140mm Rockwool Flexi Acoustic Sound Insulation Slab (2.88m2/Pack)

Product Overview

Stone wool insulation slab, measuring 140mm in thickness and cut to 1200 × 600mm, for use in partitions and floors.

With a patented flexible edge, it securely friction fits within framed constructions, reducing the need for excessive cutting and limiting waste on site.

In a single solution, it provides reliable acoustic absorption, effective thermal insulation with a conductivity of 0.038 W/mK, and the highest level of fire safety (A1 non-combustible).

Its semi-rigid form allows straightforward handling and installation, while maintaining a close fit to minimise gaps that could compromise performance.

At 140mm thick, the deepest slab in the Flexi range, it offers the highest levels of acoustic and thermal performance. 

The additional depth enables superior airborne sound reduction between rooms and floors, while further improving energy efficiency by reducing heat loss through the building envelope.

Features & Benefits

• FLEXI Edge® along one side: Ensures snug, continuous fit in timber or metal frames, reducing gaps and air leakage.
• Non-combustible stone wool (Euroclass A1): Contributes to fire-safe wall, floor, and roof constructions.
• Effective acoustic absorber: Reduces airborne sound transmission through stud partitions and intermediate floors.
• Thermal conductivity 0.035 W/mK: Supports energy-efficient envelopes within framed build-ups.
• Will not slump, even if studs shrink: Maintains full fill and consistent performance over time.
• Easy to handle and cut: Speeds installation and fitting around services with minimal waste.
• Slab size 1200 x 600mm: Standard board dimensions suit common stud spacings.
• 140mm thickness: Thickest slab in range - for deep frames where maximum performance is required.
  
  

Applications

• Timber or metal stud partitions: Improves airborne sound reduction and thermal performance.
• Party walls in timber frame: Used within twin-frame/independent stud solutions to address acoustic and thermal bypass.
• Suspended timber floors: Laid between joists; supports sound control and U-value targets when used with appropriate membranes.
• Pitched roofs and warm/hybrid frames: Between rafters or as part of hybrid build-ups to enhance thermal continuity.
  
  

Installation Guidance

• Friction-fit installation: Flexible edge holds slabs tightly in place, reducing the need for mechanical fixings.
• Cut to fit with a sharp knife: Ensures minimal waste and precise fitting around services.
• Avoid gaps or voids: Maintains full thermal, acoustic, and fire resistance performance.
  
  

Compliance & Performance

• Reaction to fire classification A1 (EN13501-1): Fully non-combustible for high fire safety.
• Thermal conductivity 0.035 W/mK: Provides consistent insulation in framed constructions.
• High acoustic absorption: Tested to provide broadband sound reduction in lightweight partitions.