Description
Cerplast 15kg is the middle bucket in the Atlas Cerplast range, and the one most single-elevation jobs actually need. The material is identical to the trade tub: a ready-to-use mass of acrylic resins and quartz flour, which leaves a deliberately rough surface for the render to grip. Only the pack differs, and it is sized for one gable, one extension flank or one repair area rather than a whole house. The question this bucket answers is therefore a quantity question, which is why Renders World stocks it beside the trade size in the render primer range.
How Much Wall One Cerplast 15kg Bucket Primes
Two documents give two consumption figures. They are not in conflict — they describe different scopes, and knowing which one you are ordering against is the whole of the arithmetic.
The Atlas technical sheet gives an average of 0.3 kg/m² for the material. BBA Agrément Certificate 13/5018 gives 0.25 to 0.35 kg/m² for key coats inside the certified build-up. On a 15 kg bucket that divides three ways:
- One bucket covers 50 m² at 0.30 kg/m², the sheet's own average.
- One bucket covers 42.9 m² at 0.35 kg/m², the top of the certified band.
- One bucket covers 60 m² at 0.25 kg/m², the bottom of it.
Order a Cerplast 15kg against 42.9 m² and the margin sits with you rather than with the next delivery. A 40 m² gable takes one bucket with reveals to spare. Fifty-five square metres of elevation takes two buckets, and at that point the trade tub does the same wall from a single lid. Suction is what moves the real figure within that band, and the substrate matrix for brick, block and painted walls is the honest place to set expectations before the order goes in.
Which Bucket the Job Needs
| Job | Pack | Plan on |
|---|---|---|
| One elevation, extension flank, garage, repair | 15 kg | 42.9 m² |
| Whole house, terrace run, several elevations | 25 kg tub | 71.4 m² |
Nothing else divides the two. A Cerplast 15kg bucket carries the same declared figures, the same certificate entries and the same tinting as the trade tub — quantity and the number of lids are the entire difference. What the smaller pack gives you is this:
- One bucket, one elevation. 42.9 m² on the certified consumption band covers a gable, an extension flank or a garage without a part-used tub left standing in the store.
- The trade tub's figures at a quarter less material. Bond, drying time and working range are declared once, for the material, and apply to every pack size.
- A component named in a UK certificate. BBA Agrément Certificate 13/5018 lists Cerplast as a key coat inside the Atlas/Aval EPS and Roker MW insulation systems.
- Ready to use. No gauging vessel, no thinning and no mixing ratio — stir the Cerplast 15kg bucket and start.
What the Sheet Declares
| Property | Declared value |
|---|---|
| Composition | Acrylic resins and quartz flour, ready to use |
| Bond to concrete | At least 1.0 MPa |
| Density | Approx. 1.5 g/cm³ |
| Drying before rendering | 4 to 6 hours |
| Working temperature | +5 °C to +30 °C |
| Consumption, product scope | Approx. 0.3 kg/m² |
| Key coat coverage, system scope | 0.25 to 0.35 kg/m² |
| Application | Roller, brush or machine |
| Pack sizes | 5, 10, 15 and 25 kg buckets |
| Shelf life | 12 months from the date on the bucket |
The bond figure is printed twice in the same sheet — "min. 1.0 MPa" in the description, "> 1.0 MPa" in the data table. Both readings support the same practical statement, which is the one above.
Which Finishes It Is Allowed Under
The paperwork splits here, and the split decides which bucket belongs on a certified job. Three scopes, narrowest last:
- The technical sheets, Polish edition updated May 2025 and English edition July 2023, put Cerplast under Atlas thin coat renders described as mineral, acrylic, silicone and mosaic DEKO M.
- BBA Agrément Certificate 13/5018, EPS system, names it as the key coat for mineral, Atlas Acrylic Render and acrylic-silicone finishes, and routes silicone and silicone-silicate finishes to a different key coat named in the same sheet.
- The same certificate, Roker MW system, narrows it further still, to the mineral finish alone.
The difference is scope, not error: a product sheet says what the material can do, a certificate says what one tested assembly contains. On a certified build-up the certificate governs, because it permits less. The full sheet-by-sheet reading sits on the 25 kg product page.
One assembly figure from the certificate is resolvable and worth quoting: in the Roker MW system, the 7 mm build-up of Roker W-20 basecoat, a Cerplast key coat and the Cermit mineral finish is rated Use Category III for impact. The EPS sheet gives no equivalent, and the reason is the shape of its table rather than the product — the rows name the basecoat and the finish but not which key coat went with them. No reaction-to-fire class belongs to the primer on its own; those classifications describe complete build-ups of adhesive, board, basecoat, mesh, key coat and finish.
Getting the Wall Ready
The substrate has to be stable, seasoned, air-dry, even and clean — free of dust, dirt, lime, oil, grease, wax and residues of oil and emulsion paint. Seasoning times are all quoted for setting conditions of +20 °C and 50 % air humidity:
- New cement plasters from Atlas ready-mixed mortars, and traditional cement and cement-lime plasters: a minimum of 7 days, with moisture content at or below 4 %.
