40mm Knauf Rocksilk RS45 Mineral Wool Slab

The 40mm Rocksilk RS45 from Knauf is a mineral wool insulation slab with a standard density of 45kg/m3. This non-combustible building material delivers outstanding fire performance, achieving Euroclass A1 classification—the top rating for non-combustible products.

Sized at 1200mm x 600mm, the Knauf RS45 insulation slab provides excellent thermal and acoustic performance for both new builds and refurbishment work.

These slabs are odour-free, non-hygroscopic, and naturally rot-proof. They're manufactured without CFCs or HCFCs and resist fungal, mould, and bacterial growth.

With an unfaced finish and certified thermal conductivity of 0.035W/mK, the 40mm RS45 delivers reliable thermal efficiency. The 45kg/m3 density makes it ideal for internal partitions, timber and metal stud work, and installation between timber rafters and floor joists.

The material excels at sound absorption, offering significant sound reduction properties. Installation is straightforward—simply cut and shape using a large-bladed knife or saw.

Product specification

• Brand: Knauf®
• Model: 40mm Rocksilk RS45
• Thickness: 40mm
• Length: 1200mm
• Width: 600mm
• Dimensions: 1,200mm x 600mm x 40mm
• Board Coverage: 0.72m2
• Pack Coverage: 8.64m2
• Pack Quantity: 12
• R-Value: 1.10m2K/W
• Thermal Conductivity: 0.035W/mK
• Density: 45kg/m3
• Colour: Brown
• Material: Rock mineral wool
• Fire Classification: Euroclass A1
• Vapour Resistivity: 5.00MNs/g.m.
• Fire Reaction: Non-combustible
• Building Regulations: Class '0'
• Finish: Unfaced
• Shipping method: Articulated Vehicle ǀ Courier
• Applications: Floor ǀ Wall ǀ Roof ǀ Partitions
• Foil faced: No
• ECOSE Technology: Yes
• ETA Notification: Yes
• Features: Thermal and Acoustic Insulation Performance
• Manufacturer: Knauf Rocksilk®

Made to order Facings

For a factory applied foil or tissue facing please request a quotation using the website form or by calling our agents. We do offer single side or double side foil/tissue facings.

Applications

These 40mm Rocksilk building slabs suit a wide range of uses. Install them between rafters in pitched roof systems, use them for intermediate floors and floor separation, fit them into internal stud partitions, or incorporate them into light steel frame construction. OEM manufacturers also utilise these slabs for creating thermal, acoustic, and fire-rated products. Available across a density range from 45kg/m3 to 140kg/m3, Rocksilk® building slabs deliver non-combustible performance for diverse applications.

Benefits

• One slab type works across multiple applications.
• Factory-applied foil or tissue facing options are available, expanding the range of suitable uses.
• Crafted from mineral wool, it provides superior sound absorption and noise reduction versus standard alternatives.
• Made from rock mineral wool with a melting point above 1000°C, delivering extended fire resistance compared to many other common insulants.

Info

Browse our full Knauf Insulation range and refine by thickness or coverage using the left-hand filters. Need advice on product suitability for your project or a bulk discount quote? Get in touch by phone on +4402038839057, email sales@insulationbee, or use Live Chat for the best UK Knauf loft insulation prices.