Fire Rated Roofing Sheathing

Product Introduction

As a roof sheathing material (i.e., the protective panel for the outer or base layer of a roof), magnesium oxide board (MgO board) derives its fire resistance from its inorganic material properties and structural design, exhibiting outstanding performance in resisting fire spread and ensuring the safety of roof structures. The following details its fire resistance as roof sheathing from multiple core dimensions:

 

1. Inherent Non-Combustible Property Determined by Material Nature, Reaching the Highest Fire Resistance Rating

Roof sheathing serves as the first line of defense for buildings against external fire sources (such as fires from adjacent buildings, ignition by fireworks, fire caused by lightning strikes, etc.) and the spread of internal fires. The combustion performance of the material is a core indicator.
The main components of MgO board are magnesium oxide (MgO), magnesium chloride (MgCl₂)/magnesium sulfate(MgSo4), and inorganic materials such as glass fiber cloth, without any organic combustible components. According to the national standard GB 8624-2012 Classification for Burning Behavior of Building Materials and Products, its combustion performance reaches Class A1 (non-combustible material), with specific manifestations as follows:

Not ignited by open flame: Even when in direct contact with flame (such as flame jet, high-temperature baking), it will not sustain combustion, leaving no burning traces after the fire source is removed;

No risk of flame propagation: Unlike asphalt shingles (combustible), PVC roof membranes (flammable), or wooden sheathing (flammable), it will not cause flame spread after local ignition, effectively preventing the fire from spreading along the roof surface;

No combustibles generated at high temperatures: Under the action of high fire temperatures (usually 800-1200℃), it will not decompose into combustible gases such as methane and formaldehyde, avoiding the combustion-supporting effect of "gas combustion".

 

2. Maintaining Structural Stability at High Temperatures, Delaying Roof Collapse

If the roof collapses during a fire, it will not only cause the fire to spread rapidly into the building but also threaten the safety of rescue personnel. As roof sheathing, the structural stability of MgO board in high-temperature environments is its key fire-resistant advantage:

High-temperature resistance limit far exceeds fire temperature: The melting point of magnesium oxide, the core component, is as high as 2800℃, and the decomposition temperature of magnesium chloride is about 1400℃, both much higher than the temperature of most building fires (800-1200℃). In a fire, MgO board will not lose structural support like metal plates (such as aluminum alloy, with a melting point of 660℃, prone to softening and deformation at high temperatures) or asphalt-based materials (melting and flowing when exposed to high temperatures);

Low shrinkage and anti-deformation ability: The linear shrinkage rate at high temperatures is <0.3%, with almost no warping, cracking, or bulging. It can maintain adhesion to the roof base (such as purlins, insulation layers) for a long time, avoiding flame penetration due to gaps;

Fire resistance limit significantly better than traditional materials: Depending on the thickness (12-15mm commonly used for roof sheathing) and structural design (such as whether it is matched with fire-resistant keels or insulation layers), its fire resistance limit can reach 2-4 hours, far exceeding that of asphalt shingles (within 0.1 hours) and ordinary color steel plates (about 0.25 hours), buying time for personnel evacuation and fire fighting.

 

3. Preventing Flame Penetration and Heat Transfer, Blocking Fire Spread Paths

Another important fire-resistant function of roof sheathing is to prevent flames from invading the building interior from the outside or  the outside from the inside. MgO board achieves this through its dense structure and low thermal conductivity:

Dense structure blocks flame penetration: The dense structure formed by its inorganic cementitious system can effectively block the penetration of flames and high-temperature airflow. Even when locally burned by high-temperature flames, it will not form flame channels like wooden plates (easily burned through) or plastic plates (melting to form holes);

Low thermal conductivity delays heat transfer: The thermal conductivity is only 0.15-0.25W/(m·K) (far lower than that of metal plates, which is 100-300W/(m·K)), which can reduce the transfer of high temperature to the inner side of the roof (such as insulation layers, ceilings), avoiding the ignition of combustibles on the inner side (if the roof insulation layer is a combustible material, it needs to rely on the sheathing to block heat);

Suppressing the "chimney effect": In the event of a fire inside the building, high-temperature flue gas tends to form a "chimney effect" through roof gaps to accelerate spread. The dimensional stability of MgO board can keep the joints tight, reducing the leakage of flue gas or the entry of external air to fuel the fire.

