is being heard throughout the house, or only in a particular room.

Also, are you trying to stop noise from entering your property from above, below or possibly both?

If the noise is coming from above, traveling downwards, it is going to require a different method than noise that is coming from below and travelling upwards into the home.

Both upward movement and downward movement can result in additional flanking transmissions through support walls and the building’s own structure.

Do not overlook this possibility and investigate thoroughly, as this can be a much less obvious pathway for transmission, but can in some cases be as big a problem as the floor structure itself.

Floorboards & Skirting Boards

Floor Construction

The floor’s construction is of critical importance when it comes to choosing the best soundproofing materials and methods.

There are invariably two main types of floor constructions:

Timber Joisted Floors

This includes floorboards on timber joists.

In this case, you will generally find that there’s a substantial space between the joists, and sometimes below the joists, but this will be dictated by a number of factors.

Invariably services such as cables and pipework will be found within these cavities. They may or may not have any form of insulation installed.

If access to this cavity below the subfloor is possible, investigate if the cavities are filled with anything.

If and where possible any cavities between joists should be filled/partly filled with a dense open cell material which will offer an absorption of sound-waves/energy from above.

More importantly the insulation will prevent each cavity from being an open resonant cavity and acting like a mini cave, which invariably leads to a heightened level of regeneration and resonance of sound waves within the space, resulting in amplified levels hitting the uppermost side of the existing ceiling structure below.

In older buildings, the existing floorboards could be nailed down to exposed timber, whereas in more modern constructions, ply or chipboard is commonly used as a subfloor.

In both cases, impact sounds as well as structural airborne sounds tend to be a significant problem.

Concrete Floors

Concrete floors, or solid floors, generally come as a minimum of a solid 150mm/6” slab in most properties.

As concrete floors have a higher level of mass, they will block airborne sounds well enough in most cases.

However impact noise can still be a problem.

Dog Laying on Concrete Floor

Type of Noise – Impact or Airborne

Once you’ve identified the source of the noise, you will then need to consider whether it is impact noise or airborne noise.

Sometimes it can be a combination of both, which poses greater challenges, but you will need to investigate and consider carefully what is the main type of noise that is proving to be most bothersome to you.

In such a way you will be able to choose the best soundproofing material and method to address it correctly and effectively.

The two main types of noise are:

  • Airborne sound – such as sound from appliances, TVs, radios, and chatter, these become structural airborne when the noise contacts a structure such as a floor / wall / ceiling.
  • Impact sound – such as footfall, footsteps and anything that contact a surface area.

Level of Noise

The volume of the noise is your next consideration.

Needless to say, the higher volume or louder the sound, the more robust the soundproofing solution needs to be.

Low level noises, such as muffled speaking, the humming of appliances, or low-end TV audio sounds (airborne) will require less soundproofing than for example louder noises, such as impact noise from banging and crashing on surfaces.

It is important to discuss your specific noise problems with a professional acoustic consultant who specialises in soundproofing.

This is because the type and volume of noise, as well as where it originates, all affect the type of soundproofing material and method that will be the most effective.

Grey Carpet Pile

Soundproofing a Floor

Impact noise is generally trickier to handle than airborne noise.

Such noises involve the ‘thud’ of the impact of whatever hits the floor, and this is generally accompanied by vibration which arises from the impact and travels through the building’s own substrate or rigidity.

As outlined above, the structural cavities where possible can have an open cell insulation installed to assist with absorption and prevent resonance.

This may be a simple solution where access is available and if not, it is certainly harder to remedy but should be seen as a vital step in any strategy to prevent an amplification of sound from above.

Arresting impact noise before it enters the building’s own substrate, such as the rigid floorboard, ply, joist or slab, as much as possible is important.

The type of acoustic strategy will usually be determined by the depth or tolerances available to house an insulation material – usually the thinner the better to prevent issues with finishing levels, head height, uneven thresholds for example.

The severity of the source ignition and the amount of resulting vibration through the type of build in question will also need consideration.

A good starting point for isolating impact and airborne sound through a floor may be as simple as installing a good quality carpet and carpet underlay.

Not to say that this a soundproofing option, but it will certainly offer a level of mitigation against both footfall and airborne sound waves.

Problems tend to be more prolific when a carpet finish is old and worn.

Even worse when the existing carpet is to be replaced with a hard wood floor finish.

These types of floor are increasingly popular with the ease of cleaning and allergy prevention.

The most recommended types of floor soundproofing for impact / airborne sounds include:

Carpet & Carpet Underlay

A standard and simple approach which a lot of people overlook.

A good quality carpet and underlay will offer a very good initial step to lessening impact sound directly onto a hard floor and also absorb internal acoustics within the room reducing airborne/structural airborne transmission through the floor.

Acoustic Isolation Membranes

This is a relatively simple step to install onto the subfloor before a carpet underlay/carpet or under a laminate wooden floor for example and are very thin.

Acoustic isolation membranes, such as Acoustiblok’s 3mm or 6mm Sound Isolation membranes, are easy to install as they can be cut and fit into place with minimum depth.

