FloorSure TECHNICAL
FloorSure is a precision-manufactured, high-strength, structural MOS cement floor board
MgO boards - Two Chemistries:
MOS vs MOC
MOS — Magnesium Oxysulphate
Sulphate-based binder: magnesium oxide, magnesium sulphate (non-chloride) and water.
Moisture behaviour: no leaching of chloride-rich moisture; performs similarly to fibre cement boards. Negligible corrosion risk - Literally thousands of MOS boards have been sold in Australia with no corrosion issues.
MgO (magnesium oxide) board is often discussed as if it were a single material with a single history.
MgO board is NOT a single material.
There are two binder chemistries, MOS and MOC, which vary in composition and performance.
MOC — Magnesium Oxychloride
Chloride-based binder: magnesium oxide, magnesium chloride and water.
Moisture behaviour: some MOC boards have leached chloride-rich moisture, corroding adjacent materials and metals - Past issues have been documented in Australia and overseas.
Every documented corrosion-related failure attributed to MgO board sits in the right/red MOC column.
Chloride is the mechanism. It attracts moisture, dissolves into it, migrates through the board to the surface, and corrodes the metal it reaches. Remove the chloride and the mechanism goes with it.
FloorSure’s formulation is MOS → Non-Chloride with Negligible Corrosion Risk
FloorSure’s leachable chloride ion content has been tested to a barely discernible 0.02%.
Ironically, a concrete panel supplier seeking to denigrate all MgO boards as being corrosive, has a leachable chloride ion content of 0.13% - 6x higher than FloorSure’s
Structural Floor Boards - Strength & Load Capacities
The key performance measures for any structural floor board are:
Bending strength or MOR (modulus of rupture).
Stiffness or MOE (modulus of elasticity).
Resultant Load Capacities.
FloorSure is fibre-reinforced and extremely strong. In fact, FloorSure has a bending strength up to 5x greater than some of its competitor products. Further, FloorSure can span up to 600mm joist centres and be used for residential and commercial applications. Check out FloorSure’s Design & Load Tables—you’ll be pleasantly surprised about its many potential applications.
On the flipside, be careful of assertions of “25 MPa Compressive strength” (or, sometimes, just “25 MPa” with no qualification/explanation). A board spanning joists is loaded in bending - It fails in flexure, not compression. Compressive strength is meaningless as a stand-alone claim of floor-spanning capacity. A structural floor board must be assessed by its bending strength, stiffness and verified load capacities. Presenting a compression figure as proof of performance between joists is misleading.
BlueScope / TRUECORE®
Steel Framing
BlueScope’s Technical Bulletin TB-34 requires an isolation method between so-called “incompatible materials” and TRUECORE® steel.
MgO boards are specifically listed. Thus, for correct installation of FloorSure on TRUECORE® steel, use a suitable isolation membrane, or an air gap where appropriate, and compatible fixings.
The same rule applies to moisture-retaining materials. TB-34 also lists “Any material likely to retain moisture for extended periods”. Concrete, fibre cement and AAC boards are porous and retain moisture for extended periods. Thus, they too require isolation.
IMPORTANT: Do not accept blanket claims that concrete panels can be installed directly on TRUECORE®. Advice to omit required isolation contradicts BlueScope’s TB-34 and can compromise your BlueScope warranty cover. A seller’s assurance does not override BlueScope’s requirements.
Airborne Sound Insulation
Mass matters. When comparing bare boards, weight per square metre (kg/m²) is the main driver of airborne sound insulation. Heavier boards generally block more airborne sound. This is the so-called “mass-law principle”. Thus, bare boards with the same weight per square metre will have very similar airborne sound insulation.
The complete floor/ceiling construction determines performance. Results depend on the floor substrate (bare board) plus: finishes, joist type and centres, cavity depth, insulation, ceiling lining and number of layers, furring channels and resilient mounts. Sealing, penetrations and sound travelling through adjoining structures also affect installed performance.
FloorSure is transparent and publishes the details. Our INSUL assessments cover the bare FloorSure board and 24 floor/ceiling configurations, helping you identify a configuration suited to your build and acoustic requirements. These are predicted ratings for the specified construction configurations.
Challenge unexplained acoustic claims:
A 35mm concrete panel supplier advertises Rw+Ctr 60 without disclosing the complete floor/ceiling construction. Presenting this as the board’s acoustic performance is misleading (a complete floor/ceiling rating must not be passed off as a board rating). FloorSure and this concrete panel have similar weights per square metre and very similar assessed bare-board performance—Rw 35 for both. These assessments provide no basis for either board to claim significant acoustic superiority. Ignore any attempt to do so.
The same 35mm concrete-board supplier also advertises superiority to a 150mm concrete slab without providing the complete construction details and supporting evidence for both systems. That does not establish superiority; it presents an unsupported comparison as fact.
MOS Chemistry and Water Resistance
MOS hardens through a chemical reaction. Magnesium oxide, magnesium sulphate and water react to form a hardened crystalline cement binder. This is an exothermic reaction, meaning it releases heat.
The crystal structure matters. Formulation, additives and manufacturing conditions determine which crystal structures develop. Some are vulnerable to sustained moisture; the desirable phase provides high strength and excellent water resistance. Achieving it consistently requires precise manufacturing control.
FloorSure controls and verifies the result. Specialist academic guidance and oversight, extensive trials, and precise control of formulation and additives enable FloorSure to consistently form the desirable phase. Ecobuild Solutions regularly tests the boards’ crystal structure to verify its predominance.
FloorSure is highly water-resistant given its consistent formation of the desirable phase / crystal structure. Further, following normal wetting, modest reductions in wet-state strength are substantially recovered as the board dries (similar to fibre cement boards). Temporary wet-state changes do not demonstrate permanent deterioration every time a board gets wet.
Some competitors have called hardened MOS “Epsom salts” - This confuses an ingredient with the finished compound. By that reasoning, table salt could be dismissed as poisonous chlorine gas because chlorine reacts with sodium to form it. Likewise, hardened concrete would still be loose cement powder. That is a misunderstanding of basic chemistry: chemical reactions create materials with different structures and properties.
Thermal Mass
Thermal mass is a material’s ability to absorb, store and release heat, helping moderate indoor temperature fluctuations.
Thermal mass and insulation do different jobs: thermal mass stores heat; insulation slows heat transfer. They work together to improve a building’s thermal performance.
Calculation: Density x Specific Heat Capacity (= Capacitance) x Thickness (in metres) = Thermal Mass, expressed in kJ/m²·K.
Specific Heat Capacity (SHC) determines how much heat each kilogram can store for a 1°C temperature rise. When comparing boards of similar weight per square metre, SHC is the primary driver of differences in thermal mass.
MOS’s hydrated binder contributes to its high SHC. Water chemically bound within the hardened binder contributes to its capacity to absorb and store heat.
FloorSure delivers approximately 60 kJ/m²·K. Independent SHC testing of our MOS boards, combined with FloorSure’s density and 30 mm thickness, establishes this thermal mass—the highest among the flooring products in our comparison.