Knauf Rocksilk RS100 Acoustic Mineral Wool is a high-density 100kg/m³ rock mineral wool insulation slab used for acoustic, thermal and fire protection applications. It is suitable for use in walls, floors, ceilings, internal partitions, separating floors, fabrication work and specialist acoustic build-ups where a denser mineral wool slab is required.
This variable product is available in 50mm, 75mm and 100mm thicknesses, allowing you to choose the correct slab depth for your wall, floor or ceiling cavity.
Knauf Rocksilk RS100 is used to provide high-density mineral wool infill within building cavities and acoustic systems. It can help absorb sound energy inside wall, floor and ceiling voids, while also supporting thermal and fire performance.
It is commonly used where density and mechanical characteristics are important, including specialist fire protection, fabrication work, acoustic partitions, separating floors and higher-density insulation applications.
Rocksilk RS100 helps absorb sound energy within cavities. Empty cavities can resonate and allow sound to pass through more easily. Installing mineral wool inside the cavity helps reduce this resonance and supports the performance of the complete soundproofing system.
RS100 is not a standalone soundproofing barrier. It should be combined with suitable board mass, acoustic plasterboard, resilient bars, Genie Clips, MuteClips, acoustic membranes, acoustic sealant and correct perimeter detailing where required.
RS100 is denser than both RS45 and RS60. RS45 is a 45kg/m³ slab, RS60 is a 60kg/m³ slab, and RS100 is a 100kg/m³ slab.
A higher-density slab is not automatically the right choice for every acoustic cavity. The correct product depends on the system design, cavity depth, required density, fire requirement, mechanical requirement and project specification.
For many standard wall and ceiling cavities, RS45 or RS60 may be suitable. RS100 is typically selected where a denser, more specialist slab is required.
Knauf Rocksilk RS100 can be used in a range of acoustic and insulation applications, including:
Knauf Rocksilk RS100 is a high-density mineral wool slab that offers acoustic absorption, thermal insulation and Euroclass A1 non-combustible fire performance in one product.
The slabs are easy to cut and friction fit between framing members. The 1200mm x 600mm slab size makes them practical for common wall, floor, roof and ceiling applications.
Choose the thickness based on the depth of your cavity and the system specification. The slab should fit neatly without being heavily compressed.
For soundproofing projects, RS100 should normally be used with additional mass, decoupling and airtight sealing. Mineral wool alone will not fully soundproof a wall, floor or ceiling.
If you are unsure whether RS100 is the right density for your project, please contact our team before ordering. We can help advise on the most suitable acoustic build-up for your wall, floor or ceiling system.
Knauf Rocksilk RS100 Acoustic Mineral Wool is a high-density 100kg/m³ rock mineral wool slab used in acoustic, thermal and fire protection applications. It is suitable for internal walls, partitions, floors, ceilings, separating floors, light steel frame walls, timber frame walls and specialist fabrication work.
| Product Name | Knauf Rocksilk RS100 Acoustic Mineral Wool |
| Brand | Knauf Insulation |
| Product Type | High-density rock mineral wool insulation slab |
| Application | Acoustic, thermal and fire protection insulation |
| Material | Rock mineral wool |
| Density | 100kg/m³ |
| Thermal Conductivity | 0.034 W/mK |
| Reaction to Fire | Euroclass A1 non-combustible |
| Binder Technology | ECOSE® Technology |
| Slab Size | 1200mm x 600mm |
| Area Per Slab | 0.72m² |
| Available Thicknesses | 50mm, 75mm and 100mm |
| Facing | Unfaced slab, unless otherwise stated |
| Main Acoustic Function | Sound absorption within wall, ceiling and floor cavities |
| Standalone Soundproofing Product? | No — should be used as part of a complete acoustic system |
| Thickness | Slab Size | Slabs Per Pack | Pack Coverage | Declared R-Value |
|---|---|---|---|---|
| 50mm | 1200mm x 600mm | 6 slabs | 4.32m² | 1.45 m²K/W |
| 75mm | 1200mm x 600mm | 4 slabs | 2.88m² | 2.20 m²K/W |
| 100mm | 1200mm x 600mm | 3 slabs | 2.16m² | 2.90 m²K/W |
Knauf Rocksilk RS100 can be used in a range of applications, including:
Rocksilk RS100 is used to absorb sound inside cavities. It is normally installed between studs, joists or frame members before the plasterboard or acoustic board layers are fitted.
It helps reduce cavity resonance and supports the performance of the complete soundproofing system. It should be combined with appropriate mass, decoupling and airtight sealing for best acoustic results.
