Both finishes in this comparison sit inside the Renders World premium silicone render range, and both are declared to EN 15824. That shared standard is precisely why the familiar shorthand — silicone breathes, acrylic does not — collapses the moment the two data sheets are laid side by side. This page rebuilds the comparison from the sheets themselves: Atlas Silicone Render, Atlas Acrylic Render and Ceresit CT 74, each read at its own declared scope, with the figures that no source covers left out rather than rounded into a story.
What Silicone and Acrylic Thin-Coat Renders Share Before They Differ
Silicone render vs acrylic render UK selection turns on declared values, and both Atlas sheets declare the same diffusion band of Sd 0.14 to 1.4 m under EN 15824, which means breathability alone rarely settles the specification. The category words differ while the numbers do not: Atlas describes its silicone finish as V2 – high and its acrylic finish as V2 – medium, yet both print the identical diffusion range. Treat the adjective as a brand descriptor and compare the Sd figures, because that is the line an assessor will read.
- Diffusion band: 0.14 ≤ Sd < 1.4 m on the Atlas Silicone Render sheet and 0.14 ≤ Sd ≤ 1.4 m on the Atlas Acrylic Render sheet — the same working range, so a wall build-up calculation treats them alike.
- Adhesion: 0.35 MPa declared for the silicone finish and ≥ 0.35 MPa for the acrylic, both to EN 15824, which is why the reinforced basecoat beneath them is unchanged by the binder decision.
- Product-level reaction to fire: A2-s1, d0 on both sheets — under DoP 145/3/CPR for the silicone and DoP 137/CPR for the acrylic. That is a class for the material in the bucket, never for a rendered wall.
- Governing standard: EN 15824, external renders on organic binders, published in the UK through BSI — so both products are assessed against the same test regime.
The consequence is worth stating plainly: anyone choosing on vapour permeability alone between these two Atlas finishes is choosing on a difference the documents do not record. The real separations sit elsewhere — in the substrates each sheet names, the reflectance conditions each attaches to deep shades, and the certificate scope behind each class.
Five Criteria That Decide Between Silicone and Acrylic Render
Run these five in order. Each is answerable from a fetched sheet, and each has a documented threshold rather than a rule of thumb, which is what makes the decision defensible on a specification.
- Which substrates does the sheet name? The Atlas Silicone Render sheet marks both EPS and mineral wool insulation systems as places of use. The Atlas Acrylic Render sheet names polystyrene and XPS boards and does not list mineral wool — a scope limit, and the single most decisive line for anyone specifying over the mineral wool insulation range.
- What reflectance does the shade carry? Atlas permits its silicone finish at HBW above 15% over a Hoter U2 or U2-B reinforced layer and above 6% over Stopter K-100. The acrylic sheet asks that colours with a diffuse reflection coefficient below 20% be avoided, and capped at 10% of the facade.
- What temperature window does the programme need? The silicone sheet runs +5 °C to +30 °C, extended to use above 0 °C once Atlas Eskimo is added; the acrylic sheet runs +5 °C to +25 °C with no such route.
- Whose certificate is being relied on? BBA 13/5018 certifies the Atlas/Aval EPS system, and its component list, not any bucket on its own.
- What is the consumption at the chosen grain? From 2.2 kg/m² for the silicone at 1.5 mm by hand against 2.5 kg/m² for the acrylic at N-15 — a real quantity difference on a large elevation.
Silicone Render: What the Declared Values Actually Say
Atlas Silicone Render is a mixture of silicone and siloxane resins with dolomite aggregates and quartz flours, reinforced with cellulose fibres, and its sheet claims an active photocatalytic self-cleaning effect alongside strong surface hydrophobisation. Water absorption is declared as In2 – average. Consumption starts at 2.2 kg/m² by hand at 1.5 mm grain and 1.9 kg/m² by machine, so 25 kg ÷ 2.2 kg/m² gives roughly 11.3 m² from a bucket before waste. Machine application is restricted to the 1.5 mm grain. For shoulder-season work, Atlas Eskimo is the sheet's own route to working above 0 °C, and the current white base carries the full 480-shade SAH palette.