 

4. No Smoke or Toxicity When Burned, Reducing Secondary Fire Hazards

In fires, smoke and toxic gases generated by the combustion of roof materials are important factors threatening life safety. MgO board has significant advantages in terms of smoke characteristics at extremely high temperatures:

No release of toxic gases: Its inorganic components only produce inert inorganic substances such as magnesium oxide and magnesium chloride after high-temperature decomposition, without toxic gases such as formaldehyde, carbon monoxide, and hydrogen chloride (these gases are the main fatal factors when organic materials burn);

Negligible smoke production: Since no combustion reaction occurs, MgO board produces almost no smoke at high temperatures, avoiding the problem of dense smoke obscuring vision and hindering evacuation and fire fighting, which is common in the combustion of traditional roof materials (such as PVC and asphalt).

 

5. Fire Resistance Advantages Compared with Traditional Roof Sheathing Materials

Roof Sheathing Material	Fire Resistance Rating	Performance at High Temperatures	Smoke and Toxicity	Risk of Flame Penetration
MgO Board	Class A1 (Non-combustible)	No deformation, no melting, stable structure	No smoke, non-toxic	Extremely low (blocked by dense structure)
Asphalt Shingles	Class B2 (Combustible)	Melt and flow at high temperatures, fueling the fire	Dense smoke, releasing toxic gases (such as benzene)	High (easily burned through)
Color Steel Plate (Sandwich)	Class B1-B2	Metal layer deforms at high temperatures, sandwich is flammable (such as foam)	Dense smoke, highly toxic (depending on the sandwich)	High (penetration after sandwich burns)
Wooden Sheathing Board	Class B3 (Flammable)	Burns quickly, loses structural strength	Dense smoke, releasing carbon monoxide	Extremely high

 

6. Applicable Scenarios: Roof Systems with High Fire Resistance Requirements

MgO board, as roof sheathing, is particularly suitable for scenarios with strict fire resistance requirements:

Public buildings: Roofs of hospitals, schools, and shopping malls (with dense crowds, serious consequences of fire risks);

Industrial buildings: Factories and warehouses (may have flammable materials or high-temperature operations);

Buildings around flammable and explosive places: Roofs of buildings near oil depots and chemical plants (need to block the spread of external fires);

Historic buildings or cultural relic protection buildings: Need to improve fire resistance without damaging the original appearance, and MgO board can be used as concealed sheathing to enhance safety.

 

Summary

As roof sheathing, the core of MgO board's fire resistance lies in its Class A1 non-combustible property, structural stability at high temperatures, flame penetration blocking ability, and smoke-free and non-toxic characteristics. It fundamentally solves the pain points of traditional roof materials such as flammability, easy failure at high temperatures, and high smoke toxicity. It can effectively block fire spread paths, delay roof collapse time, and reduce secondary hazards, making it an ideal choice for roof systems of buildings with high fire resistance requirements.

 

Parameter

Main Materials	MgO, MgCl2/MgSO4, Glass fiber Mesh
Fire Performance	Non-combustible, No flame spread, No smoke spread,No poisonous gas
Density	1-1.25kg/m3,
Flexural Strength	16-25Mpa
Impact Strength	≥3.5 kJ/m2
Moisture Content	≤8%
Shrinkage	≤0.3%
Swelling	≤0.3%
Screw Holding Capacity	50-100/(N/mm)
Leachable Chloride	0.1%(MOS),3%(MOC)
Edge	Square/T&G/Tapered/Beveled
Thickness	12-16mm
Standard Sizes	4*8ft/1.22*2.44m(Other sizes can be customized)
Production Capacity	5000 square meters / day
Remark	The above parameters are acceptable to ODM

 

 

Factory

 

About Us

We are dedicated to producing magnesia cement products. Our mission is to supply the global construction market with environmentally friendly, high-performance, and sustainable green materials.

We emphasize quality control and consistency in our MgO products. Every batch is tested in our laboratory, and each panel is inspected before packaging.

Our primary products include Magnesium Oxide Boards (MgO Boards) for construction and laminated MgO boards for furniture and decoration.

 

Packing and Shipping

 

FAQ

Q: Can you customize products according to our specifications?
A: Yes, we offer OEM and ODM services.

 

Q: What is your packaging?
A: We use plywood or solid wood pallets for packaging.

 

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