Repair Systems — Concrete & Structural Defects
Moisture suppression primers
Technical product reference for two-part epoxy and single-component acrylic primers that suppress moisture vapour from magnesite and concrete substrates before self-levelling underlayment application. Critical for preventing osmotic blistering and SLC delamination in Australian Class 2 strata buildings.
Product Reference
Individual products — one card each — scroll to view all
Ardex Australia
Ardex MC Rapid
Two-part epoxy moisture-control primer
Ardex MC Rapid is a two-part epoxy moisture-control primer for elevated-RH substrates such as encapsulated magnesite — a single low-viscosity coat forms a moisture barrier so self-levelling underlayments bond without osmotic blistering.
Sika Australia
Sika Primer MB
Two-part epoxy moisture-suppressing floor primer
Sika Primer MB is a two-component solvent-free epoxy primer that suppresses moisture-vapour transmission from problematic substrates including over magnesite floors, so self-levelling compounds bond without osmotic blistering.
Mapei Australia
Mapei Mapeproof Primer
Two-part epoxy moisture barrier / DPM primer
Mapei Mapeproof Primer is a two-part epoxy moisture-vapour barrier / DPM primer for high-RH and encapsulated magnesite floor substrates, applied before self-levelling underlayments so they bond without osmotic blistering. TODO: confirm the maximum substrate RH rated over, number of coats, coverage and pack size from the current Mapei Australia TDS.
Mapei Australia
Mapei Triblock P
Three-component epoxy-cementitious moisture / DPM primer
Mapei Triblock P is a three-component epoxy-cementitious moisture-tolerant primer / DPM for damp and high-RH floor substrates such as encapsulated magnesite, applied before self-levelling underlayments. TODO: confirm the maximum substrate RH rated over, number of coats, coverage and pack size from the current Mapei Australia TDS.
Ardex Australia
Ardex WPM 300
Two-part epoxy moisture vapour barrier
Ardex WPM 300 is a two-part epoxy moisture-vapour barrier for controlling residual substrate moisture on high-RH and encapsulated magnesite floors before levelling compounds are applied. TODO: confirm the maximum substrate RH rated over, number of coats, coverage and pack size from the current Ardex Australia TDS.
System Comparison
Magnesite flooring deterioration — confirm all selections against the current manufacturer TDS before specifying.
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Do not confuse moisture suppression primers with:
- Self-levelling underlayment adhesion primers (standard acrylic) — standard single-component acrylic adhesion primers (Mapei Eco Prim T, Ardex P 51 in adhesion-primer mode) improve SLC bond but do NOT suppress moisture vapour; they must never be used on high-RH magnesite substrates as a substitute for a two-part epoxy moisture barrier primer
- Bonding agents and SBR latex — SBR-latex bonding agents (Ardex P 51, Sika Latex SBR) used for cementitious repair mortar application on walls are not moisture barrier products; they are adhesion promoters for vertical repair applications and are entirely different from moisture suppression floor primers
- Epoxy floor coatings and sealers (Sika Sikafloor, Fosroc Nitocote EP) — epoxy floor coatings are surface-applied protective barriers on fully cured concrete; they are decorative or protective coatings and not moisture primer systems for floor levelling; applying SLC over an epoxy coating without appropriate primer causes delamination
- Vapour barriers in new construction (polyethylene membrane, Sisalation) — under-slab plastic vapour barriers are structural construction elements installed during concrete slab construction; they are not the same as moisture suppression floor primers applied to existing magnesite or concrete surfaces during remediation
- Penetrating concrete sealers (silane, siloxane waterproofing) — penetrating water repellents seal against liquid water ingress from the surface; they do not suppress moisture vapour drive from within the slab and are not suitable as moisture barrier primers under floor levelling compounds
Disclaimer
This page provides general technical information only. Final product selection must be confirmed against the current manufacturer TDS, project specification, substrate condition, and applicable standards. Do not rely on this reference as a substitute for professional engineering advice.