Ensuring long-term adhesion for ARDEX waterproofing membranes and levelling compounds starts with a solid foundation. ARDEX Multiprime provides that reliable base, preventing bond failures on porous substrates by creating an optimal surface for subsequent ARDEX systems. It’s the critical first step for confidence in your build.

Why this product exists

ARDEX Multiprime is a water-based primer formulated to enhance the adhesion of approved ARDEX products to a range of porous substrates. It seals and prepares surfaces like concrete, screed, and autoclaved aerated concrete (AAC), promoting a stronger bond for membranes and finishes. Its low VOC and quick-drying properties support efficient work cycles for both internal and external applications.

The numbers that matter

  • Drying time: 15-30 minutes at 23°C and 50% relative humidity. This rapid drying minimises downtime, allowing for quicker application of subsequent ARDEX products and maintaining project schedules.
  • Coverage: 8-9m² per 15L pail for a two-coat application. This coverage rate provides clarity for material estimation, reducing waste and ensuring adequate priming for demanding porous surfaces.
  • Service temperature: 0ºC to 80ºC. This broad operational range ensures the primer remains stable and effective across typical Australian internal and external environmental conditions, from cool mornings to hot afternoons.

What it's like to use

ARDEX Multiprime is applied by brush, roller, or sponge after thorough substrate preparation. Ensure the contents are well-shaken before use. For highly porous substrates like AAC, a second coat is necessary to achieve the desired surface sealing and adhesion promotion. Clean all equipment with water and detergent immediately after use, before the product has a chance to dry, as cured material requires mechanical removal.

Where this product excels

ARDEX Multiprime provides essential adhesion and surface preparation in critical build-ups:

  • Wet areas: bathrooms, showers, laundries, and kitchens. Here, it serves as a primer for waterproofing systems on concrete, render, and screed, ensuring the membrane bonds securely to the substrate.
  • Roofing: concrete roofs and membrane-covered tiled areas. This primer is effective as a reprimer for built-up or filled areas, preparing the surface for subsequent layers in a robust roofing system.
  • Balconies, podiums, door/window reveals, and flashings. Its role as a reprimer in these exposed areas contributes to the long-term integrity of waterproofing and sealing applications.

How it fits in a real system

This product consistently appears early in the build sequence, typically after initial substrate preparation and crack sealing, but before the main waterproofing membrane is applied. In a concrete roof terrace system, ARDEX Multiprime is often applied as the third step, following a vapour barrier (Everflex VBS) and joint sealant (Adheseal Hi-Flex 50 MS sealant), creating a keyable surface for the subsequent TuffTop or Everflex VBS layers. This positioning is crucial for establishing strong, long-lasting adhesion for the entire system.

Choose this when

  • When priming porous substrates like concrete, render, screed, or CFC sheet to improve adhesion for approved ARDEX products.
  • When working in wet areas such as bathrooms, laundries, or kitchens, requiring a reliable primer for waterproofing systems.
  • When reprofiling or re-priming areas on concrete roofs, balconies, or podiums before applying new membranes or finishes.
  • When you require a low VOC, quick-drying primer suitable for both internal and external use within a suitable temperature range.

Don't use this when

  • Not for: Substrates with high moisture content. If masonry or concrete moisture exceeds 80% relative humidity (ASTM F2170) or 15g/m²/24hrs (ASTM F1869), ARDEX WPM 300 (HydrEpoxy) is the required primer.
  • Not for: Application when ambient or substrate temperatures are below 10°C or above 35°C, as this can affect proper adhesion and curing.
  • Not for: Dilution. Do not add solvent or water, as this compromises the primer's formulation and performance.
  • Not for: Application if rain is imminent, as moisture can interfere with the drying and bonding process.

This water-based formulation has a low VOC content, supporting environmental and health considerations on the job site.