4.5 out of 5 Stars on

Rockwool External Wall Dual Density Slab

(1 customer review)

From £20.75 Excl. VAT

  • Size of boards: 1200 x 600mm
  • Breathable
  • Euroclass A1 Non-combustible
  • Hard-wearing
  • This product is sold in individual packs
  • Coverage per pack varies – please see below for coverage

Rockwool External Wall Dual Density Slab

Rockwool External Wall Dual Density Slabs are a premium insulation board composed of mineral wool, which is a very similar material to fibreglass. While fibreglass is made up of thousands of glass fibres, Rockwool is made from molten volcanic rocks. The material is produced by heating the volcanic rock within a large furnace, then spinning it into fibrous strands and compressing it into boards. As a vapour-permeable insulation material, the boards are ideal for use with a breathable thin coat render such as EWI Pro’s Silicone Render. Rockwool is the insulation material of choice for architects and builders alike.

Another benefit of Rockwool Dual Density insulation boards is that they are completely non-combustible. The insulation boards have achieved a Euroclass rating of A1 for non-combustibility – this is the highest rating that an insulation material can achieve. With fire-safety being so topical and of such importance, the Rockwool insulation goes extra lengths to offer complete assurance against the threat of fire.

With the ability to withstand temperatures of up to 1,000ºC (1,800ºF), the Rockwool insulation helps to effectively contain and prevent the spread of fire. At the same time, the stone wool will not produce any toxic smoke or emissions. This makes Rockwool insulation the ideal product for areas of urban development, and for high-rise structures.

When you choose Rockwool External Wall Dual Density Slabs for your external wall insulation system, you also gain the added benefit of acoustic insulation. The open porous structure of the stone wool means that the boards are able to absorb and reduce the impact of sound, enabling homeowners to enjoy a comfortable, quiet internal environment. In highly populated areas or for homes and buildings that are within close proximity to road traffic, the benefits of this are unrivalled.

The Rockwool External Wall Dual Density Slab is specially crafted to be ideal for external wall insulation. The boards are called ‘dual density’ because they are made up of two different density layers of wool; a low density for the subsurface and high density for the exterior. The lower density will accommodate slight imperfections in the fabric of the building, and the higher density top layer is the ideal surface for the application of renders. Rockwool external wall insulation boards require metal pin mechanical fixings as well as a strong adhesive to tie them to the wall (a minimum of 7 fixings are required per m2).

Technical Specification

  • Composition: Mineral Wool
  • Thermal Conductivity: 0.036W/(m2K)
  • Density: 110kg/m³
  • Minimum Compressive Strength: 10 kPa
  • Reaction to Fire: Class A1 (non-combustible)
  • Size of boards: 1200 x 600mm
  • R-value: 1.39W/(m2K)
  • Density: 110kg/m3
  • Weight: 15.84kg
  • Weight/m2: 5.5kg


Use netting on scaffolding as well as a protective rainproof covering to reduce exposure to elements such as rain and excess sunlight.


Rockwool Mineral Wool insulation slabs should be installed in accordance with the manufacturer’s instructions – these include guidelines on design and other aspects of application. We recommend the boards are fixed to the substrate with mortar/adhesive and mechanical fixings to ensure maximum adhesion.

Because of the greater weight of Mineral Wool, we advise that you use the EWI-225 Premium Basecoat for the application rather than a standard adhesive, which is used on lighter insulating materials. Apply a light, watery based coat of the adhesive to your prepared surface initially. When it is dry, apply the basecoat, then sink in the Fibreglass Mesh.

Coverage Rates

Thickness of board (mm) Coverage per pack (m²)
50 2.88
70 2.16
90 1.44
100 0.72
110 0.72
120 0.72
150 0.72
200 0.72


Shelf life: please see the manufacturer’s date of expiry. Keep in a dry place, in the original undamaged packaging, avoid excess heat or UV light exposure.

Weight 139 kg

50mm, 70mm, 90mm, 100mm, 110mm, 120mm, 150mm, 200mm

1 review for Rockwool External Wall Dual Density Slab

  1. JohnnyBB27

    Used to convert shed into home office (with the 075 Silicone render). Great finish, and the office now warms up quickly and stays warm.

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