MGO Sheathing or Plywood? Honest Material Comparison for Contractors

The differences between MGO sheathing and traditional plywood can substantially affect your construction project's safety and longevity. Contractors often struggle to pick materials that give the best value for money. MGO boards are a game-changer because they maintain structural integrity at temperatures up to 800 degrees Fahrenheit. This makes them reliable choices for modern construction projects.

MGO board is a technologically advanced building material that outperforms traditional wood products. Traditional plywood has been the go-to choice for decades. However, MGO wall sheathing proves superior with only 0.34% moisture absorption. This exceptional water resistance makes it perfect for wet environments. The material matches OSB and plywood in structural values. DuPont ArmorBoard structural sheathing, at half-inch thickness, handles maximum shear stress over 280 psf. MGO sheathing also resists fire, moisture, and pests effectively. These features solve many common construction site problems.

Let's learn about both materials by looking at their composition, moisture resistance, fire safety, durability, and cost. This comparison will help you pick the right material for your project needs.

Jinpeng Group -- MagMatrix BMSC 517 New Sulfate MGO Fire Rated Structurally Rated Exterior Wall Sheathing Panel

Material Composition and Structure

The way construction materials are made tells us a lot about how well they work. Let's get into the differences between MGO sheathing and plywood.

What is MGO sheathing board made of?

MGO sheathing comes from a specific mix of minerals and reinforcement materials. Magnesium oxide powder forms the foundation of these boards and makes up about 56-58% of what's in them. This mineral comes from calcined magnesite—they heat magnesite to remove carbon dioxide.

Today's MGO boards use magnesium sulfate (27-29%) to bind everything together, which is different from the older versions that used magnesium chloride. This change happened because boards with sulfate are better at keeping water out and don't rust as much.

These components give MGO its special qualities:

·       Perlite (3-4%): A volcanic glass that expands with heat. It makes the board lighter and better at insulating heat and fighting fire

·       Wood fibers (5-6%): Help make the board strong and flexible

·       Fiberglass mesh (4-6%): Makes the board tough and resistant to impacts

The manufacturing process mixes these materials into a slurry that turns into boards under specific conditions. This creates a tough, rock-like material through chemical bonds.

How plywood is manufactured

Plywood is different - it's just wood veneers (thin layers of wood) stuck together with glue. Making it takes several careful steps.

The process starts with picking good logs, removing their bark, and cutting them to the right size. Big machines called lathes spin these logs against sharp blades to make thin veneer sheets, usually about 3mm (1/8 inch) thick.

After peeling, they dry the veneers until they have just 1-15% moisture left, though outer layers can keep up to 25%. They use temperatures between 150-200°C (300-400°F) for drying.

The dried veneers get coated with special resin before being stacked with their grains going different ways - this is vital for strength. They use two main types of glue: phenol-formaldehyde for softwood and outdoor hardwood plywood, and urea-formaldehyde for indoor hardwood plywood.

The final step heats and presses everything together. Softwood plywood needs 132-165°C (270-330°F), while hardwood plywood needs 107-135°C (225-275°F). This takes between 2-7 minutes.

Key differences in material makeup

The biggest difference between these materials is what they're made of - MGO sheathing uses minerals with some organic fibers, but plywood is all wood.

This basic difference explains why they behave differently. MGO boards are strong because of how their minerals bond together, while plywood gets its strength from how the wood layers are arranged.

Half-inch DuPont ArmorBoard structural sheathing can handle shear stress over 280 psf, which matches traditional wood products. A single #10-13 pancake head screw in MGO sheathing can hold more than 155 lbs - this is a big deal as it means that it's much stronger than the usual 32 lbs requirement.

Moisture and Mold Resistance

Water resistance plays a crucial role in choosing materials for modern construction projects. The way MGO sheathing and plywood handle moisture can make a huge difference in how long a project lasts and how much maintenance it needs.

Water absorption: 0.34% vs higher in plywood

MGO sheathing stands out with its low water absorption rate of just 0.34%. This minimal absorption stops common issues like swelling, warping, and delamination that other materials face. MGO boards keep almost 100% of their flexural strength even after 25 cycles of soaking and drying.

Plywood performs better than drywall but still has major moisture limitations. It loses about 9% of its bending strength during wet-dry cycling. Water exposure makes plywood warp, cup, and can cause structural failure in worst cases. The material absorbs much more moisture than MGO wall sheathing, which leads to size changes and instability.

