Description
Atlas Cerplast sits at the key-coat stage of a rendered facade, between the cured basecoat and the decorative finish, and it is the largest bucket in the Renders World exterior render primers range. Everything specified below is read from the manufacturer data sheet and from both product sheets of BBA Agrément Certificate 13/5018, so the scope of each figure travels with it.
Where Atlas Cerplast Performs Best on UK Facades
Atlas Cerplast quartz top coat primer white 25kg is the acrylic and quartz key coat named in BBA Agrément Certificate 13/5018, bonding to concrete at a minimum 1.0 MPa and drying in four to six hours before rendering. That bond figure is a product-level value from the data sheet, and it is the reason the coat earns its place rather than being an optional extra.
Supplied as a ready-to-use mass, it must not be thinned, thickened or mixed with other materials — stirring to a uniform consistency immediately before use is the only preparation the sheet permits. The quartz powder in the acrylic binder leaves a deliberately rough film, which is what the wet render keys into.
- Concrete, once the wall has cured for at least 28 days.
- Traditional plasters on brick, ceramic, cellular or silicate blocks and hollow blocks.
- Plasterboard, for internal decorative render work.
- Thermal insulation systems with polystyrene, XPS and mineral wool.
Where a job mixes two or three of those in one elevation, the suction differences are what govern the result, and the substrate matrix for brick, block and painted walls sets out how each behaves before priming starts.
Why Specifiers Choose the White Quartz Top Coat Primer
The case for this bucket is documentary as much as technical: every line below is traceable to a sheet a specifier can hand to a warranty provider.
- A bond figure you can write into a spec: minimum 1.0 MPa to concrete, stated in the data sheet's technical data table as a property of the priming mass itself.
- Two consumption figures, both usable: the sheet gives an average of 0.3 kg/m², while BBA 13/5018 applies key coats at 0.25 to 0.35 kg/m² inside the certified build-up — order against the higher rate and the elevation never runs short.
- A named component, not an approximate match: Atlas Cerplast (Aval KT 16) appears by name in the key coats list of both the EPS and the Roker MW product sheets of BBA 13/5018.
- Same-day sequencing: 4 to 6 hours drying between +5 °C and +30 °C means priming in the morning and rendering the same afternoon on a settled UK day.
- Cover if the programme slips: the dried film forms a temporary protective layer for an unrendered facade, which the sheet puts at within half a year.
- Colour where it matters: the white base takes SAH tinting, and the three DEKO M-matched colours — brown, clinker and graphite — are supplied in the 15 kg and 25 kg packs only.
Technical Specification and What the Certificate Actually Covers
| Property | Documented value |
|---|---|
| Composition | Acrylic resins and quartz powder |
| Density, ready to use | Approx. 1.5 g/cm³ |
| Bonding to concrete | Minimum 1.0 MPa |
| Consumption, data sheet average | Approx. 0.3 kg/m² |
| Key coat coverage, BBA 13/5018 | 0.25–0.35 kg/m², system scope |
| Drying before rendering | 4–6 hours |
| Working temperature | +5 °C to +30 °C |
| Application | Roller, brush or machine |
| Pack sizes | 5, 10, 15 and 25 kg buckets |
| Shelf life | 12 months from production date |
| Storage limits | Below +30 °C, never frozen |
| System documents | BBA 13/5018, ETA 06/0081, NSAI 10/0347 |
BBA Agrément Certificate 13/5018 is a system certificate, issued for the Atlas/Aval External Wall Insulation System in two product sheets — the EPS system and the Roker MW system — and Cerplast is listed within them as one component. A bucket of primer is therefore a certified component of a tested assembly, which is a stronger and more defensible statement than calling the product itself certified.
For the same reason this page publishes no reaction-to-fire class and no impact Use Category. Both belong to a complete build-up of named adhesive, board, basecoat, mesh, key coat and finish, and lifting either onto a primer would misdescribe what was tested.
How to Apply Cerplast — Preparation, Quantity and Drying
Order on the certified upper rate rather than the average and the arithmetic stays comfortable: 25 kg ÷ 0.35 kg/m² = 71 m² per bucket, against 25 kg ÷ 0.30 kg/m² = 83 m² at the sheet's average consumption. A 100 m² elevation then reads 100 ÷ 71 = 1.4, so two buckets, with the balance absorbed by reveals and rough patches.
- Confirm the substrate has stabilised. New cement plasters made of Atlas mortars need one week per centimetre of thickness, and concrete walls at least 28 days.
- Clean back to a sound surface, removing dust, dirt, lime, oil, grease, wax and residues of oil and emulsion paints; substrates carrying biological growth are washed with a biocidal agent first.
- Fill gaps and irregularities, priming repair areas with a penetrating emulsion beforehand — the consolidating primers in the same range handle that stage.
- Stir to a uniform consistency immediately before use, straight from the bucket, with nothing added.
- Apply uniformly across the whole surface by roller, brush or machine, taking the elevation in one pass so suction equalises across it.
- Render after 4 to 6 hours, once the mass has dried completely, and wash tools in clean water directly after use.
