240mm Rockwool EWI External Wall Dual Density Slab

240mm Rockwool EWI External Wall Dual Density Insulation Slab delivers premium thermal performance for external wall insulation systems with established third-party certification.

Manufactured using Rockwool's patented Dual Density technology, these slabs feature a robust high-density outer layer paired with a flexible lower-density core. This innovative construction provides an excellent surface for render and fixture installation whilst accommodating substrate variations and imperfections.

When installed with tight butt joints, the slabs interlock to create a seamless thermal barrier, eliminating heat loss through gaps and cold bridges.

Specifying 240mm Rockwool DD insulation in an External Wall Insulation (EWI) system gives building owners and residents assurance of reliable long-term performance. Stone wool insulation delivers proven durability, with performance verified over 55+ years of real-world use.*

Product specification

• Brand: Rockwool®
• Model: 240mm EWI
• Thickness: 240mm
• Dimensions: 1,200mm x 600mm x 240mm
• Length: 1200mm
• Width: 600mm
• Board Coverage: 0.72m2
• Colour: Pale white
• Density: 110kg/m3
• Compressive strength: ≥ 10 kPa\t
• Tensile strength: ≥ 10 kPa
• R-Value: 1.39m2K/W
• Thermal Conductivity: 0.036W/mK
• Material: Molten volcanic rocks
• Profile: Square edge
• Temperature resistance: up to 1000ºC
• Fire Classification: A1 Non-combustible
• Shipping method: Articulated Vehicle ǀ Courier
• Applications: External Wall Insulation Systems
• Features: Thermal and Acoustic Insulation Slab
• Manufacturer: ROCKWOOL®

These 240mm external wall insulation boards showcase a distinctive dual-layer construction with two wool densities working in harmony. The lower-density inner layer flexes to accommodate minor building fabric irregularities, whilst the higher-density outer layer creates an ideal base for render application. Installation requires mechanical metal pin fixings alongside quality adhesive, with a minimum of 7 fixings per square metre recommended for secure attachment.

Application

Install Rockwool Mineral Wool insulation slabs following manufacturer guidance, including design specifications and installation procedures. For optimal adhesion, fix boards to the substrate using mortar or adhesive combined with mechanical fixings.

Given Mineral Wool's increased weight, we advise using the EWI-225 Premium Basecoat rather than standard adhesive designed for lighter materials. Apply a thin, diluted adhesive coat to the prepared surface first. After drying, apply the basecoat and set the Fibreglass Mesh into position.

Non-combustible

240mm Rockwool stone wool achieves the highest 'A1 – Non-combustible' rating under the European Reaction to Fire Classification System, guaranteeing it will not ignite or promote fire spread.

Durable

1. 240mm Rockwool DD slabs retain dimensional stability throughout the building's lifespan, resisting shrinkage and deterioration.
2. The dense outer surface supports secure basecoat application and prevents fastener over-driving.
3. Demonstrates excellent resistance to wind and rain exposure during the installation phase.
4. Proven and reliable: 240mm Rockwool has been integral to EWI systems throughout Europe for over 40 years.

Breathable

• 240mm Rockwool stone wool's breathable open-cell structure allows water vapour transmission, whilst its water-repellent fibres prevent water penetration.
• Provides vapour resistance equivalent to still air.

Thermal performance

Tightly butt-jointed slabs enable fibre interlocking, preventing heat losses through gaps in the insulation layer.

Acoustic performance

• EWI systems using 240mm Rockwool slabs increase building envelope mass, reducing sound and vibration transmission.
• The fibrous material contributes to sound absorption, with testing showing improvements up to 8 dB in weighted sound reduction, Rw (depending on substrate conditions).

Dual Density Slabs for External Walls

• Purpose-engineered for external wall insulation systems, Dual Density Slabs deliver a stone wool insulation solution.
• Manufactured using ROCKWOOL's proprietary 'dual density' process, these slabs incorporate a higher-density top layer relative to the remainder of the product. This creates a durable surface for render and fixture installation, with a flexible underside that accommodates substrate variations.
• For ease of installation, the top layer is clearly marked 'THIS SIDE UP', making the outer surface immediately identifiable.

More Information on 240mm Rockwool External Wall DD Slab

• Manufacturer Link: Rockwool DD
• 240mm Rockwool External Wall DD Slab is a premium-performance product with diverse application possibilities.
• Browse our full Rockwool Insulation range and refine by thickness or coverage using the filters on the left. For project-specific advice or bulk quotations, contact us on +4402038839057, email sales@insulationbee, or use Live Chat for the best UK Rockwool Insulation prices.