For porous substrates including CFC sheet, concrete, masonry, and jointing compound over plasterboard, ARDEX Multiprime prepares the surface to improve the adhesion of subsequent approved ARDEX products. This water-based liquid primer dries quickly in both internal and external applications, providing a reliable bond interface across varying substrate porosities.
Multiprime penetrates porous substrates to bind residual fine dust and equalise suction. By regulating the absorption rate of the surface, it prevents subsequent screeds, renders, or adhesives from losing water too rapidly into the substrate, preserving their strength and curing characteristics. The primer cures to a tough film with a minimum tensile strength of 5.03 MPa and a Shore Hardness A rating of 90, establishing a high-strength mechanical key on porous materials like autoclaved aerated concrete (AAC), screeds, and concrete blocks.
Remove all dirt, dust, curing compounds, oils, grease, surface sealers, existing coatings, and other contaminants before applying. Prepare the surface to ensure it is clean, dry, sound, and free from sharp edges. Damaged concrete between 2mm and 30mm deep should be repaired with ARDEX A 46 before priming. Spalling concrete must be treated using the ARDEX Concrete Repair range, such as ARDEX BR 345.
Shake the container thoroughly before use. Apply evenly with a brush, roller, or sponge to the prepared substrate. Ensure the primer is completely dry before applying any subsequent ARDEX products. Clean all application tools and equipment with water and detergent before the primer dries; cured material requires mechanical removal.
ARDEX Multiprime is suitable for various porous substrates including concrete, render, screed, masonry, concrete blocks, CFC sheet, jointing compound over plasterboard, and autoclaved aerated concrete (AAC).
ARDEX Multiprime dries within 15 to 30 minutes at 23ºC and 50% relative humidity. Drying times can vary based on substrate porosity and site weather conditions.
No, ARDEX Multiprime is not designed for high moisture substrates. If concrete or masonry moisture content exceeds 80% relative humidity or 15g/m²/24hrs, a minimum of two coats of ARDEX WPM 300 (HydrEpoxy) must be used as the primer.
Apply ARDEX Multiprime only when both ambient and substrate temperatures are between 10°C and 35°C. Avoid application outside this range to ensure proper performance.
A second coat of ARDEX Multiprime is specifically required for very porous substrates such as autoclaved aerated concrete (AAC) to ensure adequate sealing and adhesion.
| Application | Key benefit | Primary trades |
|---|---|---|
| Priming concrete, render & screed floors | Ensures strong, reliable adhesion for subsequent ARDEX levelling compounds or waterproofing membranes on porous cementitious substrates. | Concreters, Tilers, Waterproofers, Flooring contractors |
| Preparing autoclaved aerated concrete (AAC) | Seals highly porous AAC surfaces, preventing excessive absorption from subsequent ARDEX finishes and improving bond. | Block layers, Renderers, Builders |
| Priming CFC sheet | Provides a prepared, consistent surface for optimal bonding of ARDEX tile adhesives or waterproofing systems. | Tilers, Waterproofers |
| Priming jointing compound over plasterboard | Enhances adhesion and reduces porosity, creating a stable base for ARDEX decorative finishes or waterproofing applications. | Plasterers, Painters, Waterproofers |
| Internal & external porous substrates | Offers quick drying and low VOC formulation for versatile use across various site conditions, both indoors and outdoors. | General builders, All trades requiring substrate preparation |
The substrate is the foundation of your job. It must be sound, clean, dry, and free from any contaminants like dust, oil, or curing compounds. Mechanically prepare the surface and vacuum away all dust for a professional result.
Shake the pail of Ardex Multiprime thoroughly before use. Do not dilute or add any other substances. Apply a single, even coat to the prepared substrate.
Use your preferred tool to work the primer into the surface, ensuring complete and uniform coverage without ponding or pooling.
Allow the primer to dry completely before applying any subsequent products. The primer should be clear and non-tacky to the touch.
Warning: May cause an allergic skin reaction.
Wear protective gloves (e.g., nitrile rubber, butyl rubber), safety glasses with side shields or chemical goggles, and protective clothing such as overalls and a PVC apron. Use safety footwear. A suitable respirator with a BAX filter may be required if risk of overexposure to mist/vapours exists.
Ensure good ventilation. General exhaust is typically adequate under normal conditions. Local exhaust ventilation may be required in specific circumstances, particularly when breathing mist/vapours/spray cannot be avoided.
Store in original unopened packaging in a dry place at 23ºC and 50% R.H. Shelf life is 12 months. Dispose of contents and container to an authorised hazardous or special waste collection point in accordance with local regulations.
Proper substrate preparation and priming are critical for achieving durable adhesion with ARDEX products.
Surface prep: Remove all dirt, dust, curing compounds, oils, grease, surface sealers, and any other contaminants using mechanical methods and vacuum cleaning. The surface must be sound, clean, dry, and free from sharp edges or loose materials. Repair damaged concrete (2-30mm) with ARDEX A 46, and spalling concrete with ARDEX BR 345.
Primer: Required. Apply one coat. For moisture content exceeding 80% RH or 15g/m²/24hrs, use two coats of ARDEX WPM 300 (HydrEpoxy) instead of Multiprime.
Surface prep: Ensure the surface is clean, dry, and free from dust and contaminants. Mechanically clean as needed.
Primer: Required. Apply one coat.
Surface prep: Confirm the jointing compound is fully cured, dry, and sanded smooth. Remove all dust.
Primer: Required. Apply one coat.
Surface prep: Clean the surface thoroughly, removing any loose material, dust, or contaminants.
Primer: Required. Apply a second coat after the first has dried due to the very porous nature of AAC.
| Property | Value |
|---|---|
| Colour | White |
| Form | Liquid |
| Shore Hardness A | 90 |
| Specific Gravity | 1.19 g/cm³ |
| Service Temperature | 0ºC - 80ºC |
| Tensile Strength (Min) | 5.03 MPa |
| Drying Time | 15 - 30 minutes (@ 23ºC / 50% R.H) |
| Coverage | 8m² - 9m² per 15L pail (two coat application) |
| pH (as supplied) | 8.0 |
| Initial Boiling Point | 100 °C |
| Vapour Pressure | 2.26 kPa @ 20C |
| Solubility in Water | Partly miscible |
| Vapour Density (Air = 1) | <1 |
Here are some common examples on where Ardex Multiprime Primer used by our customers.
