Rockwool Acoustic Insulation

Rockwool stone wool slabs for sound and thermal insulation – RWA45 acoustic slab and Rockwool Flexi – at trade prices, delivered to England and Wales in 2–3 working days.

RWA45 or Flexi?

  • Rockwool RWA45 acoustic slab, 1200 × 600mm in 50mm, 75mm and 100mm. A denser slab (45kg/m³) for partitions, separating floors, ceilings and walls where sound reduction matters. λ 0.035 W/mK.
  • Rockwool Flexi, 1200 × 600mm in 100mm and 140mm. A flexible-edged slab that friction-fits between timber studs, joists and rafters – mainly for thermal insulation in timber-frame walls, floors and roofs. λ 0.038 W/mK for 50–120mm, 0.035 W/mK for 140mm and above.

Stone wool is non-combustible (Euroclass A1), which is why it is often specified around party walls and floors. For acoustic performance, the whole build-up matters: stud width, board type (e.g. soundboard plasterboard), resilient bar and sealing all count. For lighter glass wool acoustic roll see glass mineral wool insulation, and use our drywall partition calculator to price a full wall.

Delivery: prices are ex VAT. We deliver to England and Wales in 2–3 working days – free on orders over £500 ex VAT, £50 below that, with a £400 minimum order.

Both slabs are stone wool rated Euroclass A1 (non-combustible), so Rockwool is a common choice where you want fire resistant insulation as well as sound insulation. For fire stopping at cavities and service penetrations, use a tested fire barrier or fire sealant system.

5 products

Rockwool slabs: buying guide

Rockwool stone wool slabs are dense, rigid enough to friction-fit, and non-combustible (Euroclass A1). We stock two: RWA45 acoustic slab and Rockwool Flexi.

RWA45 or Flexi?

  • RWA45 (1200 × 600mm, 50, 75 and 100mm, 45kg/m³, λ 0.035 W/mK) is the denser slab for partitions, separating floors, ceilings and walls where sound matters.
  • Flexi (1200 × 600mm, 100 and 140mm; λ 0.038 W/mK for 50–120mm and 0.035 W/mK for 140mm and above, per Rockwool’s datasheet) has a flexible edge that springs into place between timber studs, joists and rafters, so it’s mainly used for thermal insulation in timber frames, floors and roofs.

Getting good sound insulation

The slab is only one part of an acoustic wall or floor. Stud width, board type (for example soundboard plasterboard), resilient bar and sealing gaps with acoustic sealant all make a difference. Our guide to acoustic insulation explains the basics.

How many packs?

Each pack shows its coverage in the product name (for example 2.88m² for 100mm RWA45). The insulation calculator works out packs with a waste allowance, and the drywall partition calculator prices a complete stud wall.

Delivery and minimum order: prices are shown ex VAT. We deliver to England and Wales, usually in 2–3 working days. There’s a £400 ex VAT minimum order, delivery is £50 ex VAT on orders under £500 ex VAT and free over £500 ex VAT. Need a price for a large or mixed load? Call 03330 908479.

Frequently asked questions

Is RWA45 good for soundproofing a stud wall?

RWA45 is a dense acoustic slab designed for partitions and separating floors. The result depends on the whole wall build-up, including board type, stud width and sealing, so follow a tested system where performance is specified.

Can Rockwool Flexi be used in a loft or roof?

Flexi is designed to friction-fit between timber studs, joists and rafters, so it’s commonly used in pitched roofs and timber floors. Check ventilation and vapour control requirements for your roof.

Is Rockwool fire resistant?

Stone wool is non-combustible (Euroclass A1). Fire resistance of a wall or floor depends on the complete tested system.

How many slabs are in a pack?

Pack coverage is shown in the product name, for example 2.88m², 4.32m² or 6.48m² depending on thickness. Divide your area by the pack coverage and add waste, or use our insulation calculator.

Is there a minimum order and how much is delivery?

There’s a £400 ex VAT minimum order on insulation and building materials. Delivery to England and Wales is £50 ex VAT on orders under £500 ex VAT and free over £500 ex VAT, usually in 2–3 working days.

The Rockwool RWA45 Acoustic Insulation Slab is a multi-purpose solution built for thermal, acoustic, and fire insulation. Lightweight and easy to cut into shape, it is suitable for walls, floors, ceilings, and roofs. With dimensions of 1200mm x 600mm and a variety of thickness options, it can be tailored to fit your exact project specifications.

Features include:

  • Excellent thermal and acoustic performance
  • Non-combustible stone wool core for fire-resistant protection
  • Moisture-repellent properties to maintain structural integrity

Designed for ultimate flexibility and adaptability, the Rockwool Flexi Slab is perfect for applications in residential buildings where precision matters. Its unique dual-density edge ensures a snug fit, working exceptionally well in timber or steel frame constructions and cavity walls.

The versatile Rockwool Duo Slab delivers outstanding acoustic insulation alongside superior thermal resistance. Ideal for external walls, it helps reduce heat loss while mitigating sound transmission across various building applications.

For roof applications, Rollbatt Insulation Rolls provide enhanced thermal coverage and soundproofing. Lightweight and robust, it’s an excellent choice for loft spaces where energy-saving insulation can make the most significant difference.

Minimise sound transmission between rooms or through walls, creating quieter, more comfortable living spaces. Whether for home offices or multi-residential complexes, reducing noise pollution is crucial to maintaining productivity and peace.

The non-combustible nature of stone wool insulation provides peace of mind in the face of fire risks. Suitable for walls, roofs, and floors, Rockwool slabs help protect structures by preventing the spread of flames.

By retaining heat effectively, Rockwool insulation reduces the need for excessive heating or cooling systems. The result? Lower energy bills and a smaller carbon footprint.

Stone wool materials are durable and resistant to settling, sagging, and moisture intrusion. A one-time installation delivers performance that lasts decades, with minimal need for maintenance.

Whether closing cavities, insulating steel frames, or addressing soundproofing challenges, Rockwool products are designed to meet diverse construction needs with ease.