Main finishing options for Magnesium Oxide boards

May 2, 2016

Another question came in yesterday about the finishing of Magnesium Oxide Boards in case of exterior walling.

The most common exterior surface finishes are: Paint, Plaster and Tiles.

Before you start applying the finishing material:

When the MgO boards are fitted, the boards should not be exposed to the weather for a long period of time. Both heavy rains or high dryness will have their negative effects on shrinkage or expansion of the boards. These will cause cracks later when the finishing material is applied.
The MgO boards should also be clean and dry before starting finishing.
Small damages to the MgO boards should be removed or repaired.


Paint can be applied easily to the MgO boards. For exterior use, the boards should be primed with 1 or 2 coats of Plaster/Masonry Primer before coating with exterior quality paint. The primer works here as a sealant and water repellent that protects the ‘open’ structure of Magnesium Oxide Board.


Cement plaster can be applied to the surface of the MgO boards. All joints between the Boards must be meshed with Fibre Mesh (preferably 4mm x 4mm) or wire scrim prior to applying the cement plaster coat.
After plastering, a sealant primer should protect the Plaster.


Tiles may also be applied to the surface of the MgO boards. In this case it is recommended to roughen up the surface of the Board and put a suitable bonding agent (glue) on it before tiling. The amount of Glue has to be affluent.

When the tiles are applied for walls higher than 10 feet, these tiles should not be bigger than 1,3 Square Feet and thicker than 12mm.