Description
Atlas Uni-Grunt Ultra 4 kg is a high-yield deep-penetrating concentrate priming emulsion for absorbent UK substrates, covering up to 280 m² (rendering, 1:6 dilution) or 360 m² (painting, 1:8 dilution) from a single container — the highest material economy in the render primer range. The polymer-dispersion concentrate carries a control pigment that tints the substrate during application for visible coverage confirmation, and consolidates bare masonry ahead of quartz topcoat primers and thin-coat silicone render systems on full-house facade jobs where material cost per square metre matters.
Where Atlas Uni-Grunt Ultra Performs Best — Large-Area UK Projects and Adjustable Dilution
Atlas Uni-Grunt Ultra solves the problem that limits standard ready-to-use primers on large UK facade jobs: material cost per square metre. The 4 kg concentrate dilutes to three task-specific ratios — 1:3 for screeds and self-levelling compounds (≈53 m²), 1:6 for renders, plasters, and tile adhesives (≈280 m²), and 1:8 for paint and wallpaper preparation (≈360 m²) — so one container handles every priming task on a building from basement floor to final exterior coat. The high polymer-dispersion content drives the emulsion deep into the pore structure of bare brick, blockwork, aerated concrete, and cured EWI basecoats, binding loose aggregate grains and reducing absorbency so the next coat dries at a controlled, uniform rate.
The integrated control pigment tints the substrate as the primer is applied, showing coverage progress in real time and disappearing under subsequent layers without affecting topcoat colour. Within the PRIMER-SUBSTRATE selection framework, Uni-Grunt Ultra sits as the consolidator that precedes a quartz grip coat (Cerplast or CT16) before thin-coat render application. The silicone render primer comparison guide sets out the full decision matrix; complete substrate-assessment and porosity-checking sequences are covered in the substrate preparation method guide.
Why Trade Specifiers Choose Atlas Uni-Grunt Ultra
- Highest Coverage Per Container in the Range: Up to 360 m² at the 1:8 dilution and 280 m² at the 1:6 dilution from a single 4 kg pack — the most cost-effective consolidation primer for full-house and multi-elevation programmes where material economy directly affects project margin.
- Visible Coverage Confirmation via Control Pigment: The integrated pigment tints the substrate during application so missed patches show immediately under good light, then disappears under subsequent layers without reducing topcoat covering power — a no-equipment QA pass on every elevation.
- Three Task-Specific Dilution Ratios: 1:3 for screeds and self-levelling compounds, 1:6 for renders and tile adhesives, 1:8 for paint preparation — one product replaces three different primer SKUs on jobs that span flooring, rendering, and decoration in the same building.
- 15-Minute Next-Coat Window on Standard Masonry: Plasters, adhesives, and render basecoats can follow just 15 minutes after priming on standard masonry, keeping tight UK programmes on schedule and reducing scaffold-hire days on multi-storey work.
- Deep Polymer Penetration for Substrate Reinforcement: The high polymer-dispersion content carries the emulsion into the pore structure and bonds loose aggregate from within, producing a consolidated layer that resists dusting and holds every subsequent coat firmly in place.
- Solvent-Free, Indoor and Outdoor: Water-based formulation with no hazardous classifications, certified for walls, floors, and ceilings on both interior and exterior substrates within a +5 °C to +30 °C working window covering the full UK rendering season.
- Compatible With Atlas ETICS System Sequence: Consolidates bare masonry before the quartz grip coat in Atlas certified facade build-ups, supporting BBA and ETA system warranty when followed by Atlas Cerplast and an Atlas thin-coat render.
Technical Specifications — Atlas Uni-Grunt Ultra Data Sheet Highlights
| Property | Value |
|---|---|
| Product Type | Deep-penetrating concentrate priming emulsion |
| Binder | Aqueous polymer resin dispersion (high polymer content) |
| Density | ~1.0 g/cm³ |
| Pack Size | 4 kg plastic container |
| Consumption | 0.022–0.075 kg/m² (varies with dilution and substrate) |
| Dilution — Screeds / Self-Levelling Floors | 1:3 with water (≈53 m² per 4 kg) |
| Dilution — Renders / Plasters / Tile Adhesives | 1:6 with water (≈280 m² per 4 kg) |
| Dilution — Painting / Wallpapering | 1:8 with water (≈360 m² per 4 kg) |
| Drying Time — Standard Masonry | ~15 minutes |
| Drying Time — Self-Levelling Floors | ~2 hours |
| Application Temperature | +5 °C to +30 °C (substrate and ambient) |
| Control Pigment | Yes — tints substrate to show coverage; disappears under topcoat |
| Solvent Content | None (solvent-free, water-based) |
| Application Method | Roller, brush, or airless spray |
| Use | Indoor and outdoor; walls, floors, and ceilings |
| Shelf Life | 12 months from production date (sealed, frost-free storage) |
| Storage Conditions | Sealed container, +5 °C to +25 °C; protect from frost and direct sunlight |
| Manufacturer | Atlas Sp. z o.o. |
How to Apply Atlas Uni-Grunt Ultra — Dilution Mixing, Substrate Prep, and Coverage Verification
Match the dilution ratio to the task before mixing: 1:3 with clean water for screeds and self-levelling compounds, 1:6 for renders and tile adhesives, 1:8 for paint and wallpaper preparation. Measure water by volume into a clean bucket first, then add the concentrate to the water (not the reverse), stirring continuously to prevent the polymer settling at the bottom and producing inconsistent concentration across the batch. Apply the diluted emulsion as a single even coat with a roller, brush, or airless sprayer between +5 °C and +30 °C on a clean, dry, structurally sound substrate free from dust, oil, and loose material.