Acoustiblok offers the best sound attenuation millimetre for millimetre than any other membrane solution.

Thin finishing ply or tile backer boards can be laid over the insulation, where required, to further increase a mass layer.

Floating Floors

Floating floor solutions are invariably thicker and bulkier methods, but are effective as they basically add decoupling layers of mass and density to the existing floor.

However this will be an isolated structure, thus the sound transmission will be reduced considerably.

Floating floors are exactly that. They sit on top of the original subfloor without mechanical fixing and comprise a layer which is bonded to the underside.

Open Cell Absorbent Core

When it comes to airborne noise, the best way to reduce the transmission of sound is via acoustic open cell absorbent insulation within cavity spaces for example.

There are various kinds of acoustic insulation materials, all of which adhere to the principle of having a high density to absorb sound.

Acoustic Underlays/Mats

Acoustic underlays can also be a popular option where an increased depth of assembly is available.

These could be considered a hybrid solution with a layered combination of dense rubber sandwiching acoustic foam in between, so as to achieve a dense mass decoupled by an absorbent core.

These can work well against most types of sounds, including both airborne and impact noise, depending on the severity of the task in hand, and can be incorporated into a floor with other principles to further increase effect.

Thin finishing ply or tile backer boards may be laid over the insulation to further increase a mass layer and prevent movement.

Acoustic Isolation Pads or Cradle/Batten Raised Flooring Systems

Where a much increased lift to the floor can be tolerated, raised flooring systems comprising either a roll out material with centred isolation pads or alternatively cradles / towers with a timber battening system can be installed.

These types of systems offer a much higher acoustic performance than most other solutions and are used within conversions and new builds to level floors.

These may be a much deeper solution but offer a decoupling through the isolation pads or cradles and framing system, an absorbent core in the cavities between the framing offers absorption and can also accommodate services with a finish of dense mass ply sheet and boarding materials.

Additional acoustic membranes can then be added on top of these systems for further increased performance.

Soundproofing Timber Floors

Timber floors can be soundproofed in different ways, however the most effective options include:

  • Install acoustic insulation membranes, such as Acoustiblok’s 3mm or 6mm isolation materials, which uniquely converts sound energy and offers the best sound attenuation millimetre for millimetre than any other sound isolation material.
  • Open cell cavity insulation within cavities and service voids.
  • Installing acoustic underlays / mats made from materials such as rubber, which is densely bonded together so as to be dense and effective to absorb sounds.
  • Floating floor systems comprising multiple layers of differing materials.
  • Raised flooring systems where space, tolerance and increased depths can be tolerated.

The concept is to absorb the impact sound immediately, and prevent it from transmitting into the floor structure, leading to the ceiling below.

First and foremost, establish if there is adequate cavity insulation between the timber floor joists.

A floor system where cavities have no insulation have the ability to become resonant spaces, potentially leading to a regeneration and amplification of the original source.

Therefore, where possible and cavities are accessible, it is absolutely the first principle to add sufficient absorbent open cell material to joist space.

Not only will this assist in basic levels of absorption it will also assist in the prevention of any increased acoustic levels.

Acoustic floor insulation is high density, making it very effective against airborne sound transmission.

This however will do little against the flanking transmission through the structure of the joists themselves.

This is invariably the biggest problem for any acoustic floor treatment.

Soundproofing Concrete or Screed Floors

Concrete floors already have a high level of mass, and so they are better able to reduce sound transmission than timber floors.

However, this is mainly the case with airborne sounds.

With impact sounds, the noise will generally still be able to transmit through the concrete as it can use the concrete’s own rigidity to move from one side to the other.

So you may wish to consider either:

  • Install acoustic insulation membranes, such as Acoustiblok’s 3mm or 6mm isolation materials, which uniquely converts sound energy and offers the best sound attenuation millimetre for millimetre than any other sound isolation material.
  • Installing acoustic underlays/mats made from materials such as rubber, which is densely bonded together so as to be dense and effective to absorb sounds.
  • Floating floor systems comprising multiple layers of differing materials.
  • Raised flooring systems where space, tolerance and increased depths can be tolerated.

Conclusion

The floor soundproofing options that we discussed above all have their respective pros and cons.

However, major importance should be given to their effectiveness considering your particular flooring structure, the space/depths available and the type and level of noise that you’re dealing with.

It is always best to seek assistance from a professional soundproofing specialist who will be able to evaluate your floors, their structure and the most suitable material.

Care will also be taken to ascertain the types and levels of noise that are to be dealt with.

Thanks to such a professional’s experience, the best soundproofing method and material can be selected.

In most cases there will be a mixture of both high dense mass material which will work to reduce impact noises, combined with the blocking of airborne noises.

Stopping sound from entering your property is not always easy to diagnose.

Sound travels quickly and manages to make its way into the structure quite easily.

It is after all a form of energy, and quite simply, an invisible invader which is difficult to predict and control.

However, with soundproofing materials and methods that are most suitable for your particular case, you should be able to significantly reduce sound transmission, and make your home far more peaceful and quiet than before.

Disclaimer

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