Mold resistance: ASTM G21 results

MGO sheathing proves its superior mold resistance through the ASTM G21 fungal test. These boards consistently earn a perfect 0/0/0 rating, which means zero mold growth. The inorganic makeup of magnesium oxide boards naturally prevents mold and mildew from growing.

Studies label plywood as "mold prone". Wood's organic structure gives fungi a perfect place to grow, especially with moisture present. Plywood can't match MGO boards' natural mold resistance, despite various available treatments.

Performance in wet environments like bathrooms and basements

MGO sheathing works great in moisture-prone areas such as bathrooms, basements, kitchens, and pool areas. The material stays strong in high-humidity environments without breaking down. MGO boards help keep indoor air clean by stopping mold growth, which means less maintenance.

Marine plywood offers better moisture handling, but standard plywood needs extra treatments or protective coatings to work well in damp conditions. Yet even with these treatments, it can't match MGO boards' natural moisture resistance.

MGO sheathing beats plywood in every moisture-handling test. This difference matters a lot to contractors in humid regions or areas with frequent rain because it helps buildings last longer and cuts down on maintenance costs.

Fire Safety and Heat Resistance

Fire performance is a vital factor contractors consider to select construction materials. It determines building code compliance and insurance rates. MgO sheathing and plywood show major differences in this category.

Combustibility: Non-combustible vs combustible

MgO sheathing's mineral-based composition makes it naturally non-combustible. The boards keep their structural integrity without catching fire at temperatures up to 800 degrees Fahrenheit (1,472°F). This impressive heat resistance comes from the material's chemical makeup, which is mostly magnesium oxide.

Plywood, on the other hand, catches fire easily and helps flames spread. Wood-based materials act as fuel during fires. Fire-retardant treatments help, but plywood can't match MgO wall sheathing's natural fire resistance.

Fire rating: Up to 4 hours vs 30 minutes

These materials show huge differences in fire resistance time. Well-made MgO sheathing resists fire from one to four hours in standardized ASTM E119 tests. People get more time to evacuate because of this extended protection. MgO boards stay structurally sound and work as fire barriers by limiting heat transfer.

Regular plywood lasts only about 30 minutes before it starts breaking down. The material loses strength faster once it starts burning. This can lead to collapse and let fire spread between parts of the building. MgO sheathing gives about eight times more fire protection than standard plywood - a huge advantage in emergencies.

Smoke and flame spread ratings

ASTM E84 tests measure flame spread and smoke development to determine fire safety classifications. MgO sheathing gets a Class A fire rating - the best possible - with a flame spread rating of 0/0 in these tests. Flames don't move across the board's surface at all.

The classification system works this way:

Rating Class	Flame Spread Index	Smoke Development
Class A (I)	0-25	450 max
Class B (II)	26-75	450 max
Class C (III)	76-200	450 max

Plywood usually gets Class C ratings because flames spread faster on it. Burning plywood creates lots of smoke and potentially dangerous gasses. MgO boards produce almost no smoke or toxic fumes during fires. This makes a big difference during evacuations because people can see better and face lower inhalation risks.

These fire performance differences often help contractors decide which material to use, especially for projects with strict fire codes like schools, hospitals, or multi-family buildings. MgO sheathing's better fire resistance makes it easier to meet code requirements and can lower insurance costs.

Durability and Lifespan in Real Projects

Construction materials' durability plays a huge role in project success and keeps clients happy. MgO sheathing and plywood each have their own durability characteristics that shape how well they perform as time goes by.

Impact resistance and structural integrity

MgO sheathing shows remarkable impact resistance and doesn't crack or crumble as easily as other options. This toughness makes it great for both load-bearing and non-load-bearing applications. These boards stay stable even with changing temperature and humidity. MgO wall sheathing keeps its shape through different seasons, unlike wood-based products that tend to warp and shrink.

Plywood starts out with good impact strength but can't match MgO boards' stability in the long run. Its layered design gives it original durability, but being organic means it breaks down faster when exposed to environmental stress.

Performance in high-traffic areas

MgO board's mineral makeup gives it an edge in busy spaces. These boards work great in high-traffic spots like corridors, stairwells, and public buildings. Schools, hospitals, and commercial buildings get extra protection from MgO's tough impact resistance. Areas that see daily wear and tear look better and work better much longer when built with MgO sheathing.

Plywood needs replacing more often in these demanding spaces because it just can't handle physical stress like MgO can.

Long-term maintenance needs

These materials need very different levels of maintenance. MgO sheathing needs little upkeep since it naturally fights off pests, fire, and moisture. It keeps termites and carpenter ants away because there's nothing organic in it for them to eat. This feature helps a lot in humid or tropical areas where insects cause constant problems.

