Magnesium Oxide Board
This information reflects our best understanding of product composition in 2023.
Magnesium oxide (MgO) boards are cement fiberboards that may be used as an alternative to gypsum board for sheathing, subfloors, underlayment, and partitions. The boards are commonly composed of magnesium oxysulfate cement, a lightweight filler...
Magnesium oxide (MgO) boards are cement fiberboards that may be used as an alternative to gypsum board for sheathing, subfloors, underlayment, and partitions. The boards are commonly composed of magnesium oxysulfate cement, a lightweight filler such as perlite, wood fiber, and a fiberglass scrim. Magnesium oxychloride cement, or Sorel cement, is an alternative binder to magnesium oxysulfate cement though it is less commonly used and therefore outside the scope of this research. Magnesium chloride may still be present in small quantities in some magnesium oxysulfate products. A possible reason that magnesium oxysulfate cement is more commonly used is that the chloride content of the boards, when in contact with moisture, may result in moisture damage or "weeping boards". Various binders can be used in alkali-resistant fiberglass scrim. It is not clear what specific binder is common for scrim used in MgO boards. See the All Contents for other possible binders.