Description
Atlas Ultragrunt 5 kg is a heavy-duty quartz-aggregate priming mass for non-absorbent and low-suction substrates — terrazzo, ceramic tiles, smooth poured concrete, OSB boards, and steel — delivering ≥1.0 MPa adhesion where standard penetrating primers slide off without gripping. Stocked in the wider render primer range, this 5 kg pack covers approximately 16.7 m² at 0.3 kg/m² and prepares zero-suction surfaces for thin-coat silicone render systems, tile adhesives, and self-levelling compounds.
Where Atlas Ultragrunt Performs Best — Critical UK Substrates and Use Cases
On overcoating projects where the existing finish is sound but slippery — well-bonded ceramic tile splashbacks being extended, smooth concrete stairwell walls getting a decorative render, or terrazzo lobbies being levelled for new flooring — Atlas Ultragrunt is the product that eliminates the guesswork about whether the next coat will hold. The polymer-resin binder loaded with coarse quartz aggregate deposits a sandpaper-textured film that holds physically onto smooth, sealed, or non-absorbent surfaces, creating the mechanical key that standard penetrating primers cannot form on substrates with no porosity to soak into.
Ultragrunt is certified for the 16 critical substrate types most likely to defeat a conventional primer: poured concrete, terrazzo, ceramic tiles, OSB boards, steel, ferroconcrete, anhydrite screeds, gypsum-fibre boards, stable plastic flooring, and similar low-suction surfaces, indoors and outdoors, on both vertical and horizontal applications. For a side-by-side view of where each primer in the Atlas range fits, the silicone render primer comparison guide sets out the full decision matrix; complete substrate-assessment and preparation sequences are covered in the substrate preparation method guide.
Why Trade Specifiers Choose Atlas Ultragrunt
- Reliable Bond on Difficult Surfaces (≥1.0 MPa on Concrete, Terrazzo, Ceramic Tiles): The polymer-resin binder loaded with selected quartz aggregate creates a physical mechanical key that holds permanently on zero-suction substrates where ordinary primers simply pool without gripping.
- OSB Board Adhesion Above 0.8 MPa (Rupture Within the Board, Not the Bond Line): Verified bond strength on OSB exceeds 0.8 MPa with failure occurring inside the OSB substrate rather than at the primer interface — the practical proof that timber-frame and panel substrates carry the load reliably.
- Four-Hour Single-Day Schedule: A drying window of approximately 4 hours at 20 °C and 50–60 % RH keeps the next coat application on the same day, reducing scaffolding hire on multi-storey jobs and tightening the build programme on retrofit projects.
- Ready-to-Use Without Dilution: The container goes straight onto the substrate with no mixing, no water ratios, and no other additives — diluting reduces aggregate concentration and weakens the mechanical key, so the formulation works precisely as supplied.
- Extended Temperature Tolerance (+5 °C to +35 °C): An extra 5 °C of headroom at the top end versus standard +30 °C primers keeps the product within specification on south-facing summer scaffolds and during UK heatwave conditions.
- Indoor and Outdoor, Vertical and Horizontal: Certified for use across walls, floors, and ceilings on both interior and exterior substrates — one product covers external facades, internal feature walls, and floor preparation within the same project.
- Verified Tactile Confirmation: The cured film feels distinctly gritty and sandpaper-like to the touch, providing an instant on-site QA check that the quartz aggregate has bedded into the surface before the next coat goes on.