Work methodically across the surface in overlapping passes — the control pigment shows untreated areas as a lighter colour, so a quick visual scan from scaffold level confirms full coverage before the next coat goes on. Complete each elevation in a single continuous session rather than stopping mid-wall, because a partially dried lap line creates a visible absorption difference that can show through the finished topcoat as a faint band. On aerated concrete blocks and other very high-suction substrates, the first pass absorbs almost instantly; a second coat after 15 minutes doubles the consolidation depth and gives the quartz primer a perfectly consistent base to grip.
Installation Notes — Atlas EWI System Sequence and Weather Planning
On a full Atlas ETICS build-up, Uni-Grunt Ultra (1:6 dilution) consolidates bare masonry before EPS or mineral wool boards bond with system adhesive; a cementitious basecoat with embedded fibreglass mesh forms the reinforcing layer; Atlas Cerplast deposits the quartz grip coat on the cured basecoat; and an Atlas silicone, acrylic-silicone, mineral, or mosaic topcoat completes the facade. Allow the full 15-minute drying window on standard masonry before the next coat; extend to 30 minutes on cool or humid UK days for the most reliable consolidation depth. Check substrate temperature with an infrared thermometer on shaded and north-facing elevations rather than relying on the air reading alone — surface temperature can sit several degrees below the ambient figure on cool mornings.
For self-levelling compounds and screeds at the 1:3 dilution, allow the full 2-hour drying window before pouring the screed; the higher polymer concentration needs the extra time to bond loose aggregate before taking the load of fresh compound. Check a 48-hour weather forecast before outdoor application to ensure no rain falls during the drying window — uncured primer washed from the wall by rain leaves the substrate inconsistently consolidated. Clean tools with water immediately after use; once the polymer dries on roller fibres or brush bristles, it bonds permanently. Store unused concentrate sealed and upright at +5 °C to +25 °C, protected from frost; frozen emulsion separates irreversibly.
Pro Tips From UK Installers Using Atlas Uni-Grunt Ultra
- Stick to the 1:6 ratio for rendering work: The weaker 1:8 mix is designed for paint preparation only — using it before render reduces consolidation depth below the threshold the quartz topcoat needs to bond reliably, so reserve 1:8 strictly for decoration prep.
- Water in first, concentrate second: Pour measured water into the bucket first, then add the concentrate while stirring; the reverse order lets polymer pool at the bottom and produces patchy concentration across the working batch.
- Second pass on aerated block at 15 minutes: Very high-suction aerated concrete absorbs the first coat almost instantly; a second pass at the standard 15-minute mark doubles the consolidation depth where the substrate would otherwise stay under-primed.
- Trust the pigment on multi-operative teams: On large elevations where several installers are priming simultaneously, a visual scan from scaffold level confirms every section has been covered before the quartz coat goes on, eliminating the callback risk of a missed strip showing through as a drying-speed difference in the finished render.
- Mix in batches that match the working window: Diluted emulsion stays workable for the day but loses its peak penetration after the first 4–6 hours; mixing the volume needed for each session rather than a full container at once delivers the deepest consolidation on every elevation.
Is Atlas Uni-Grunt Ultra Right for Your Project?
- Yes — for large-area absorbent substrate priming where material economy matters: Full domestic facades, multi-room interiors, commercial floors, and multi-elevation programmes where the per-square-metre cost from a 4 kg concentrate beats every ready-to-use alternative in the range.
- Prefer ready-to-use without on-site mixing? The Atlas Uni-Grunt 10 kg uses the same polymer-dispersion technology in a pre-mixed format that requires no water addition — slower per-square-metre coverage but faster to deploy on smaller jobs or sites where precise mixing is impractical.
