Fiber Cement Board Sheathing vs. MgO Board Sheathing
- JP Group MagMatrix Brand
- Jan 3
- 3 min read
Choosing between Magnesium Oxide (MgO) board and fiber cement board depends on your project’s location, climate, and budget. While MgO board excels in fire safety, moisture resistance, and eco-friendliness, fiber cement board offers superior long-term durability and impact strength.
Key Takeaways
MgO Board: Lightweight, easy to install (DIY-friendly), non-combustible, and highly moisture-resistant. Best for wet or fire-prone areas.
Fiber Cement Board Sheathing: Powerful, impact-resistant, and long-lasting (50+ years). Best for exterior durability.
Cost vs. Value: MgO has higher upfront costs but lower maintenance. Fiber cement is cheaper initially but heavier and requires more maintenance (painting/sealing).
Comparison at a Glance for the Fiber Cement Board Sheathing and MGO Board Sheathing
Feature | Fiber Cement Board | MgO Board |
Fire Resistance | Moderate to Good | Superior (A1 Non-combustible) |
Moisture Resistance | Water-resistant (needs sealing) | Waterproof (mold/mildew proof) |
Durability | High impact strength; 50+ year lifespan | Stable; 30+ year lifespan |
Installation | Heavy; requires special tools | Lightweight; score-and-snap |
Eco-Impact | Energy-intensive; hard to recycle | Low carbon; fully recyclable |
Best Use | Siding, tile backing, exteriors | Fire-rated walls, humid areas, interiors |
Composition
Fiber Cement Board
Materials: Cement (40-60%), silica (stability), cellulose/fiberglass (flexibility), and additives.
Properties: Dense and durable.
MgO Board
Materials: Magnesium oxide, perlite/vermiculite (lightweight fillers), fiberglass mesh, and bonding agents.
Properties: Mineral-based, naturally fire and water-resistant.
Durability and Performance
Impact Resistance & Longevity
Fiber Cement: Highly resistant to impact due to density. Can last over 50 years (often exceeding 100) with warranties typically spanning 30–50 years.
MgO Board: Dimensionally stable against wind and stress. As MagMatrix Brand BMSC 517 New Sulfate Mgo Board wall, roofing, and subfloor sheathing, their expected lifespan is 100+ years in average climates.
Fire Resistance
MgO Board: Rated A1 non-combustible (EN 13501-1) and ASTM E136 non-combustible grade, and withstands extreme heat (1-2 hours) without spreading fire.
Fiber Cement: Non-combustible and fire-resistant, though generally less effective than MgO under extreme direct flame.
Moisture & Mold
MgO Board: Does not absorb water, swell, or warp. The mineral composition naturally prevents mold and mildew growth.
Fiber Cement: Moisture-resistant but can absorb water if unsealed, potentially leading to cracks or mold. Requires proper sealing in coastal areas.
Health, Safety, and Environment
Sustainability
MgO Board: Low carbon footprint, made from natural minerals, and fully recyclable.
Fiber Cement: Energy-intensive production (mining/cement) and difficult to recycle; mostly ends up in landfills.
Health & Safety
MgO Board: Free from VOCs and formaldehyde. Safe for allergy sufferers.
Fiber Cement: Generally safe (asbestos-free), but cutting generates silica dust, requiring masks and ventilation.
Installation
Tools & Handling
MgO Board: Lightweight and easy to carry. Can be cut with a carbide-tipped scoring knife (low dust).
Fiber Cement: Heavy; often requires two people to lift. Cutting requires specialized shears or dust-reducing saws due to silica dust hazards.
Cost and Value
Material Cost: Fiber cement is generally cheaper ($5–$14/sq ft) compared to MgO ($8–$20/sq ft).
ROI: MgO offers better long-term value through faster installation (labor savings) and minimal maintenance. Fiber cement requires periodic repainting and resealing.
Applications
Fiber Cement: Exterior siding, tile backing, and areas requiring high impact resistance or longevity.
MgO Board: Commercial buildings (schools, hospitals), fire-rated partitions, basements, kitchens, and bathrooms.
Common Myths Debunked
Fiber Cement
Myth: It gets water-damaged easily. Fact: It resists water well but must be sealed.
Myth: It contains asbestos. Fact: Modern boards are asbestos-free.
Myth: It’s maintenance-free. Fact: It requires repainting/resealing over time.
MgO Board
Myth: It’s too expensive. Fact: Installation and maintenance savings offset higher material costs.
Myth: It’s hard to work with. Fact: It is lighter and easier to cut than cement board.
FAQ
What is the main difference? Fiber cement is denser and lasts longer; MgO is lighter, more fire-resistant, and water-impermeable.
Can you paint them? Yes. Fiber cement requires exterior-grade paint. MgO accepts paint, tile, or wallpaper (follow manufacturer guidelines).
Are they pest-resistant? Yes, both are highly resistant to insects and rodents.
Which is easier to DIY? The MgO board is easier to work with due to its lower weight and simple cutting method.
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