Renders World supplies this bucket to trade applicators working to that sequence, and the quartz primer application guide for EWI systems covers tool choice and weather planning in more depth. Earlier stages — cleaning, making good and consolidating — sit in the wall preparation method for thin coat render.
Installation Notes — Site Conditions Worth Planning Around
The temperature window applies to three things at once, and the substrate is the one that catches people out on a bright cold morning. Working from the shaded side keeps all three inside the range for longer.
- Keep it off aluminium and copper. The sheet lists aluminium, copper and their alloys as incompatible materials, so mask base tracks, aluminium beads and rainwater goods before rolling out — a five-minute job that protects the profile.
- +5 °C to +30 °C covers mass, substrate and ambient, so a wall still cold from overnight is worth checking before the first bucket is opened.
- Store above freezing. Below 0 °C the product freezes and irreversibly loses its performance, which makes a frost-free store the whole of winter storage planning.
- Shade the drying film. Protect the primed surface from direct sunlight, wind and precipitation during application and while it dries, and the quartz beds down evenly.
- A pause is covered. If the finish is delayed, the dried film protects the unrendered facade for up to half a year, so a weather-hit programme can wait for a better window.
The 25 kg Bucket Against the 15 kg — Sizing the Order
Atlas Cerplast quartz top coat primer white 25kg and its smaller twin are one formulation in two pack sizes, so the choice is purely a quantity decision. Both sizes also carry the three DEKO M-matched colours, which the 5 kg and 10 kg buckets do not.
| Pack | Coverage at 0.35–0.30 kg/m² | When to order it |
|---|---|---|
| Cerplast 25 kg | 71–83 m² per bucket | Full elevations, whole-house runs |
| Cerplast 15 kg bucket | 43–50 m² per bucket | Single elevation, reveals, top-ups |
Buying one 25 kg bucket plus one 15 kg for a mid-size semi is usually tidier than three small packs, because every opened bucket is a tinting batch and fewer batches means fewer chances of a visible edge.
Is Cerplast the Right Key Coat for Your Finish?
Compatibility here is decided by the finish, not by the substrate, and this is the point where the documents are more specific than the marketing usually is.
- Yes — for Atlas mineral, acrylic and acrylic-silicone renders and mosaic DEKO M. Those are the finishes the data sheet names, and the EPS product sheet of BBA 13/5018 pairs Cerplast with Atlas Cermit Mineral, Atlas Acrylic Render and Atlas Acrylic-Silicone Render.
- Yes — on the Roker MW system with a mineral finish. The mineral wool product sheet is stricter still, naming Cerplast as the key coat used with Atlas Cermit Mineral.
- Not for Atlas silicone or silicone-silicate finishes. Both product sheets give Atlas Silkon ANX as the key coat for those renders — worth confirming at order stage, and the primer comparison for thin coat systems sets out how the key coats divide by finish type.
- Smaller quantity? The 15 kg pack is the identical mass in a pack that suits one elevation.
Renders World lists the whole white quartz top coat primer format in a 25 kg trade bucket alongside the consolidating primers, so a mixed-substrate job can be specified from one range.
Cerplast Coverage, Compatibility and Certification Questions
How many buckets does a 100 m² elevation take?
Two, on the certified planning rate. The working is worth keeping:
- 25 kg ÷ 0.35 kg/m² = 71 m² per bucket at the upper certified consumption.
- 100 m² ÷ 71 m² = 1.4 buckets, rounded up to two, with the surplus covering reveals and absorbent patches.
Can Cerplast go under a silicone render?
The Atlas documents route silicone and silicone-silicate finishes to Atlas Silkon ANX instead, in both the EPS and the mineral wool product sheets of BBA 13/5018. Staying with the key coat the certificate names for your chosen finish keeps the build-up inside the assembly that was tested, which is the position a warranty provider will look for.
What conditions does application need?
Mass, substrate and ambient temperature all between +5 °C and +30 °C, with the surface protected from direct sun, wind and rain while it dries over four to six hours. Cool, still, overcast days are ideal, and an overnight dry before rendering is a sound habit on damp autumn jobs.
Which pack size is better value on a full house?
The 25 kg bucket carries 71 to 83 m² against 43 to 50 m² from the 15 kg, so a whole-house run is usually one large pack plus one small rather than a shelf of small ones. Fewer tinting batches is the second reason, and on a coloured base it is the more important one.
How long does an unopened bucket keep?
Twelve months from the production date printed on the packaging, stored sealed, dry and cool, below +30 °C. Frost is the limit that matters over a UK winter — below 0 °C the mass separates irreversibly — so a frost-free store keeps stock usable through to spring.
Does using Cerplast make a wall BBA certified?
Certificate 13/5018 covers the complete Atlas/Aval external wall insulation system — adhesive, boards, fixings, basecoat, mesh, key coat and finish — installed by contractors registered with the certificate holder. Specifying Cerplast puts one certified component in place, and the certification value comes from keeping the remaining layers within the same documented system.
Technical Documentation for Atlas Cerplast
- Atlas Cerplast technical data sheet (PDF) — technical data, consumption, substrate preparation and storage.
- 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)