Which Ardex Primer Should I Use? A Complete Guide

Choosing the correct primer is an essential step in floor preparation. Using the right product can improve adhesion, reduce substrate absorbency, strengthen weak surfaces and, in some cases, help manage residual moisture before flooring is installed.

Ardex offers a range of specialist primers, each developed for different substrates and applications. This guide explains what each primer is designed for and when it should be used.

Ardex Primer Comparison

Product	Best For	Key Benefit
Ardex P 7	Non-absorbent substrates	Ready-to-use primer that promotes adhesion on smooth surfaces.
Ardex P 51	Absorbent substrates	Acrylic primer that regulates absorbency before applying levelling compounds.
Ardex P 4	Smooth, dense substrates	Solvent-free primer with excellent adhesion to difficult surfaces.
Ardex P 82	Impervious substrates	Two-part primer for dense, smooth or moisture-sensitive substrates.
Ardex PU 30	Moisture control & consolidation	Polyurethane primer, moisture barrier and substrate consolidator.

Ardex P 7 – Ready-to-Use Universal Primer

Ardex P 7 is a ready-to-use primer designed to improve adhesion on both absorbent and non-absorbent substrates. It's commonly used before applying Ardex levelling compounds and helps create a consistent surface for subsequent flooring preparation.

Ideal for:

• Existing ceramic tiles
• Terrazzo
• Old adhesive residues
• Concrete
• Cement screeds

Why choose P 7?

• Ready to use
• Fast drying
• Helps improve adhesion before levelling.

Ardex P 51 – For Absorbent Subfloors

Ardex P 51 is a water-based acrylic primer developed for porous and absorbent substrates. It regulates the absorbency of the subfloor, helping levelling compounds cure consistently while reducing the risk of pinholes and rapid moisture loss.

Ideal for:

• Cement screeds
• Concrete
• Calcium sulphate screeds

Why choose P 51?

• Reduces substrate absorbency
• Improves bond strength
• Suitable before smoothing compounds.

Ardex P 4 – For Smooth & Dense Surfaces

Ardex P 4 is designed for difficult, smooth and dense substrates where additional adhesion is required.

Containing coloured sand, it creates a textured surface that helps levelling compounds achieve a strong mechanical bond.

Ideal for:

• Ceramic tiles
• Terrazzo
• Quarry tiles
• Existing epoxy coatings

Why choose P 4?

• Excellent adhesion
• Solvent free
• Creates a textured bonding surface.

Ardex P 82 – For Impervious Substrates

Ardex P 82 is a two-part synthetic resin primer developed for smooth and impervious substrates.

It provides a strong bonding bridge where conventional primers may not be suitable and is often used before applying smoothing compounds to dense or moisture-sensitive surfaces.

Ideal for:

• Steel
• Terrazzo
• Ceramic tiles
• Existing epoxy coatings
• Timber-based panels

Why choose P 82?

• Two-part system
• High bond strength
• Suitable for difficult substrates.

Ardex PU 30 – Moisture Barrier, Primer & Consolidator

Unlike the other primers in the Ardex range, PU 30 performs three important functions in one product.

It can be used as a primer, a moisture barrier on cement screeds and concrete floors with elevated residual moisture, and a substrate consolidator to strengthen absorbent surfaces before levelling or bonding. It is also suitable beneath Ardex reaction adhesives and can be used on a wide range of absorbent and non-absorbent substrates. It is supplied ready to use, is water- and solvent-free, and is reworkable after approximately one hour.

Why choose PU 30?

• Moisture barrier
• Strengthens weak substrates
• Ready to use
• Suitable beneath Ardex reaction adhesives.

Which Ardex Primer Is Right for You?

• Need a universal primer? Choose Ardex P 7.
• Preparing an absorbent screed or concrete floor? Choose Ardex P 51.
• Working over ceramic tiles or other smooth surfaces? Choose Ardex P 4.
• Priming dense or impervious substrates? Choose Ardex P 82.
• Need moisture protection and substrate consolidation? Choose Ardex PU 30.

Final Thoughts

Using the correct primer is one of the simplest ways to improve the performance of your flooring installation. Whether you're reducing the absorbency of a screed, improving adhesion to smooth surfaces or protecting against residual moisture, Ardex offers a primer designed for the task.

At Floormart, we stock the full range of Ardex primers, helping installers choose the right solution for every stage of subfloor preparation. If you're unsure which primer is best for your project, our team is on hand to help.