Rockwool Acoustic Mineral Wool RW3 25mm 60kg per m3

£54.95 (Excluding VAT)
£65.94 (Including VAT)

  • Performance: will vary due to featuring in acoustic systems.*
  • Dimensions: 1200mm x 600mm x 25mm.
  • Weight: 20kg
  • For: homes and workplaces.
  • Compliance: Compliant with Part E Building Regulations (England, Wales, Northern Ireland and the Republic of Ireland).*
  • Installation: will vary depending on which system it features.
  • Where: for all cavities found between floor joists, stud frame walls and ceilings.

Universally recognised throughout the world of soundproofing, commonly used as part of an acoustic system, or combined with additional acoustic materials such as our MuteClip®.


Rockwool PROROX SL930 Acoustic Mineral Wool (RW3) (60kg per m3) is high-density acoustic mineral wool that is used to treat the 'open spaces', or cavities, between flooring joists, stud-frame walls and ceilings. It is an open-fibrous material that when sound comes in to contact with, turns that sound energy into heat, essentially reducing the sound. Although, it is not used as a standalone and should always be used as part of a system where these open spaces exist. Acoustic Mineral Wool helps to prevent Flanking Transmission through the open cavities, and the sound amplifying. Any acoustic system fitted without it will not achieve its full acoustic performance and may fall short of expectations.

Acoustic Mineral Wool has a greater density than thermal wool comparisons which is evident in their slab appearance, the reduction in acoustic insulation for this material in the form of an NRC (Noise Reduction Coefficient) which differs for each thickness, what this essentially means is that it is an absorptive material as opposed to a dense, heavy soundproofing product. You will find all acoustic systems that Acoustic Mineral Wool is featured in, which there is most, by selecting the 'Systems' tab above.


  • Essential for all soundproofing systems with joists or stud-frames.
  • To be used in cavities to provide optimum soundproofing performance for all systems
  • Slab dimensions 1200mm x 600mm x 25mm (16 per bale - 11.52m2)
  • Other thicknesses include; 100mm, 75mm and 50mm
  • Euroclass A1 fire rating
  • Always leave an air gap to ensure full performance a minimum of 10mm
  • A 3-5 day lead time can be expected with Rockwool, please call ahead for availability



Rockwool RW3 Pack Quantities

4 Slabs (2.88m2)6 Slabs (4.32m2)8 Slabs (5.76m2)16 Slabs (11.52m2)
Length1200 mm
Width600 mm
Height400 mm

The world of soundproofing and general construction presents an uncertain journey for those arriving fresh to the subject, there maybe terminology or use of acoustic testing figures that could appear confusing, and even if you are at a professional level, it is good to brush up to make sure you are making the right choice. We want to help you come to the right decision, so whether this is through the use of our guides or talking to a member of our team - we are here to help!

How to Soundproof a Wall or Ceiling


A combination of the following will always result in a much improved acoustic performance.

  • Mass: the addition of more substantial materials to reduce sound energy, for example, added layers combined with soundproof Plasterboard.
  • Separation: breaking contact with the surface or surfaces through the use of acoustic isolation clips or stud framing.
  • Damping: the reduction of vibration through the use of flexible, damping materials such as Tecsound.


To create a soundproofing system that can reduce an extensive range of sounds and noises, you will need to combine all of the properties above. By separating the mass from the structure and suspending it away, you are breaking contact with the construction and creating an air gap, in this air gap must feature Acoustic Mineral Wool, as it is essential for reducing Flanking Transmission, and reducing any sound making it into the cavity. Low-frequency noises and vibration are not just created in areas with amplified music or machinery, but can originate from televisions attached to the wall, or the low-tone of a male voice and even closing a door - these noises often travel greater distances than you'd think, and will also on occasion, lead to Flanking Transmission. We recognise the subjective nature of sound and how we react to each one, and that is why we offer so many variances in our systems. We understand that it is not always possible to incorporate significant losses of space with say, the introduction of a stud frame, so we provide different variances to suit what performance you need, your budget and thickness.

Learn more about what you need, and how to approach soundproofing floors walls and ceilings below.


Ready to see what options you have available? Select our 'Systems' tab and on any system to learn more about each of their acoustic performances, overall system thickness and in what scenarios you can apply them to. You can then add all featured components to the cart in a press of a button!

Whatever the scenario, come and speak to our team on 01937 588 226.

  • Although acoustic insulation used here is not toxic or hazardous, when installing it does release small dust particles, so do use gloves, goggles or face mask.
  • Measure the depth of the cavity first, or if you know the stud depth you are using, make sure that you choose a depth of Acoustic Mineral Wool that allows for a 10mm air gap on either side.
  • The reason you leave this air gap is to avoid compressing the fibrous properties between the two partitions you are soundproofing, for example, do not use a 100mm depth in a 50mm gap.
  • Acoustic Mineral Wool is easy to cut with large scissors, or we found a bread knife to be a great tool here.
  • Cut the slab a little larger than the stud or joist gap to friction hold, or use a form of wiring to hold it in place.

This product is part of the following systems:

60kg is not the weight of the product as it comes, but the density of the product which is measured in cubic meters - it is a reasonably lightweight sound insulation material which is easy to cut and easy to fit.

The 25mm thickness is best used to help patch in small cavities and with use with our direct to brick, block or brick constructions, using a thicker size than the air gap provided. For example, using a 100mm thickness in a 50mm cavity will lead to compression of the acoustic mineral wool and creating a direct path for sound to travel through, this degrades the performance of any sound proofing system.

You will want to install Acoustic Mineral Wool in conjunction with dense soundproofing materials, and it is essential to note that as a lightweight, fibrous material, the sound will pass through it and that its prime function is to reduce sound from reflecting around the empty spacing of cavities and not to reduce noise transfer between rooms.

Acoustic Mineral Wool is a fibrous material, and this means that fibres can be released into the air when exposed - which is why it is usually in a cavity or covered, it is not recommended to use as exposed panelling.

We offer a vast range of sound absorption materials we tailor to your creative imagination with a variety of colours, as well as stock items in a range of designs and colours.

We have found that a bread knife usually makes for an excellent cutting tool if this is unavailable - a large pair of scissors will also work well.

There are no toxic elements found in Rockwool, but there are fibrous elements that can give a slight irritation to the skin, those with sensitive skin experience a little itching, so we recommend the use of gloves and protective eye-wear. This will be the case for all mineral wool insulation of spun-rock fibres.

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