Rockwool Sound Insulation | Sound Insulation

Welcome to our Rockwool Sound Insulation category at insulation4less. Navigating through the numerous options of sound insulation can be daunting, but when you choose Rockwool, you’re selecting products that combine superb acoustic performance with excellent fire resistance and thermal capabilities. Let's delve deeper into the notable products within this category.

Choosing ROCKWOOL for sound insulation

Good sound control comes from the whole wall or floor build-up, not from one slab in isolation. Stone wool works inside the cavity as an absorber. Its open, non-directional fibre structure helps absorb sound energy and damp vibration, while plasterboard layers, resilient bars, separated frames and airtight perimeter sealing deal with other sound paths. That is why a thicker or denser slab should not be treated as a stand-alone dB rating for a finished wall.

For this collection, the practical choice is between RWA45, FLEXI and RW3. RWA45 is the broad general-purpose option. FLEXI is useful where a reliable friction fit between timber or metal members is the priority. RW3 is a denser RW slab used where the specification calls for its acoustic, thermal and fire properties. All three are stone wool products and are Euroclass A1 for reaction to fire.

Which one do I need?

What thickness of ROCKWOOL is best for soundproofing?

The right thickness is the thickness that fills the intended cavity without being forced into a smaller space and that matches the tested or designed construction. More millimetres do not create a universal soundproofing result. A 50mm stud cavity normally needs a product intended to fit that cavity; a deeper floor or wall can accept a deeper slab where the system permits it. Do not quote a slab thickness as a guaranteed airborne or impact sound reduction on its own.

ROCKWOOL’s own Sound Insulation Slab literature illustrates the point. In one new-build separating timber floor build-up, 100mm Sound Slab is used between 200 x 50mm joists together with an acoustic resilient layer, OSB, resilient bars and multiple plasterboard layers. The stated performance belongs to that complete tested construction, not to the 100mm slab by itself.

Rockwool RWA45

Practical Uses

The Rockwool RWA45 insulation slabs are renowned for their thermal, acoustic, and fire-resistant properties. These slabs are versatile in use, being suitable for multiple applications including floors, walls, and roofs, across both domestic and commercial buildings.

Selection Guidance

When selecting RWA45 for your project, consider the specific thermal or acoustic requirements of the space. The varied size options allow you to choose a thickness that aligns with your insulation needs, always ensuring compliance with building regulations. Ideal for projects where a balance of acoustic and thermal performance is required alongside stringent fire protection.

Rockwool Flexi-Slab

Practical Uses

The Rockwool Flexi-Slab, renowned for its flexibility and precise fit, provides an exceptional solution where insulation must adapt to varied spacings in walls, ceilings, and floors. This product encompasses a unique dual-density insulation design, ensuring secure positioning and eliminating gaps that can compromise performance.

Selection Guidance

Opt for Flexi-Slab when you need a flexible and robust insulation solution that can adeptly conform to irregular surfaces and spaces. It’s especially apt for timber-framed walls or any application where you need to insulate between variable width beams or studs, offering a tight, energy-efficient fit wherever it’s installed.

Rockwool RW3 Acoustic, Thermal, and Fire Performance Insulation Slabs

Practical Uses

The Rockwool RW3 series offers holistic performance in acoustic, thermal, and fire insulation, making them versatile across an array of applications including acoustic partitions, suspended ceilings, and general building applications.

Selection Guidance

The RW3 series is the go-to choice when you require top-tier acoustic insulation alongside premium thermal and fire resistance, especially in spaces prone to high noise levels or where privacy is paramount. Choose this series for enhanced sound absorption and to meet fire safety standards without compromising on thermal performance.

Installation points that matter for acoustic performance

Cut slabs accurately around pipes, cables and other services so the cavity is filled without avoidable gaps. Keep the insulation within the cavity and do not rely on compression to solve an incorrect thickness choice. At plasterboard faces, acoustic performance also depends on the board layers, frame arrangement, resilient components where specified, and careful sealing at the perimeter and penetrations.

