Fiber cement board, while naturally moisture-resistant, is not inherently waterproof on its own and often requires additional treatment for wet areas or exterior use.
Here are the main ways to waterproof fiber cement board, depending on the application (e.g., shower walls, exterior siding):
This is the most common application where complete waterproofing is critical, usually before tiling.
The primary risk associated with “free chlorides” in Magnesium Oxide (MgO) boards is accelerated corrosion of metal building components and significant moisture damage to the structure
This risk is almost exclusively tied to older formulations of MgO boards that use magnesium chloride (MgCl2) as the binding agent (known as magnesium oxychloride cement).
Key Risks of Free Chlorides
The “weeping” or “sweating” issue is a significant problem primarily associated with older-style Magnesium Chloride boards, a type of Magnesium Oxide board.
It is a process where the board draws moisture from the air, causing salty, corrosive liquid droplets to form and leak from its surface.
What Is Weeping or Sweating?
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No, MgSO4 (sulfate-based) boards and MgCl2 (chloride-based) boards generally have the same high fire rating in their initial, dry state. The difference lies in the long-term stability of that rating in real-world, high-humidity applications.
Both types of boards are built primarily on Magnesium Oxide (MgO) cement, which is inherently non-combustible
In laboratory tests, both MgSo4 and MgCl2 boards typically ...
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The question of whether MgSO4 board is a structural sheathing material is complex and depends on the specific product and its code approval, but the general answer is Yes, specific, high-density MgSO4 formulations are engineered and approved for use as structural sheathing
Here is a breakdown:
Magnesium Sulfate (MgSO4) Board is unequivocally more suitable for high-humidity and exterior applications than Magnesium Chloride (MgCl2) Board.
The reason is the absence of high concentrations of chloride ions in the (MgSO4) formulation, which eliminates the core problems associated with (MgSO4)boards in wet environments:
An MGO (Magnesium Oxide) board is generally considered a safe and environmentally friendly building material, often marketed as a greener alternative to traditional options like gypsum drywall and cement board.
Here is a detailed breakdown of its safety and environmental attributes, along with a crucial safety consideration：
Safety and Health Profile
MGO boards have several characteristics that make them a safe choice for ...
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MGO Board Fire Resistance Official Ratings
Magnesium Oxide (MgO) boards are officially rated for fire resistance using various international standards that categorize their non-combustibility and the fire-resistance duration of the assembly they are part of.
Here are the key official ratings and standards for MgO boards:
Reaction to Fire Classification (Non-Combustibility)
This classification determines if the material itself will contribute fuel to a ...
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Yes, Magnesium Oxide (MgO) board can be corrosive to metal fasteners and framing, but the risk largely depends on the board’s composition and the environmental conditions.
The primary factor is the presence of magnesium chloride as a binding agent, which is common in traditional or lower-quality MgO boards.
The Cause of Corrosion
The corrosion risk stems from the chloride content in the ...
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Yes, some types of Magnesium Oxide (MgO) boards can “sweat” or leach fluid in humid conditions due to a process similar to deliquescence.
This phenomenon, often called “crying” or “sweating” boards, is a serious concern primarily associated with MgO boards that use magnesium chloride as a binding agent, which forms magnesium oxychloride cement (MOC).
The Mechanism of Leaching/Sweating
The “sweating” is a ...
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