Rockwool External Wall Dual Density Slab


4.11 out of 5 based on 9 customer ratings
(9 customer reviews)
  • 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 its 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 1.44
110 1.44
120 1.44
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

9 reviews for Rockwool External Wall Dual Density Slab

4.11 out of 5
Write a review

  1. Chris Burling

    Would recommend using this Rockwool on the outside walls. Was much denser than I was expecting so took basecoat well and the sound reduction it has made when in our house is incredible (live on busy street). Will have to wait for the winter to see how how it works in terms of thermal performance.

  2. Jacek Buczek

    Best product ever to use for external wall insulation

  3. JR

    Wouldn’t use anything else going to be perfect for the green homes grant !!

  4. Sophie

    I am so confused, I am not sure whether to get External Wall Insulation on my home 🙁

    • Alana

      Don’t worry! It can seem like a daunting and complex process but I can assure you that its easier than it sounds and our expert team can guide you through it, just contact us at [email protected] and we can help you with any questions you may have 🙂 I hope this helps!

  5. Bart

    So I was literally googling weight loss diet pills but somehow ended up here, but I’m not complaining! Great article, makes me want to look into External Wall Insulation myself.

    • Alana

      That’s bizarre XD If you do decide to go ahead with External Wall Insulation then don’t hesitate to contact us at [email protected] 🙂

  6. Mustafa

    Wow there are a load of comments here XD Last time I was on this page it was empty, glad you guys are writing these useful articles, it helps so much!

    • Alana

      There sure is XD we love to help people learn about Silicone Render and External Wall Insulation on our blogs 🙂

  7. Rajibal

    Hi there, not sure how I ended up on this page but am looking for some advice on Silicone Render?

    • Alana

      Thank you for your comment, please contact us at [email protected] or give us a call 🙂

  8. Bob Sallow

    Another great article guys, keep it up!

    • Alana

      Thank you! 🙂

  9. Sandy M

    Great product, I’m interested in getting External Wall Insulation on my home at the moment, just in the research phase so this article has been really helpful 🙂

    • Alana

      That’s great to hear! If you have any further queries don’t hesitate to contact us 🙂

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