MgO Fire Board Versus Portland Cement Board
MgO boards are harder than drywall and are somewhat like the Portland cement board used in bathtub enclosures. MagMatrix Sulfate MgO Board is using the chloride-free sulfate formula and with testing by Intertek for the market which totally solves the corrosive problems on metals & steels frame when making the application. MgO is ‘worked’ in a manner like a combination of drywall and cement boards. It can be scored and snapped, although it is stronger than drywall and requires a bit more effort.
It can be cut with a power saw, drilled-through and fastened like other similar boards. As when sawing Portland cement boards, dust is created and thus precautions against inhalation need to be taken, but the dust itself is basically inert. It’s an easy-to-install product. Like any sheathing board, MgO board can absorb water but its performance is unaffected. Thus it can be used indoors and outdoors, and in damp locations, such as showers. Like Portland cement-based sidings, if MgO is used outdoors in an exposed location, it needs some form of coating, such as paint. MgO can be used structurally–as in bracing for walls–and also semi-structurally, such as an underlayment for flooring.
MgO boards are not completely homogeneous (they are like Portland cement boards that have a glass scrim in the face), but do not have a separate facing like drywall or glass matt-faced gypsum board. Hence delaminating is not an issue–for practical purposes it is a solid material.
MgO board is more flexible than Portland cement boards and less flexible than drywall. Thin sheets of MgO can be bent or warped to follow gentle curves. MgO is not as brittle as Portland cement boards, but “edge distance” (closeness of fasteners to the edge of a sheet) is an issue in using certain types of fasteners. For instance, it can be nailed, but the hammering of the surface by the tool when setting the nail can damage the surface, although the nail itself does not. It’s basically like drywall or cement boards, in terms of ease-of-installation.
MgO board is quite stable. When subjected to temperature changes, it does not expand or contract much, nor does it absorb much water, or swell, when wet. When installed like drywall as a facing for partitions or as fire walls, the joints between MgO boards are treated much like drywall, using joint compound and a light mesh scrim.
Suitable for Structural Sheathing MgO board is quite strong and has good flexural and tensile strength, making it suitable as a structural sheathing, such as would occur with stucco, or as a substrate for EIFS. It also has high impact resistance, making it good for damage-prone applications, such as hurricane areas, or when used with a simple surface coating in areas where the wall might get beat up. No doubt you are aware of the current level of concern about mold and mildew. MgO board does not support the growth of mold or mildew at all, as there is nothing in MgO board that is attractive to mold and mildew. Similarly, termites and other insects have no interest in it, as it is inedible.
The fire properties of MgO boards are similar to gypsum boards. It is technically non-combustible in terms of the building codes and has a “zero” flame spread and smoke developed rating. MgO board does not burn at all, and can often be substituted thickness-for-thickness for Type X drywall in fire rated wall assemblies. Some proprietary MgO systems have been tested in two-, three- and four-hour UL-rated assemblies.
Being a stone-like material, MgO board has limited thermal insulation value, like gypsum and Portland cement products. The surface of MgO board, although it can be made very smooth, is slightly absorptive, making it possible to paint and bond-to the surface. This makes it good for applications like ceramic tiles, and thin, synthetic stuccos, adhesives, and EIFS.
In terms of weight, MgO board, on a thickness-to-thickness basis, is about 20 percent heavier than drywall, depending on the density of the MgO board. It is about 20 percent lighter than Portland cement sheathing boards.
The cost of MgO boards is similar to cement boards, on a per-thickness basis. The variation in the price of MgO is mostly based on transportation costs, and varies with the geographic location of the end-user, as shipping is a major cost component. Labor costs would also be similar to Portland cement boards.