Technical Specifications — Atlas Ultragrunt Data Sheet Highlights
| Property | Value |
|---|---|
| Product Type | Quartz-aggregate priming mass (ready-to-use) |
| Binder | Polymer resin with selected quartz aggregate |
| Density | ~1.5 g/cm³ |
| Pack Size | 5 kg plastic container |
| Coverage Rate | ~0.3 kg/m² (≈16.7 m² per 5 kg) |
| Drying Time (Next Coat) | ~4 hours at 20 °C / 50–60 % RH |
| Application Temperature | +5 °C to +35 °C (substrate and ambient) |
| Adhesion to Concrete | >1.0 MPa |
| Adhesion to Terrazzo | >1.0 MPa |
| Adhesion to Ceramic Tiles | >1.0 MPa |
| Adhesion to OSB Boards | >0.8 MPa (rupture within OSB substrate) |
| Application Method | Roller or paintbrush; single even coat |
| Dilution | Ready to use; do not dilute or mix with other materials |
| Use | Indoor and outdoor; horizontal and vertical surfaces |
| 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 Ultragrunt — Substrate Prep, Roller Technique, and Bond Verification
Atlas Ultragrunt performs at full specification on a clean, dry, dust-free substrate free from oils, grease, wax, and any loose or poorly bonded layers between +5 °C and +35 °C. Stir the container thoroughly with a low-speed paddle for 2–3 minutes before use to redistribute settled quartz aggregate, then apply a single even coat with a medium-nap roller on walls or a short-nap roller on floors, pressing firmly to ensure every quartz grain transfers into the substrate rather than sitting loosely on top. On vertical surfaces, start at the bottom and work upward to catch any drips within the wet film. The product must not be diluted or mixed with any other material — reducing aggregate concentration weakens the mechanical key that gives Ultragrunt its grip.
Substrate-specific preparation matters more on critical surfaces than on conventional masonry. Terrazzo needs degreasing and removal of any paste or impregnating sealer residue so the quartz particles bond directly to the exposed stone. Ceramic tiles need cleaning to expose a sound glaze; loose or hollow tiles must be removed and replaced before priming. OSB boards need a vacuum pass to remove sanding dust. Steel substrates need a wire-brush pass followed by a solvent wipe to remove rust and mill scale, because Ultragrunt bonds to clean metal but cannot bridge corrosion. After 4 hours at 20 °C, run your palm across the cured film: it should feel distinctly gritty and coarse like fine sandpaper. If any area feels smooth or glossy, that section was likely contaminated — sand lightly, wipe clean, and re-coat before proceeding to the next layer.
Installation Notes — System Sequences, Weather Planning, and Special Substrates
For self-levelling compounds and screeds on terrazzo, the manufacturer recommends extending the wait time from the standard 4 hours to 24 hours before pouring the screed — the longer film-formation window gives the polymer matrix maximum bond strength under the load of a fresh compound. Beneath thin-coat render systems on smooth concrete, sealed masonry, or existing tiles, the standard 4-hour drying window applies; allow a full overnight cure on cool or humid UK days to give the topcoat the best foundation. For tile adhesive on OSB or steel, the 4-hour window applies provided the substrate stays within the temperature range throughout drying. Verify with an infrared thermometer that the substrate sits between +5 °C and +35 °C at the point of application — sun-heated south-facing walls can sit above the upper limit in summer, so shaded-side or early-morning application gives the most stable drying window.
Check a 48-hour weather forecast to confirm no rain falls during the 4-hour curing window on external work. Clean rollers and brushes with water immediately after use; once cured, the resin and aggregate bond permanently to roller fibres and brush bristles. Store unused product sealed and upright in the original container at +5 °C to +25 °C, protected from frost — frozen primer cannot be recovered by thawing because the resin and aggregate separate irreversibly.
Pro Tips From UK Installers Using Atlas Ultragrunt
- Sandpaper-test the cured film: Run your palm across the dried coat — a gritty, coarse feel confirms the quartz aggregate has bedded in; any smooth or glossy patch signals contamination and needs re-coating before the next layer.
- Match roller pile to orientation: Use a short-nap roller on floor substrates for tight aggregate transfer, and a medium-nap roller on walls and ceilings to carry enough product without dripping.
- Prime steel only after wire-brush and solvent wipe: Ultragrunt cannot bridge rust or mill scale; the £1–2 of degreasing wipes per panel protects the full 1.0 MPa bond potential on metal substrates.
- Apply in the cooler part of the day on south-facing walls: Direct solar exposure can skin the primer surface before the quartz aggregate has bedded in — early morning or late afternoon ensures the entire drying period proceeds at a stable temperature.
- Order one extra container per 100 m² of variable substrate: Consumption rises by 10–15 % on rougher surfaces such as non-ground OSB or aged concrete, so the spare container prevents a mid-job shortfall on mixed elevations.
Is Atlas Ultragrunt Right for Your Project?
- Yes — for smooth, non-absorbent, or low-suction substrates: Terrazzo, ceramic tiles, poured concrete, OSB, steel, and stable plastic surfaces where standard primers slide off or fail to grip; the heavy-duty quartz aggregate creates the coarse bonding surface that holds render, adhesive, and screed permanently in place.
