Description
Unlike deep-penetrating primers that rely on porosity to grip, Atlas Ultragrunt is a heavy-duty quartz-aggregate priming mass built for the surfaces that have none — terrazzo, ceramic tiles, smooth poured concrete, OSB, and steel — depositing a sandpaper-textured film that develops ≥1.0 MPa adhesion where a liquid primer would simply slide off.
Where Atlas Ultragrunt Performs Best — Critical UK Substrates and the Grip-Coat Sequence
Atlas Ultragrunt is a ready-to-use polymer-resin priming mass loaded with coarse quartz aggregate, formulated to build a mechanical key on smooth, sealed, and non-absorbent surfaces that defeat a conventional primer. On overcoating work where the existing finish is sound but slippery — a tiled splashback being extended, a smooth concrete stairwell taking a decorative render, a terrazzo lobby being levelled for new flooring — it removes the guesswork about whether the next coat will hold. Sitting in the Renders World render primer range, the 5 kg pack covers roughly 16.7 m² at 0.3 kg/m² and reaches ≥1.0 MPa on concrete, terrazzo, and ceramic tiles where penetrating primers pool without bonding.
Ultragrunt is certified for the critical substrate types most likely to defeat an ordinary primer: poured concrete, terrazzo, ceramic tiles, OSB boards, steel, ferroconcrete, anhydrite screeds, gypsum-fibre boards, and stable plastic flooring, indoors and outdoors, vertical and horizontal. The distinction that decides the job is porosity — where the wall can soak, a consolidator wins; where it cannot, only an aggregate grip coat works. The primer selection guide for UK render systems sets out the full decision matrix, and the substrate preparation method guide covers substrate assessment and porosity testing.
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 key that holds permanently on zero-suction substrates where ordinary primers pool without gripping.
- OSB 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 board rather than at the primer interface — the practical proof that timber-frame and panel substrates carry the load.
- Four-hour single-day schedule: A drying window of about 4 hours at 20 °C and 50–60 % RH keeps the next coat on the same day, cutting scaffold-hire days on multi-storey work and tightening retrofit programmes.
- Ready to use without dilution: The container goes straight onto the substrate with no mixing or additives — diluting reduces aggregate concentration and weakens the mechanical key, so it works precisely as supplied.
- Extended temperature tolerance (+5 °C to +35 °C): An extra 5 °C of headroom at the top keeps the product within specification on south-facing summer scaffolds and during UK heatwave conditions.
- Indoor and outdoor, vertical and horizontal: Certified across walls, floors, and ceilings on interior and exterior substrates, so one product covers external facades, internal feature walls, and floor prep on the same project.
- Verified tactile confirmation: The cured film feels distinctly gritty and sandpaper-like, giving an instant on-site check that the quartz aggregate has bedded in before the next coat.
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 (15 kg also available) |
| 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 brush; 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) |
| Manufacturer | Atlas Sp. z o.o. |
How to Apply Atlas Ultragrunt — Substrate Prep, Roller Technique, and Bond Verification
Atlas Ultragrunt reaches full specification on a clean, dry, dust-free substrate free from oil, grease, wax, and any loose or poorly bonded layers, applied between +5 °C and +35 °C. Stir the container 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 so every quartz grain transfers into the surface rather than sitting loosely on top. On vertical surfaces, work from the bottom upward to catch any drips within the wet film. Never dilute or mix with other materials, because reducing aggregate concentration weakens the mechanical key that gives Ultragrunt its grip.
Substrate-specific preparation matters more on critical surfaces than on masonry. Terrazzo needs degreasing and removal of any paste or sealer residue so the quartz bonds to exposed stone. Ceramic tiles need cleaning to a sound glaze, with hollow or loose tiles replaced before priming. OSB needs a vacuum pass to clear sanding dust, and steel needs a wire-brush pass and solvent wipe to remove rust and mill scale, since Ultragrunt bonds to clean metal but cannot bridge corrosion. After 4 hours at 20 °C, run a palm across the film: a gritty, coarse feel confirms the aggregate has bedded in, while any smooth or glossy patch signals contamination that should be sanded, wiped, and re-coated. The full step-by-step technique sits in the substrate preparation method guide.
Installation Notes — System Sequences, Weather Planning, and Special Substrates
For self-levelling compounds and screeds on terrazzo, extend the wait from the standard 4 hours to 24 hours before pouring, so the polymer matrix reaches maximum bond strength under the load of fresh compound. Beneath thin-coat render on smooth concrete, sealed masonry, or existing tiles, the 4-hour window applies, with a full overnight cure on cool or humid UK days giving the topcoat its best foundation. For tile adhesive on OSB or steel, the 4-hour window holds provided the substrate stays within temperature throughout drying. Verify with an infrared thermometer that the substrate sits between +5 °C and +35 °C at application — sun-heated south-facing walls can exceed the upper limit in summer, so shaded-side or early-morning work gives the most stable drying window.
On a render build-up over a non-absorbent wall, Ultragrunt takes the role a conventional quartz primer fills on porous masonry: it establishes the grip coat, and an Atlas thin-coat silicone render then finishes the surface. Check a 48-hour forecast so no rain falls during the 4-hour external curing window. Clean rollers and brushes with water immediately after use, before resin and aggregate bond permanently to the fibres. Store sealed and upright at +5 °C to +25 °C — frozen primer separates irreversibly and cannot be recovered by thawing.
