The Rockwool Flexi Slab 50mm (1200 mm × 400 mm board size, pack covering approx. 5.76 m²) is a premium multi-purpose stone wool insulation solution designed for acoustic, thermal and fire performance in framed constructions. The slimmer board width (400 mm) combined with 50mm thickness makes it ideal for tighter cavities while still delivering strong performance.

Thanks to the patented FLEXI Edge® along one side, each slab pulls tight into timber or metal studwork with fewer gaps, reducing waste and improving fit. The product has a thermal conductivity of 0.038 W/m·K for the 50 mm thickness. It also boasts a Euroclass A1 non-combustible fire-rating, giving confidence in safety and regulatory compliance.

Installation is straightforward: the 1200mm length matches standard board layouts and the 400mm width aligns with many partition stud centres, making this slab well suited for walls, ceilings or floors where space is limited. The slab’s stone wool makeup provides excellent sound absorption and thermal retention, helping reduce airborne noise transfer as well as heat loss — perfect for refurbishments, flats, commercial interiors or any space where tidy build is important. The form-factor ensures faster install, less waste, and fewer compromises on performance. The slab is water-repellent, vapour‐permeable, and dimensionally stable — no sagging or long-term degradation when installed correctly.

Whether you’re upgrading a partition wall to meet acoustic specs, improving thermal insulation in a retrofit, or specifying premium insulation for a commercial interior, the Rockwool Flexi 50 mm slab (1200×400mm) delivers a smart balance of depth, fit-factor and performance. Ideal for trade professionals and ecommerce listings alike.

Key Features

• Thickness: 50 mm — for moderate cavity depths while retaining strong performance

• Board size: 1200 mm (L) × 400 mm (W) — tailored for tighter stud or joist spacing

• Pack coverage: ~5.76 m² (12 slabs per pack)

• Thermal conductivity (λD): ~0.038 W/m·K at 50mm thickness

• Fire rating: Euroclass A1 (non-combustible)

• Material: Stone wool (rock mineral wool) — water-repellent, vapour-permeable and dimensionally stable

• Patented FLEXI Edge® for improved fit between frames and fewer installation voids

• Excellent acoustic absorption and thermal resistance — suitable for walls, floors, ceilings, refurbished builds or new construction

• Easy to handle, cut and install, reducing waste and improving on-site efficiency