Custom Audio Designs Ltd 



Basic Soundproofing Help and Advice

Uprating Domestic Timber Floors

A standard tongue & grooved chipboard floor will give stop around 37dB of airborne noise reduction and let through around 80dB of impact noise. If you have 'gapped' square edged floorboards then you have very little soundproofing performance because the only layer of sealed mass will be the plasterboard ceiling below. The noise will NOT be blocked, in any way, by floorboards with gaps between them so the performance will be even worse than that described above.

The most basic thing to do is to lift the floorboard and add 100mm acoustic mineral wool in the cavity space. You should then seal up the gaps and cracks between the existing square edges floorboards and then add a sealed hardboard top layer. You ideally also need to add an additional sheet of 12.5mm plasterboard to the ceiling below. This will improve the airborne noise reduction from less than 37dB to around 43dB.

In most situations it is impractical to install additional plasterboard to the ceiling below so instead you should add 1 (preferably 2) layers of Tecsound Acoustic Membrane to the topfloor. This will significantly increase the floors mass as well as damping out the vibrations which will still try to get through. This will increase the airborne noise reduction up to about 45dB.

If impact AND airborne noise are the problems then you need something more resilient under the topfloor layer.

The simplest option would be to install acoustic carpet underlay beneath the carpet. This will improve impact noise by up to 15dB but will only marginally (if at all) increase the airborne noise performance. Alternatively you can lay Quietfloor Slabs directly beneath carpet to improve both the airborne AND impact noise even further.

If you are laying a wooden topfloor (with no carpet) you should consider using either IsoBase floor isolation OR lay our QuietFloor slabs beneath the proposed topfloor.

Both the previous options ideally require acoustic mineral wool in the joist space and the floor to be sealed airtight before proceeding.

It must be remembered that increasing the mass of a floor will inevitably increase its height in the room and that doors may need to be trimmed so that they still close. This can also make a stepped lip between rooms which may not be convenient.


To improve the floor performance with reduced height rise you should lift the floorboards and install wood plank inserts joists to bring the surface level flush with the top of the joists. This will give you a sealed base floor the same height as the top of the joists. From there you can add whatever products are necessary and save yourself about 10mm of height rise.

The thicker and denser the wood inserts, the better.

Your noise problem, limitations and budget will determine what product will be your ideal solution. If you are unsure please call us so we can help find the best solution.

Some examples are as follows:-

  • You can add acoustic membrane if airborne noise is the only problem.
  • You can add a decent carpet underlay if impact noise is just your problem and you are having a carpet finish.
  • You can add acoustic membrane and decent carpet underlay if airborne and impact noise is the problem.
  • For improved performance you can add quietfloor slabs if airborne and impact noise is the problem. These can be installed directly beneath carpet or wooden top flooring.
  • You can add isobase floor isolation if impact noise is the problem and you are installing a wooden top floor.

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