Description
Atlas Uni-Grunt 5 kg is the container bought for one wall rather than one job. Same deep-penetrating primer as the trade pack, same data sheet, same declared values — what changes is how much of it has to survive in the van until the next call-out. On an interior room, a gable, or a patched elevation waiting for render, this is the pack size the arithmetic points at.
What One Atlas Uni-Grunt 5 kg Container Primes
The manufacturer states two things about quantity, and they belong together. Average consumption is 0.05–0.2 kg/m², which is a property of the wall. The yield table is a property of the container and the dilution it is used at.
| Wall and layer above | Dilution | One 5 kg container |
|---|---|---|
| Weak, highly absorbent masonry | Undiluted | Up to 100 m² |
| Standard absorbency, screeds and plaster | 1:1 | Up to 200 m² |
| Standard absorbency, finishes and adhesives | 1:3 | Up to 400 m² |
Those are upper limits, reached where the wall sits at the 0.05 kg/m² end of the consumption band. At the thirsty end the same container runs 5 kg ÷ 0.2 kg/m² = 25 m², which is one gable of old brickwork and not much more. The honest way to order is to take 25 m² as the floor on an unknown substrate and treat everything above it as headroom. Placing an unfamiliar wall before ordering is what the guide to rendering on brick, block and painted walls is for.
Jobs This Pack Size Suits
- One elevation at a time — a gable, an extension flank, a garage wall, where even a thirsty substrate finishes inside the container.
- Interior work — plaster and masonry walls before paint or wallpaper, where the declared emission figure matters more than pack economics.
- Repairs and patched areas — the manufacturer's own claim is that the layer above gets uniform setting conditions across the whole surface, local repairs included, which is exactly the wall a small pack gets bought for.
- Reserve stock — held against the twelve-month shelf life rather than against next season.
That last point is the real argument for Atlas Uni-Grunt 5 kg alongside the trade container. Shelf life runs twelve months from the production date printed on the packaging, so a part-used 10 kg tub bought for a 30 m² wall is a saving that expires. Matching container to wall wastes less than matching container to habit.
Declared Values for the Primer
Every value in this table comes from the manufacturer's technical data sheet for Atlas Uni-Grunt, updated June 2025, and from no other source.
| Property | Declared value |
|---|---|
| Product type | Deep-penetrating primer |
| Binder base | Water dispersion of polymer resins |
| Emulsion density | Approx. 1.0 g/cm³ |
| Average consumption | 0.05–0.2 kg/m² |
| Substrate and air temperature | +5 °C to +30 °C |
| Next layer, Atlas adhesive mortars | After approx. 15 minutes |
| Next layer, paints and screeds | After approx. 2 hours |
| Surface after drying | Colourless and matt |
| VOC content | 1.92 g/l against 30 g/l permitted |
| Shelf life | 12 months from production date |
| Classification | Not a construction product |
The VOC line is the one that decides interior work. Maximum content is declared as 1.92 g/l against 30 g/l permitted under Cat. A/h/FW, and the primer is solvent-free, water-soluble while wet and colourless once dry, so it leaves no cast under a pale emulsion paint. The classification line matters to a specifier rather than an applicator: because the primer is not a construction product there is no declared performance and no DoP number attached to it.
Dilution and Application, Indoors and Out
The wall wants to be dry and clear of dust, dirt, oil, grease and wax, with loose layers taken off first. The primer is supplied ready to use and is not mixed with anything or thickened, so dilution is the only variable left on site:
- Weak and highly absorbent masonry — cement-lime plaster, aerated concrete, silicate brick, mixocrete screed — takes it undiluted, or twice at 1:1.
- Normal absorbency under a screed or plaster takes one coat at 1:1.
- Normal absorbency under finishes, paints, waterproofing or adhesives takes one coat at 1:3.
Lay Atlas Uni-Grunt 5 kg on thin and even with a roller, brush or sprayer and stop at saturation — puddles and streaks are a sign of too much, not of thoroughness. When the surface has dried, wet it and watch how quickly it takes the water in; a wall that still drinks gets primed again. Above it, an Atlas adhesive mortar can follow after roughly fifteen minutes, while painting, wallpapering and tiling wait the full drying time of roughly two hours. Both intervals are tied to temperature and humidity rather than to a clock. The preparation sequence ahead of priming sits in the substrate preparation guide.
Where Atlas Uni-Grunt 5 kg Is Not the Answer
Interior walls are where the manufacturer's two data sheets stop agreeing, so both are stated with their dates and the stricter one leads. The current sheet marks gypsum plaster, plasterboard, anhydrite screed and monolithic concrete as suitable for the standard primer. The earlier English sheet, dated August 2021, recommended Atlas Uni-Grunt Ultra on exactly those substrates. The newer document permits more; the older one permits less, and on gypsum, anhydrite and dense concrete the Ultra concentrate remains the safer specification. It is a different formulation, not a smaller tub.
Surfaces that cannot take anything in rule out a penetrating primer altogether:
- existing ceramic and stone cladding, and terrazzo;
- OSB board, stable linoleum and PVC;
- concrete varnish and oil-based paint coatings.
Those need a keyed film, and on the Renders World shelf that is Atlas Ultragrunt for critical substrates. Dried splashes come off with Atlas Szop 2000, wet ones with clean water.
Five Kilos or Ten
| Job | Container | What decides it |
|---|---|---|
| One wall, interior room, repair patch | Uni-Grunt 5 kg | Up to 100 m² undiluted |
| Whole elevations, EWI substrate priming | Uni-Grunt 10 kg container | Up to 200 m² undiluted |
The crossover is a date rather than a quantity: whichever container will be empty inside twelve months is the right one, which is why Renders World stocks Atlas Uni-Grunt 5 kg beside the trade pack. Render work adds a second layer to the decision, because priming is not keying. A thin-coat silicone or acrylic finish bonds to a quartz key coat above the consolidated substrate — that layer is Cerplast quartz top coat primer, and the two sit in very different consumption bands. The comparison is in the primer comparison for thin-coat render and the method in the quartz primer application guide. The rest of what Renders World stocks for substrate preparation sits on the primer shelf, and the finishes this work leads to are the thin-coat silicone topcoats from Renders World.
Pack Size, Gypsum and Storage
How much wall does one 5 kg container prime?
Up to 100 m² undiluted, up to 200 m² at 1:1 and up to 400 m² at 1:3, all upper limits from the manufacturer's yield table. Against the thirsty end of the 0.05–0.2 kg/m² band the same container covers 25 m².
Is this the same material as the 10 kg container?
Yes. Atlas Uni-Grunt 5 kg carries the same formulation, the same data sheet and the same declared values for density, consumption, drying intervals and emissions. Pack size is a quantity decision and nothing else.
Can it go on plasterboard and gypsum plaster?
The two data sheets answer differently:
- the sheet updated June 2025 marks gypsum plaster and plasterboard as suitable;
- the English sheet dated August 2021 pointed those substrates at Uni-Grunt Ultra.
Where the finish is a decorative paint on fresh gypsum the Ultra concentrate is the safer call, and the paint manufacturer's own priming instruction takes precedence over both.
Can render go directly onto the primed wall?
Treat the emulsion as substrate preparation and take the coat immediately beneath the finish from the render manufacturer's instruction, which for Atlas thin-coat systems is a quartz key coat.
How long does a part-used container keep?
Shelf life is twelve months from the production date printed on the packaging, and it runs from that date rather than from opening. Sizing the container to the wall is the practical way of staying inside it.
Technical Documentation