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Rockwool RW3 100mm

£28.00 (Excluding VAT)

£33.60 (Including VAT)

Why Choose Rockwool RW3 100mm

Performance: will vary due to featuring in acoustic systems.*

Dimensions: 1200mm x 600mm x 100mm.

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®.

There is currently a shortage on Rockwool RW3, RWA45, Knauf RS60 and RS45 within the UK, please do contact do office before orders so we can indicate stock availability

Specialist Acoustic Mineral Wool for Part E Building Regulations Compliance

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 100mm (4 per bale - 2.88m2)
  • Other thicknesses include; 75mm, 50mm and 30mm
  • 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

  • 100mm
  • 75mm 
  • 50mm 
  • 30mm
  • 4 Slabs (2.88m2) 
  • 6 Slabs (4.32m2) 
  • 8 Slabs (5.72m2) 
  • 15 Slabs (10.8m2)

Why is this Rockwool 60kg, and what does the 60kg mean?

60kg is the density of the product when measured in cubic meters and not the weight of a single slab or bale of acoustic mineral wool - it is a reasonably lightweight sound insulation product that is easy to cut and easy to lay, use gloves and eye protection and keep the area ventilated during and after installation.

Where is Rockwool Acoustic Mineral 100mm best used?

100mm is the thickest slab of acoustic mineral wool available and is best used as stud wall insulation, between flooring joists or flooring frameworks with our MuteCradle options to prevent cavities from resonating, leaving them untreated will lead to any remaining sound passing through into these areas. You will also want to avoid using a thicker size than the air gap provided and aim to have at least a 10mm air gap on either side. Using a 100mm thickness in a 50mm cavity, for example, will lead to compression of the acoustic mineral wool and a direct path of sound to travel through which will result in degrading the acoustic performance.

Can Acoustic Mineral Wool be used to soundproof a room against noise?

You will want to install acoustic mineral wool in timber and metal frameworks, in our suspended ceiling or wall systems such as in our MuteClip System and flooring cavities between joists or with our MuteCradle options it can be used to treat all these cavities to reduce sound from bouncing around inside them and resonating. But, it is essential to note that this is a lightweight, fibrous material and this means that sound will pass through it - so it is not effective in reducing airborne nor impact noise issues as a standalone solution.

Can I use Rockwool Acoustic Mineral Wool to treat noise reverberation?

Acoustic Mineral Wool is fibrous and will release fibres into the room when exposed, and it should only be placed in cavities and generally is not recommended to use as an exposed sound absorption material for this reason.

We offer a comprehensive range of sound absorption range that can are available in an almost unlimited range of possibilities across a broad range of colours.

Are there any allergens or toxic elements found in Rockwool?

As a fibrous material, it can lead to slight irritation of the skin, those with sensitive skin may find a slight redness appear while handling it - the use of gloves and protective eyewear is recommended.

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.

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