Two scope points matter more than any of that. The 140 J impact strength and 30 m/s hail resistance the sheet advertises belong to the render combined with Atlas Stopter K-100 as a system, not to the bucket. And while the product declares A2-s1, d0, BBA 13/5018 classifies the certified build-up carrying this render — adhesives Stopter K-20, Hoter S or Hoter U, EPS to 250 mm, Stopter K-20 or Hoter U basecoat, Atlas 150 or 165 mesh, Cerplast or Silkon ANX key coat — as B-s2, d0. The stricter figure governs a wall: in England, Wales and Northern Ireland the certificate bars use where a storey sits more than 18 m above ground, and in Scotland at 11 m or more, or within 1 m of a boundary.
Then the category itself splits. Ceresit CT 74 is described on its own sheet as a water dispersion of silicone and acrylic resins, and it declares cat. V1 with Sd 0.14 m — a lower permeability category than the Atlas acrylic finish — alongside W3 water absorption and 0.6 MPa adhesion. Its fire classes are stated per Ceresit Ceretherm system: A2-s1, d0 in Universal MW, B-s1, d0 in Universal EPS and the Popular, Classic, Premium and Wool systems, B-s2, d0 in Impactum and Universal XPS. BBA 14/5142 appears there as a document of reference, which is system scope; the bucket is not a certified product.
Acrylic Render: Where the Declared Values Hold Up
Atlas Acrylic Render is built on a water dispersion of synthetic resins with dolomite aggregate and dispersed microfibres running through the render volume, and its sheet is explicit that the modern binder addresses the older acrylic limitations of low vapour permeability and soiling. Declared values are V2 – medium with the same 0.14 to 1.4 m band, W2 – medium water absorption, bonding ≥ 0.35 MPa and A2-s1, d0 at product level under DoP 137/CPR. Consumption is 2.5 kg/m² at N-15 and 3.0 kg/m² at N-20, so 25 kg ÷ 2.5 kg/m² is about 10 m² per bucket. Setting runs 12 to 48 hours depending on substrate, temperature and humidity — a longer and more weather-sensitive window than the silicone sheet's approximate 24 hours.
Two corrections belong here. The palette on the acrylic sheet is 400 SAH colours, not the 480 of the silicone range, which matters when a shade reference is quoted across both. And although BBA 13/5018 names Atlas Acrylic Render as a finishing coat of the certified EPS system at 2.5 to 5.0 kg/m², no reaction-to-fire row in that certificate names it — so no system fire class is published for it on this page. Where the sheet lists BBA 13/5018 and NSAI 10/0347 against the product while the certificate itself covers a system and its component list, read the system scope and specify accordingly.
Declared Performance Compared, Sheet by Sheet
Each column below is transcribed from that product's own fetched document at its own scope. Where a cell is empty of a figure, no document read this session covered it.
| Property | Atlas Silicone Render | Atlas Acrylic Render | Ceresit CT 74 |
|---|---|---|---|
| Binder base | Silicone and siloxane resins, cellulose fibres | Synthetic resin dispersion, microfibres | Silicone and acrylic resin dispersion |
| Vapour permeability (EN 15824) | V2 – high; Sd 0.14–1.4 m | V2 – medium; Sd 0.14–1.4 m | V1; Sd 0.14 m |
| Water absorption (EN 15824) | In2 – average | W2 – medium | W3 |
| Adhesion (EN 15824) | 0.35 MPa | ≥ 0.35 MPa | 0.6 MPa |
| Product-level fire class | A2-s1, d0 (DoP 145/3/CPR) | A2-s1, d0 (DoP 137/CPR) | Stated per system only |
| System fire class | B-s2, d0 in BBA 13/5018 build-up | Not named in BBA 13/5018 fire table | A2-s1, d0 in Ceretherm Universal MW |
| Consumption, 1.5 mm hand | From 2.2 kg/m² | 2.5 kg/m² (N-15) | 2.1–2.5 kg/m² |
| Application temperature | +5 to +30 °C; above 0 °C with Eskimo | +5 to +25 °C | +5 to +25 °C |
| Deep-shade condition | HBW >15% (Hoter U2); >6% (Stopter K-100) | Avoid below 20%; max 10% of facade | Dark shades limited to small areas |
| Insulation named on sheet | EPS and mineral wool | Polystyrene and XPS | EPS and mineral wool |
| Declared palette | 480 SAH colours | 400 SAH colours | Ceresit Colours of Nature |
Verdict: Which Render to Specify for Which UK Wall
The honest conclusion is narrower than the usual one, and more useful. Binder chemistry alone does not predict permeability across brands, so the difference between silicone and acrylic render is decided per product, from the sheet in front of you.