- Concrete: a minimum of 28 days, with structural moisture below 4 %.
- Reinforced layers in an Atlas insulation system: the time printed in the technical sheet of the adhesive that made the layer, which the primer's own sheet declines to restate.
- Interior paint coatings with good adhesion to the wall: no seasoning requirement.
Where the wall needs work before the Cerplast 15kg goes on, the sheet names the route rather than leaving it to judgement. Fill hollows and unevenness with ZW 330 or an Atlas plastering mortar, prime the repair with a ready-to-use emulsion — Atlas Uni-Grunt for general masonry, the NKP primer where absorption is low or uneven — and clear algae or fungal growth with Mykos Plus before anything else goes on. The full sequence is in the Renders World wall preparation method.
Then the key coat itself. Stir the Cerplast 15kg bucket immediately before use and again during the work, because the quartz settles in storage. Spread it evenly across the whole surface with a roller, a brush or by machine, working a full elevation in one pass so the suction ends up even. Leave it 4 to 6 hours to dry completely before the render or the cladding goes on. Do not thin it, thicken it or combine it with anything else — it is supplied at working consistency. Protect the primed face from direct sun, wind and rain both while you work and while the render dries. Clean tools with clean water straight after use, and take cured splashes off with Szop 2000. Roller choice and weather planning are covered in the quartz key coat application guide for EWI systems.
Colour and Tinting
A Cerplast 15kg bucket ships white, and white is what most jobs use, since the render above it carries the colour. Tinting is available in a mixer to the SAH Colours of Renders and Paints scheme, and the two current sheets do not agree on how many shades that is:
- 400 shades in the English sheet of July 2023 — the figure to quote and to specify against.
- 418 shades in the Polish sheet of May 2025.
- Seven shades dedicated to the Atlas DEKO M mosaic renders: white, brown, clinker, graphite, sand, grey and coffee.
Which of the seven belongs under a given DEKO M render is printed in that render's own technical sheet rather than in the primer's, so that sheet is where the pairing is settled.
What the Documents Do Not Settle
Three things are worth naming plainly rather than filling in.
- Frost and incompatible metals. A 2015 edition of the English data sheet warns that the material freezes below 0 °C and is then spent, that it should be kept below 30 °C, and that it should not meet aluminium, copper or their alloys. Neither current edition carries that section; both send those questions to the Safety Data Sheet. Treat the 2015 wording as the last written guidance on storage, and keep the bucket out of an unheated van in January either way.
- A break in the programme. Where the season closes before the render can go on, the reinforced layer may be left protected by the key coat alone until conditions allow the finish. No period is given for that in any edition, so it is a site judgement and not a figure.
- Classification of the material itself. No EN 15824 class, vapour class, water-absorption class or DoP number is declared for this product in any of its technical sheets. The performance statements that do exist belong to the systems it is a component of.
Renders World lists what the documents declare about Cerplast 15kg and marks the gaps where they declare nothing, which on a certified job is the difference between a specification that holds and one re-argued on site.
Coverage, Compatibility and Conditions
How many 15 kg buckets does one elevation take?
Divide the area by 42.9 m² and round up. That figure is 15 kg at 0.35 kg/m², the top of the band BBA Agrément Certificate 13/5018 gives for key coats, so it leaves the margin on your side. At the Atlas sheet's own 0.3 kg/m² average the same bucket reaches 50 m².
Can it go under a silicone render?
The current Atlas technical sheets list silicone among the thin coat renders it primes. Certificate 13/5018 does not: it routes silicone and silicone-silicate finishes to a different key coat and keeps Cerplast for mineral, acrylic and acrylic-silicone. On a certified build-up, follow the certificate; the primer comparison for thin coat systems sets out how the range divides by finish.
What conditions does it need on site?
Three, and an uneven drying rate is what the third one guards against:
- Mass, substrate and air between +5 °C and +30 °C.
- 4 to 6 hours of drying before the render goes on.
- Shelter from direct sun, wind and rain while you work and while the render dries.
Does the certificate cover the bucket or the wall?
The wall. Agrément Certificate 13/5018 is issued for the Atlas/Aval external wall insulation systems, and Cerplast appears inside it as one named component of an assembly. Quoting the certificate number together with the system it covers is what Building Control and warranty providers are looking for.
Technical Documentation for Atlas Cerplast
- Cerplast technical data sheet, Polish edition updated 2025-05-22 (PDF)
- Cerplast technical data sheet, English edition updated 2023-07-24 (PDF)
- BBA Agrément Certificate 13/5018, Product Sheet 1 — Atlas/Aval EPS system (PDF)
- BBA Agrément Certificate 13/5018, Product Sheet 2 — Atlas/Aval Roker MW system (PDF)