Plywood needs more regular care since termites can easily damage it. The costs add up over time - you'll pay more for replacements and deal with more service disruptions. These factors matter to contractors who want happy clients and profitable projects.

Cost vs Long-Term Value

Sound financial decisions for construction projects depend on evaluating both immediate costs and long-term expenses. The economic comparison between mgo sheathing and plywood shows a classic case of upfront investment versus ongoing maintenance costs.

Upfront material and labor costs

MGO wall sheathing costs more than traditional plywood. Magnesium oxide sheathing costs between $1.50 and $3.50 per square foot, while plywood ranges from $0.50 to $2.50 per square foot. This price difference comes from mgo board's advanced material composition.

Material expenses aren't the only factor - labor costs substantially affect project budgets. MGO sheathing installation needs specialized tools and trained workers, which can drive up labor costs. The panels' lightweight nature helps offset some costs by reducing equipment needs and installation time.

Repair and replacement frequency

These materials have dramatically different maintenance needs. Magnesium oxide sheathing needs minimal attention throughout its service life. Its natural resistance to water, mold, and pests eliminates most repair scenarios that plague traditional materials.

Plywood, despite being cheaper at first, ends up costing more in maintenance over time. Moisture damage, insect problems, and warping force repairs or replacements faster, especially in humid environments. Contractors face more service calls and material costs that add up quickly.

Return on investment for contractors

MGO board's financial advantage becomes clear over time. Construction industry data shows mgo sheathing performs better financially over a decade or longer. The extended lifespan makes up for the higher purchase price through fewer replacements, minimal repairs, and lower utility costs from better insulation.

Building expenses follow a predictable pattern: construction costs make up only 10-20% of lifetime expenses, while maintenance and operations take up the remaining 80-90%. MGO board installations can give up to 89% return on investment, mainly through lower maintenance needs and better durability.

Comparison Table

Characteristic	MGO Sheathing	Plywood
Material Composition	- 56-58% magnesium oxide powder- 27-29% magnesium sulfate- 3-4% perlite- 5-6% wood fibers- 4-6% fiberglass mesh	Wood veneers bonded with adhesive
Water Absorption	0.34%	By a lot higher (exact % not specified)
Moisture Performance	Maintains nearly 100% flexural strength after 25 wet-dry cycles	Loses 9% bending strength during wet-dry cycling
Fire Resistance	- Up to 800°F without losing integrity- 1-4 hours fire rating- Flame spread rating: 0/0	- Combustible- ~30 minutes fire rating- Class C fire rating
Mold Resistance	ASTM G21 rating: 0/0/0 (no mold growth)	Classified as "mold prone"
Fastener Strength	>155 lbs withdrawal strength (#10-13 screw)	Not mentioned
Shear Stress	>280 psf (1/2 inch thickness)	Comparable (exact value not specified)
Cost per Square Foot	$1.50 - $3.50	$0.50 - $2.50
Pest Resistance	Naturally repels termites and carpenter ants	Vulnerable to termite infestations
Maintenance Needs	Minimal maintenance required	Regular maintenance needed

Conclusion

The choice between MGO sheathing and plywood boils down to finding the right balance between budget and performance needs. MGO sheathing has proven to be the better performer when compared to traditional plywood in several key areas.

MGO boards stand out with their impressive moisture resistance. They absorb just 0.34% water while plywood takes in much more moisture. This makes MGO boards a great choice for humid areas or places exposed to water. The fire-resistant properties of MGO sheathing offer protection that lasts eight times longer than standard plywood. This is a vital consideration for commercial buildings and multi-family structures with strict safety requirements.

The price difference can't be ignored. MGO sheathing costs $1.50-$3.50 per square foot, while plywood ranges from $0.50-$2.50. Yet this upfront investment pays off through lower maintenance costs over time. MGO's natural resistance to pests, mold, and moisture means fewer repairs and replacements throughout a building's life.

Contractors like us base our decisions on each project's specific needs. MGO's superior properties make it ideal for high-traffic commercial spaces, moisture-prone areas like bathrooms and basements, and buildings with strict fire codes. Traditional plywood might work better for budget-conscious residential projects with shorter lifespans.

Construction keeps evolving. Performance-based materials like MGO sheathing are becoming more popular as clients focus on building longevity and lifecycle costs rather than just upfront expenses. A full understanding of both options helps us provide solutions that match our clients' needs, budgets, and long-term goals. The best choice between MGO sheathing and plywood depends on your project's specific requirements and performance targets.

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