Pro Tips From UK Installers Using Atlas Ultragrunt
These are the working habits UK renderers rely on to get a permanent grip on the hardest substrates — the reward is a bond that holds where a standard primer would have failed.
- Sandpaper-test the cured film: Run a palm across the dried coat — a gritty, coarse feel confirms the aggregate has bedded in, while any smooth or glossy patch signals contamination that needs re-coating before the next layer.
- Match roller pile to orientation: Short-nap on floors for tight aggregate transfer, medium-nap 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, so a couple of pounds of degreasing wipes per panel protects the full 1.0 MPa bond potential on metal.
- Work the cooler part of the day on south-facing walls: Direct sun can skin the surface before the aggregate beds in, so early morning or late afternoon keeps the whole drying period at a stable temperature.
- Order one extra container per 100 m² of variable substrate: Consumption rises 10–15 % on rougher surfaces such as non-ground OSB or aged concrete, so a spare prevents a mid-job shortfall on mixed elevations.
How Atlas Ultragrunt Compares to Sibling Primers
Ultragrunt is the critical-substrate specialist in the primer range, so the honest comparison is against the products you would choose instead once the wall turns out to be porous or a standard basecoat. The table maps each primer to the substrate it suits, so the right choice follows from the surface in front of you.
| Variant | Key Spec | When to Choose |
|---|---|---|
| Atlas Ultragrunt 5 kg | Quartz grip coat · ≥1.0 MPa · ≈16.7 m² | Smooth, sealed, non-absorbent surfaces |
| Atlas Uni-Grunt 10 kg | Deep-penetrating liquid · ~100 m² | Porous, dusty, high-suction masonry |
| Atlas Cerplast 25 kg | BBA quartz grip coat · ~75 m² | Cured EWI basecoats in certified systems |
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 plastics where standard primers slide off; the heavy-duty quartz aggregate builds the coarse bonding surface that holds render, adhesive, and screed permanently.
- Working on overhead or ceiling surfaces where dripping is a concern? The Atlas NKP Primer 5 kg is a no-drip gel that holds on the roller during soffit work — the pick on conventional absorbent substrates where Ultragrunt's aggregate mechanism is not needed.
- Substrate porous and dusty rather than smooth? A deep-penetrating consolidator such as Atlas Uni-Grunt 10 kg soaks into the pore structure to stabilise masonry and even out drying, where Ultragrunt's surface grip coat would be absorbed away by a high-suction wall.
- Priming a normal-absorption EWI basecoat before render? The Atlas-certified quartz primer for that stage is Atlas Cerplast 25 kg, sitting within BBA Certificate 13/5018 for cured basecoats rather than the heavy-duty critical-substrate case.
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 0.3 kg/m² rate. On very smooth substrates such as polished terrazzo or glazed tiles, consumption stays close to that figure because the surface does not absorb product. On rougher surfaces with open texture — non-ground OSB or aged concrete — consumption rises 10–15 % as the mass fills micro-pores, so ordering an extra container per 100 m² of variable substrate is a practical precaution against a mid-job shortfall.
Can Atlas Ultragrunt be used outdoors in the UK?
Ultragrunt is certified for indoor and outdoor use on horizontal and vertical surfaces, with a +5 °C to +35 °C window covering UK site conditions from spring through autumn. The wider upper limit of +35 °C, against +25 °C or +30 °C for many standard primers, keeps the product within specification on south-facing elevations during summer heatwaves. Applying in the cooler part of the day and checking substrate temperature with an infrared thermometer gives the most reliable film formation on exposed facades.
Is Atlas Ultragrunt suitable 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 sit beneath a thin-coat render, it creates the mechanical key the render needs for permanent adhesion. On standard EWI basecoats with normal absorption, the Atlas-certified system specifies Cerplast instead, because the basecoat is already textured enough for a conventional grip coat. Keeping the primer within the same certified system as the render protects the manufacturer warranty and supports documented BBA compliance for Building Control sign-off.
What is the difference between Atlas Ultragrunt and Atlas Uni-Grunt?
They solve opposite substrate problems. Atlas Uni-Grunt is a deep-penetrating liquid consolidator for porous, dusty, or high-suction surfaces, soaking into 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 physical grip on smooth, sealed, or non-absorbent surfaces where there is no porosity for a liquid to exploit. On renovation projects where both substrate types appear on one elevation, both may be needed — Uni-Grunt on absorbent areas, Ultragrunt on smooth ones — so the whole wall reaches a consistent bonding surface.
How reliable is the bond on OSB and timber-frame panels?
Verified adhesion on OSB exceeds 0.8 MPa, with failure occurring inside the board rather than at the primer interface — meaning the bond is stronger than the OSB itself, so a render or tile system holds until the board would fail structurally. Vacuum the sanding dust before priming so the aggregate keys directly into the timber surface. For rendered timber-frame facades this makes Ultragrunt a dependable grip coat over the sheathing board, provided the wider build-up manages moisture and ventilation correctly.
What is the shelf life and storage requirement?
Atlas Ultragrunt carries a 12-month shelf life from production date, stored sealed and upright above +5 °C and below +25 °C, away from frost and direct sun. Frozen primer cannot be recovered by thawing, as the polymer resin and quartz aggregate separate irreversibly, so winter storage on unheated sites needs a frost-protected arrangement above +5 °C.
Technical Documentation — Atlas Ultragrunt TDS and Manufacturer Resources