For separating constructions, follow the project specification or a tested system rather than mixing components from different examples. Approved Document E sets sound requirements for dwellings in England, but a mineral wool slab by itself is not evidence that a finished wall or floor complies. Where compliance is required, check the complete build-up and any testing requirements before ordering.

Frequently asked questions

Is ROCKWOOL good for soundproofing?

ROCKWOOL stone wool is well suited to acoustic insulation because its fibre structure absorbs sound energy inside wall, floor and ceiling cavities. It should be treated as one component of a sound-control system. Plasterboard mass, framing, resilient layers, junction details and airtight sealing also influence the finished construction’s airborne and impact sound performance.

Is 50mm ROCKWOOL enough for soundproofing?

50mm ROCKWOOL can be appropriate where the designed cavity and construction call for a 50mm slab. It should not be presented as a universal soundproofing thickness. The finished result depends on the complete wall or floor, including board layers, framing, decoupling and sealing, so follow the relevant tested or specified build-up.

Is 100mm ROCKWOOL better than 50mm for sound insulation?

A 100mm slab fills a deeper cavity and can provide more absorption within a construction, but thickness alone does not give a guaranteed dB improvement. ROCKWOOL system examples combine insulation with boards, resilient layers and structural elements. Choose 100mm where the cavity and tested or designed build-up require it, rather than compressing it into 50mm.

What is the difference between RWA45 and RW3?

RWA45 and RW3 are both ROCKWOOL stone wool slabs for acoustic, thermal and fire applications. ROCKWOOL lists RWA45 at a nominal density of 45kg/m³ with λ 0.035 W/mK, while RW3 is 60kg/m³ with λ 0.034 W/mK. Select by the project specification, cavity and required system performance.

What is the difference between RWA45 and FLEXI?

RWA45 is a general-purpose semi-rigid RW slab, while FLEXI is designed with a flexible edge to support a close friction fit between the insulation and its supporting framework. FLEXI is particularly useful between timber or metal members. Both provide acoustic and thermal benefits and achieve Euroclass A1 reaction to fire.

Can ROCKWOOL sound insulation be used in stud walls?

ROCKWOOL RWA45, FLEXI and RW3 can all be used in appropriate framed wall applications. The slab should fit the cavity closely and be cut around services without leaving avoidable gaps. For a separating or performance-rated wall, use the exact product, thickness, boards, studs and fixing arrangement required by the specified system.

Can ROCKWOOL be used between floor joists?

ROCKWOOL stone wool slabs can be installed between timber floor joists as part of an acoustic floor and ceiling construction. The insulation helps absorb sound within the void, while impact and airborne performance also depends on the deck, ceiling layers, resilient treatment and junction details. Follow the relevant floor build-up rather than judging the slab alone.

Does ROCKWOOL stop impact noise?

Stone wool in a floor cavity can contribute to the overall acoustic performance, but impact noise is strongly affected by the floor surface and structural transmission path. Effective impact-noise systems often use a resilient floor layer or other isolation detail as well as cavity insulation. Use a tested floor build-up where a defined performance level is required.

Does ROCKWOOL sound insulation also provide thermal insulation?

Yes. The products in this collection have declared thermal conductivity values as well as acoustic uses. RWA45 is 0.035 W/mK, RW3 is 0.034 W/mK, and FLEXI is 0.038 W/mK at 50–120mm and 0.035 W/mK at 140mm and above. Thermal performance still depends on thickness and the full build-up.

Can I compress ROCKWOOL into a smaller cavity?

Choose a thickness that suits the available cavity rather than forcing a substantially thicker slab into a shallower space. Acoustic insulation should fit closely without avoidable gaps, but compression is not a substitute for correct product selection. Where a tested wall or floor system is being followed, keep to the stated product thickness and construction details.