Knauf Rocksilk RS100 is an acoustic insulation slab, not a complete soundproofing system on its own.
The final acoustic result will depend on the full wall, floor or ceiling construction, including the existing structure, cavity depth, board mass, decoupling method, perimeter sealing, workmanship and flanking noise paths.
For Building Regulations, fire-rated or compliance-led projects, use the correct tested system specification and seek project-specific advice where required.
Store packs clean, dry and protected before installation. Do not leave mineral wool exposed to weather or standing water.
Wear suitable PPE when cutting and installing mineral wool, including gloves, long sleeves, eye protection and a dust mask. Cut slabs with a sharp insulation knife or suitable saw.
Knauf Rocksilk RS100 Acoustic Mineral Wool is installed within wall, floor and ceiling cavities to provide acoustic absorption, thermal insulation and fire protection support.
For acoustic projects, it should be installed neatly between studs, joists or framing members without gaps, heavy compression or rigid bridging.
Choose the correct thickness for your cavity depth and system specification. RS100 is a high-density slab, so make sure the chosen thickness is suitable for the available space and the intended build-up.
Check the installation area before fitting. The cavity should be clean, dry and free from loose debris, sharp fixings and obvious gaps.
For soundproofing systems, plan the complete build-up before installing the mineral wool. This may include acoustic plasterboard, resilient bars, Genie Clips, MuteClips, acoustic membranes and acoustic sealant.
Measure the distance between the studs, joists or frame members.
Take measurements at several points because older buildings and timber frames are not always perfectly even.
For a neat friction fit, the slab can usually be cut slightly wider than the cavity, but it should not be forced in so tightly that it becomes heavily compressed.
Place the Rocksilk RS100 slab on a stable cutting surface.
Use a sharp insulation knife or suitable saw to cut the slab to the required size. Cut cleanly and avoid tearing the edges.
Where possible, cut pieces so they fit tightly around studs, joists, noggins and services without leaving open gaps.
Push the slab gently into the cavity so it sits flush with the framing.
The insulation should fill the cavity evenly. Avoid leaving air gaps, voids or loose edges.
Do not heavily compress the mineral wool. Heavy compression can reduce its ability to absorb sound within the cavity and may make the board layers harder to install correctly.
Cut neatly around pipes, cables, sockets, noggins and other obstructions.
Do not leave large holes around services. Small gaps can reduce the overall acoustic performance of the system.
Where services pass through the wall, ceiling or floor, use suitable acoustic sealant or approved fire/acoustic detailing as required by the project.
For wall installations, fit the Rocksilk RS100 between timber or metal studs before installing the plasterboard or acoustic board layers.
Make sure the slabs are supported by the studs and sit flat within the cavity.
For acoustic walls, the mineral wool should normally be combined with suitable board mass and airtight perimeter sealing.
For ceiling soundproofing systems, fit the Rocksilk RS100 between the ceiling joists.
If the ceiling is open from below, friction fit the slabs between the joists or use suitable retention netting where required.
Make sure the mineral wool does not drop, sag or leave open gaps before the ceiling board layers are installed.
For timber floor voids, fit the Rocksilk RS100 between the floor joists to reduce cavity resonance.
Where needed, support the insulation with netting, wire or suitable support battens so it remains in position.
Do not use RS100 as a load-bearing floating floor resilient layer unless it has been specifically specified for that purpose. It is normally used within the cavity rather than as a compressed layer beneath a floating deck.
If the mineral wool is being used in a decoupled system, make sure it does not create rigid bridges between isolated layers.
The insulation should sit within the cavity and should not be packed so tightly that it forces isolated boards, clips, channels or frames out of position.
Once the Rocksilk RS100 is fitted, install the specified plasterboard, acoustic plasterboard or soundproofing board layers.
Follow the board manufacturer’s fixing guidance. In clip and channel systems, only fix boards into the channel and avoid fixing through into the structure behind.
For high-performance acoustic systems, stagger board joints between layers and use acoustic sealant around perimeters.
After the board layers are installed, seal perimeter gaps, service penetrations and small openings with suitable acoustic sealant.
Pay attention to:
Good airtightness is essential because sound can pass through small gaps.
Knauf Rocksilk RS100 Acoustic Mineral Wool helps absorb sound within cavities, but it does not block sound by itself.
The final performance depends on the complete wall, floor or ceiling build-up, including existing structure, board mass, decoupling method, acoustic sealing, workmanship and flanking paths.
If you are unsure which thickness or density is right for your project, please contact our team before installation. We can help advise on the most suitable acoustic build-up for your wall, ceiling or floor.
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