Magnesium oxide flat boards are made from a mixture of undefined ratio between MgO and MgCl2, reinforced with fiberglass mesh or cloth at either one or both faces. Mainly produced in China on manually or semi-manually low technology pruduction lines, they generally have the following sizes:
Magnesium oxide boards are widely used at low priced projects in developing countries due to their non-combustibility, low price, water resistance in intermittent wet areas. However, their inherent weaknesses include instable quality, poor mechanical strengths against static and impact load. In addition, in areas of permanent high moisture, a phenomenon called "sweating" often occurs, leaving stains on the finished wall and ceiling surfaces already coated with paint. In brief, magnesium oxide flat boards should only be used for low cost laid-in exposed grid ceiling systems that do not require long lasting high aesthetic level for surface finishing. When used as lining boards for screwed-up concealed grid ceilings and drywall partitions, it is very difficult to stop cracks at board joints, which frequently occur due to high expansion / shrinkage of the boards under the temperature and moisture fluctuation of the working environment.