- Working on overhead or ceiling surfaces where dripping is a concern? The Atlas NKP Primer 5 kg is a no-drip colloidal gel that holds on the roller during soffit and overhead application — the practical choice on conventional absorbent substrates where Ultragrunt's aggregate-grip mechanism is not needed.
- Substrate is porous and dusty rather than smooth? A deep-penetrating consolidator such as Atlas Uni-Grunt 10 kg soaks into the pore structure to stabilise the masonry and even out drying, where Ultragrunt deposits a surface grip coat that high-suction walls simply absorb away.
- Working on a normal-absorption EWI basecoat before render? The Atlas-certified quartz primer for that stage is Atlas Cerplast 25 kg, which sits within BBA Certificate 13/5018 and provides the conventional grip coat for cured basecoats rather than the heavy-duty critical-substrate solution.
FAQ — Atlas Ultragrunt Coverage, Compatibility, and Critical Substrates
How much area does the 5 kg container cover?
One 5 kg container covers approximately 16.7 m² at the manufacturer's stated consumption rate of 0.3 kg/m². On very smooth substrates such as polished terrazzo or glazed tiles, consumption stays close to this figure because the surface does not absorb product. On rougher surfaces with open texture — non-ground OSB or aged concrete — consumption can rise by 10–15 % as the mass fills micro-pores in the surface, so ordering an extra container per 100 m² of variable substrate is a practical precaution that prevents a mid-job shortfall.
Can Atlas Ultragrunt be used outdoors in the UK?
Ultragrunt is certified for both indoor and outdoor use on horizontal and vertical surfaces, and its +5 °C to +35 °C application window covers the full range of UK site conditions from spring through autumn. The wider upper limit of +35 °C (compared to +25 °C or +30 °C for many standard primers) keeps the product within specification even on south-facing elevations during summer heatwaves. Applying in the cooler part of the day and checking the substrate temperature with an infrared thermometer ensures optimal film formation on exposed facades.
Is Atlas Ultragrunt suitable for use before silicone render application?
Ultragrunt is designed for substrates where standard quartz primers fail to bond — smooth concrete, tiles, OSB, and similar non-absorbent surfaces. When those surfaces sit beneath a thin-coat render system, Ultragrunt creates the mechanical key the render needs for permanent adhesion. On standard EWI basecoats with normal absorption, the Atlas-certified system specifies Cerplast quartz primer instead, because the basecoat is already textured enough to accept a conventional grip coat. Keeping the primer within the same certified system as the render protects the manufacturer warranty and provides documented BBA compliance for Building Control sign-off — the full system selection is covered in the primer selection guide.
What is the difference between Atlas Ultragrunt and Atlas Uni-Grunt?
The two products solve opposite substrate problems. Atlas Uni-Grunt is a deep-penetrating liquid consolidator for porous, dusty, or high-suction surfaces — it soaks into the masonry to bind loose particles and regulate absorption so the next coat dries evenly. Atlas Ultragrunt stays on the surface and deposits coarse quartz aggregate to create a physical grip on smooth, sealed, or non-absorbent surfaces where there is no porosity for a liquid primer to exploit. On renovation projects where different substrates appear on the same elevation, both products may be needed — Uni-Grunt on absorbent areas and Ultragrunt on smooth ones — so the entire wall reaches a consistent bonding surface before the topcoat goes on.
Is Atlas Ultragrunt safe to use on occupied buildings?
Ultragrunt 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 extraction or protective equipment. The product contains no volatile organic compounds above standard construction thresholds, and once fully dried the cured film is inert — leftover hardened primer disposes of as standard construction waste without specialist handling. For indoor projects in kitchens, bathrooms, and utility rooms, standard domestic ventilation through an open window during application is sufficient.
What is the shelf life and storage requirement?
Atlas Ultragrunt carries a 12-month shelf life from production date when stored sealed and upright in the original container at temperatures above +5 °C and below +25 °C, protected from frost and direct sunlight. Frozen primer cannot be recovered by thawing — the polymer resin and quartz aggregate separate irreversibly — so winter storage on unheated sites or in vans overnight needs a frost-protected arrangement above +5 °C.
Technical Documentation — Atlas Ultragrunt TDS and Manufacturer Resources