The Rockwool Flexi 90mm acoustic insulation slab is a high-performance stone wool board engineered for both acoustic and thermal control in framed constructions. With a thickness of 90 mm and standard slab size of 1200 mm × 600 mm, this pallet covers approximately 86.4 m² — tailored for larger scale installations, refurbishments or trade-focused projects.

Built with a thermal conductivity (λ) around 0.038 W/m·K, it delivers solid thermal resistance while also offering excellent acoustic performance thanks to the semi-rigid stone wool and the patented FLEXI Edge® that ensures a friction-fit between studwork, reducing gaps and improving build integrity. 
Fire safety is rock-solid: classified as Euroclass A1 (non-combustible) under BS EN 13501-1, it’s suited for demanding installations where fire and acoustic performance matter.

Installation is straightforward: the size fits typical board layouts, the FLEXI edge means fewer voids and better fitment, and the stone wool material maintains its shape (won’t slump or degrade) even if timber fames shrink over time. The product works for internal partitions, separating floors, ceilings, timber or metal stud walls — whether in new build or refurbishment.

In short, for projects where acoustic separation, thermal insulation and fire-safety are all on the spec sheet, the Rockwool Flexi 90 mm slab offers a premium solution built for trade professionals and serious installs.

Key Features

• Thickness: 90 mm — deeper cavity build-up for enhanced acoustic and thermal effect

• Panel size: 1200 mm × 600 mm (standard board dimension)

• Coverage: ~ 86.4 m² per pallet — efficient for large batch work

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

• Fire classification: Euroclass A1 (non-combustible) — top safety rating

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

• Patented FLEXI Edge® design for tight fit in framed systems, minimising gaps and wastage

• Suitable for: Internal partitions, separating floors/ceilings, metal/timber stud walls, large scale refurbishments

• Installation ease: Semi-rigid boards; easier to handle, cut and fit; less install waste; long-term performance