MgO Board and Cement Board: Two Strong Competitors
When drywall isn't suitable — think wet areas, exterior applications, or tile substrates — cement board has long been the go-to alternative. But MgO board has emerged as a strong competitor that matches or exceeds cement board in nearly every performance category, while also being easier to handle and cut. So which should you choose?
How They're Made
Cement board (brands like HardieBacker, Durock, and Wonderboard) is made from Portland cement reinforced with aggregates and fiberglass mesh. It's heavy, rigid, and well-proven in wet area applications.
MgO board is made from magnesium oxide and magnesium chloride (or sulfate), reinforced with fiberglass mesh and lightweight fillers. It cures at room temperature rather than requiring kiln processing.
Head-to-Head Comparison
| Property | MgO Board | Cement Board |
|---|---|---|
| Weight (per sheet) | Lighter — easier to handle | Heavier — harder to maneuver alone |
| Cutting method | Score-and-snap or carbide blade | Requires carbide blade; very dusty |
| Edge fragility | Moderate — less brittle than cement board | High — edges chip and crumble easily |
| Fire resistance | Class A non-combustible | Non-combustible but less documented |
| Moisture resistance | Excellent | Excellent (but can allow water through) |
| Mold resistance | Excellent — fully inorganic | Good — inorganic, but biofilm can form on surface |
| Flexibility | Higher — can curve slightly for radius walls | Rigid — will crack if flexed |
| Thermal insulation | Slightly better due to perlite content | Minimal thermal value |
| Cost | Comparable to or slightly more than cement board | Well-established pricing; widely available |
| Availability | Growing but still limited in some markets | Widely available at all building supply stores |
Workability: A Real-World Advantage for MgO
Anyone who has worked with cement board knows the challenges: it's extremely heavy, the edges crumble when cut, and cutting it with a power saw creates a cloud of fine silica dust that requires serious respiratory protection. MgO board can be scored and snapped like drywall for straight cuts, dramatically speeding up installation and reducing the health risks associated with silica dust exposure.
For professional tilers and tile setters working on complex layouts with many cuts, this workability advantage translates directly into faster installation and less fatigue.
Moisture Behavior: A Nuanced Difference
Both materials are moisture resistant, but they handle water differently. Cement board can absorb water and allow it to pass through to the framing behind — it is water-durable but not truly waterproof. MgO board is similarly not a waterproofing layer on its own, but its inorganic matrix resists moisture penetration more effectively. In both cases, a waterproofing membrane is recommended for direct-water applications like shower enclosures.
One Caveat: MgO Board Quality Varies
It's worth noting that MgO board quality is less standardized globally than cement board. Early-generation MgO boards used magnesium chloride binders that could absorb atmospheric moisture and weep chloride salts — a phenomenon called "sweating" or hygroscopic behavior. Higher-quality modern MgO boards use magnesium sulfate or optimized chloride formulations that have largely eliminated this issue. Always purchase from reputable suppliers who can provide third-party test documentation.
Which Should You Choose?
- Choose MgO board when: ease of cutting, weight reduction, fire ratings, or flexibility are priorities — or when working on large-scale projects where installer fatigue and speed matter.
- Choose cement board when: material availability is critical, the project team is already familiar with cement board, or sourcing vetted MgO products is difficult in your market.
Both materials are sound choices for tile backing and wet area applications. MgO board edges ahead in workability and fire performance; cement board retains the advantage of universal availability and a long track record in the field.