The Rockwool flexi slab 100mm Acoustic Insulation (1200 × 400 mm, covers ~2.88 m² per pack) is a premium stone-wool solution designed for serious acoustic, thermal and fire performance when space allows. With its generous 100 mm thickness and narrower board width of 400 mm, this slab fits snugly into tighter stud frames or specialist layouts where a standard 600 mm width may not suit.

Manufactured with the patented FLEXI Edge®, this slab ensures a secure friction-fit between timber or metal studs — helping eliminate gaps that compromise acoustic or thermal integrity. The product achieves a fire rating of Euroclass A1 (non-combustible), making it compliant and safe for use in demanding builds. The declared thermal conductivity is approximately 0.038 W/m·K, delivering strong insulation value alongside acoustic benefits.

From an acoustic standpoint, the added mass and depth of 100 mm helps reduce airborne sound and improves separation between rooms, floors or ceilings — ideal for apartments, offices or refurbishment projects where noise control matters. From a thermal side, the depth also boosts U-value improvement and helps retain heat in framed structures.

Installation is straightforward: cut the panels to fit, slot the FLEXI Edge® side against the frame, ensure snug fit with no voids or gaps, and line with plasterboard or acoustic board based on your build spec. Because the slab is stone-wool, it is water-repellent, dimensionally stable and resistant to sagging — meaning longer-term performance and less maintenance worry.

Whether you’re laying acoustic partitions, isolating between floors, upgrading ceilings, or working on refurbishments with limited width but ample depth, the Rockwool Flexi 100 mm slab makes a value choice — strong brand, spec-friendly, installer-approved.

Key Features

• Thickness: 100 mm — deep build-up for enhanced acoustic & thermal performance

• Dimensions: 1200 mm (L) × 400 mm (W) board size

• Pack coverage: ~ 2.88 m² (typically pack of 6 slabs)

• Thermal conductivity: ~ 0.038 W/m·K (λD)

• Fire classification: Euroclass A1 (non-combustible)

• Material: Stone wool (rock mineral wool) — durable, moisture resistant, dimensionally stable

• Patented FLEXI Edge® for tight fit and minimal wastage

• Acoustic & thermal combined performance — ideal for partitions, ceilings, floors

• Narrower width (400mm) suits specialist frames or less standard builds

• Easy installation: cut, fit, minimise gaps, maintain long-term performance