Description
Roberts R48 Universal Primer is the primer referenced throughout the Roberts and RLA product range for preparing both porous and non-porous substrates ahead of adhesive or levelling compound application. Being rapid drying, solvent-free and low VOC makes it practical for a busy job site where waiting on a slower primer would hold up the rest of the installation.
Its dilution rate genuinely changes with the substrate: standard concrete gets a 1:2 primer-to-water mix, very absorbent concrete may need a second coat at 1:3, while non-porous surfaces like burnished concrete or glazed tile get an undiluted, neat coat instead. Getting that distinction right matters — too weak a mix under-primes a porous slab, while applying diluted primer to a non-porous surface won’t build the tack-free film subsequent products need to bond to.
Being referenced as the recommended primer across the entire Roberts and RLA adhesive range gives R48 a genuine role as a system-wide compatibility choice, rather than being tied to just one adhesive product — a real advantage on jobs using multiple Roberts or RLA products where a single, consistent primer simplifies both purchasing and application. Its different dilution rates for porous versus non-porous substrates reflect that those two surface types need meaningfully different primer strength to achieve a reliable bond.
Technical Specifications
| Composition | Water-based acrylic, solvent-free, low VOC |
|---|---|
| Dilution (standard porous concrete) | 1 part primer : 2 parts water |
| Dilution (very absorbent concrete, 2nd coat) | 1 part primer : 3 parts water |
| Application (non-porous) | Neat/undiluted |
| Cure time (porous) | 30 minutes |
| Cure time (non-porous, to tack-free film) | Approx. 1 hour at 23°C |
| Coverage | Approximately 5-10m² per litre |
| Minimum subfloor temperature | 10°C |
Where to Use
- Porous substrates such as standard and absorbent concrete
- Non-porous substrates including ceramic tiles and painted (water-based only) surfaces
- Ahead of cement-based ceramic tile adhesives and levelling compounds
How to Apply
- Assess the substrate — determine whether it is porous or non-porous.
- Dilute correctly — 1:2 for standard concrete, 1:3 for a second coat on very absorbent concrete, or neat for non-porous surfaces.
- Apply by roller or brush — ensure the entire area is completely primed.
- Allow to cure — 30 minutes for porous substrates, or approximately 1 hour to a tack-free clear film on non-porous surfaces.
- Apply the adhesive or levelling compound — once the primer has fully cured.
Important Notes
- Do not apply on high-gloss ceramic tiles without light grinding or sanding first to enhance adhesion.
- For subfloors with high moisture levels, an RLA Moisture Barrier is recommended instead — contact RLA Technical for guidance.
- Mix primer and water thoroughly before use.