- Working on smooth, non-absorbent surfaces? Deep-penetrating primers rely on substrate porosity to carry the polymer into the masonry; on terrazzo, ceramic tiles, OSB, smooth poured concrete, or steel, Atlas Ultragrunt 5 kg deposits coarse quartz aggregate onto the surface to create a physical mechanical key instead.
- Need a quartz grip coat for the EWI basecoat stage? Uni-Grunt Ultra consolidates the bare wall; Atlas Cerplast 25 kg provides the textured quartz key on the cured basecoat before the render topcoat — the two products work at different system stages and complement each other on the same build-up.
FAQ — Atlas Uni-Grunt Ultra Coverage, Dilution, and Compatibility
How much area does one 4 kg container cover?
Coverage depends on the dilution ratio matched to the task. At the 1:3 dilution for floor preparation before self-levelling compounds, one container covers approximately 53 m². At the 1:6 dilution for render, plaster, and adhesive preparation, coverage rises to approximately 280 m². At the 1:8 dilution for painting and wallpapering, one container stretches to approximately 360 m². On highly absorbent substrates such as old aerated concrete blocks, the first coat absorbs quickly and a second pass is recommended — which roughly halves the effective coverage per container, so ordering two containers for a 250 m² aerated-block facade at 1:6 dilution is a practical precaution.
Which dilution ratio should I use for rendering over EWI?
For priming bare masonry or a cured EWI basecoat before applying a quartz topcoat primer and then silicone render, the 1:6 dilution is the standard specification within Atlas certified facade systems. This ratio delivers enough polymer concentration to consolidate the substrate and regulate absorption, ensuring the quartz coat bonds to a stable, evenly absorbent surface that gives the finished topcoat a uniform colour and texture across the full elevation. Sticking to the 1:6 ratio for render preparation is a step worth getting right — the weaker 1:8 mix is designed for paint preparation only, where the demands on consolidation depth are lower.
Can Atlas Uni-Grunt Ultra be used outdoors in UK weather?
Uni-Grunt Ultra is certified for both indoor and outdoor use on walls, floors, and ceilings, with a +5 °C to +30 °C application window covering the standard UK rendering season. Apply in stable, dry conditions and confirm the substrate temperature with an infrared thermometer rather than relying on the air reading alone — north-facing masonry can sit several degrees below the ambient temperature, particularly in spring and autumn when mornings are cool. Checking a 48-hour weather forecast before outdoor application avoids the risk of rain washing uncured primer from the wall.
What is the difference between Atlas Uni-Grunt Ultra and standard Atlas Uni-Grunt?
Both products are deep-penetrating consolidation primers based on aqueous polymer-resin dispersion, but Uni-Grunt Ultra is a concentrate that must be diluted with water before use, while standard Uni-Grunt is supplied ready to use (or dilutable at 1:1 or 1:3). The concentrate format gives Uni-Grunt Ultra a significantly higher yield per container — up to 360 m² from a single 4 kg pack compared to approximately 100 m² from a 10 kg pack of standard Uni-Grunt at full-strength application. The Ultra also includes a control pigment that tints the substrate during application, making coverage progress visible at a glance — a feature the standard version does not offer. For large projects where material economy matters most, the Ultra concentrate is the more cost-effective choice; for smaller jobs or quick single-room preparation, the ready-to-use Uni-Grunt saves the mixing step. The full primer selection across pack formats is covered in the primer selection guide.
Is Atlas Uni-Grunt Ultra the same as Atlas Ultragrunt?
The two products have similar names but solve opposite substrate problems. Atlas Uni-Grunt Ultra is a deep-penetrating liquid concentrate that soaks into porous, dusty, or high-suction masonry to consolidate the pore structure and regulate absorption. Atlas Ultragrunt is a quartz-aggregate priming mass for the opposite case — smooth, non-absorbent surfaces such as terrazzo, ceramic tiles, OSB, or steel, where there is no porosity for a liquid primer to exploit, so a coarse aggregate is deposited onto the surface to create a mechanical key. On mixed-substrate projects with both porous and non-absorbent areas, both products may be needed to give the entire wall a consistent bonding surface before the topcoat.
Is Atlas Uni-Grunt Ultra safe to use on occupied buildings?
Uni-Grunt Ultra is a water-based, solvent-free formulation that produces minimal odour during application and releases no harmful fumes during curing, so it suits work on occupied homes, schools, and care buildings without specialist ventilation or protective equipment beyond standard construction site practice. Once fully dried, the cured primer film is inert and vapour-permeable — walls continue to breathe naturally rather than trapping moisture — and leftover hardened residue disposes of as standard construction waste without specialist handling.
Technical Documentation — Atlas Uni-Grunt Ultra TDS and Manufacturer Resources