• Overview
  • Technical Data
  • Downloads


A1 non-combustible, MgO board

RCM Extremegreen MgO magnesium oxide board is a high density structurally reinforced magnesium oxide based sheathing consisting of a proprietary composition of magnesium oxide (MgO) and magnesium chloride (MgCl2) that is reinforced with multiple layers of glass fiber mesh. Magnesium oxide is a mineral based raw material.

The sheets are made in various lengths, widths and thicknesses providing a huge range of building options.

As an A1 non-combustible sheathing board Extremegreen is an excellent choice for structural timber applications.


  • Fire rated to EN 13501-1 class A1
  • Water resistant
  • Environmentally friendly
  • Mould resistant
  • Contractor friendly
  • Gypsum and crystalline silica free
  • Easy to work with
  • Integrates with other RCM products

Standard Board Sizes

  • 2400 x 1200mm (6mm, 9mm and 12mm)
  • 2397 x 1198mm (9mm)
  • 2697 x 1198mm (9mm)
  • Other board sizes are available.


RCM Extremegreen can be cut, drilled and nailed using conventional hand tools; offering many of the properties of timber.

For cutting the product in any volume, we recommend the use of a hand held circular saw with a 60+ tooth finish blade. Alternatively, RCM offer a complete fabrication service, please contact our technical department for details.

Key applications

  • Sheathing board
  • Ceilings and roofing
  • Internal wall lining
  • Tile backer board
  • Buildings above 18m
  • Flooring and sub-flooring

Suitable for the following construction types

  • Timber Frame
  • Modular / Offsite

Technical Data

  • Contact us for more information - 0800 612 4662


01 . 5
Add Sample to Basket

Add to Sample Basket

Thank you for requesting samples – make sure to click ‘add to basket’ to complete your order.