Mineral Wool and Stone Wool Build-Ups
Specify a finish whose own sheet names mineral wool. Atlas Silicone Render does, and Ceresit CT 74 declares A2-s1, d0 within Ceretherm Universal MW. The Atlas Acrylic Render sheet names polystyrene and XPS only, which is a documented scope limit rather than a predicted failure. Atlas Gemini RS makes the same point from the other side: its sheet directs mineral wool facades to the Atlas Roker system instead. Where a build-up is being compared at material level, the mineral wool and polystyrene comparison keeps each class at its own scope.
Dark and Saturated Shades
Deep shades are an adhesive decision as much as a colour one. Atlas ties HBW above 6% to a Stopter K-100 reinforced layer and HBW above 15% to Hoter U2, so the reinforced layer specified underneath sets how dark the facade can go. The acrylic sheet's own boundary is a diffuse reflection coefficient of 20%, with such colours held to a tenth of the elevation. Ceresit's Solar Protect sheet, often quoted here, recommends HBW at 15 or above and answers UV exposure and colour stability through added UV absorbers with a self-healing surface effect — it claims no heat or infrared reflection, so it is not the route to a deeper shade.
Cold and Shoulder-Season Programmes
The application envelope is a product property, not a binder property. Atlas Silicone Render reaches +30 °C and works above 0 °C with Atlas Eskimo added; both the Atlas acrylic and Ceresit CT 74 stop at +25 °C. Renovation of an aged Atlas silicone facade is covered on the same sheet by overpainting with Atlas Salta N, which is worth knowing before a wall is written off. For a ranked view across brands by exposure, the UK climate performance ranking works through the same sheets, and the Atlas and Ceresit brand comparison holds each certificate at its documented scope.
Key Takeaway: Read the sheet, not the binder name. Both Atlas finishes declare the same Sd 0.14–1.4 m band, while Ceresit CT 74 — a silicone render — declares the lower V1 category, so an acrylic render vs silicone render comparison built on breathability alone will mislead. Decide instead on the insulation each sheet names, the reflectance condition attached to the shade, and the certificate scope behind any fire class.
What to Confirm Before You Order
Three confirmations close out a clean order, and the arithmetic is short. For a 100 m² elevation at 1.5 mm: 100 m² ÷ 11.3 m² per bucket = 8.8, so nine to ten buckets of the Atlas silicone with waste allowance; 100 m² ÷ 10 m² = 10, so eleven of the acrylic. Confirm the reinforced layer, because it governs the shade limit; confirm which insulation sits behind, because it governs the binder; and confirm whether the project is relying on a system certificate, because that changes the permitted storey height. The Renders World thin-coat render range holds both finishes, and the wider rendering materials catalogue carries the primers, meshes and beads the same build-up needs. For the thicker single-pass alternative outside this comparison, the monocouche comparison sets out that family instead, and heritage and conservation work is handled in the silicate-silicone guidance.
Written by Mariusz Saja. Technically reviewed by Rafał Wyrzykowski. Last reviewed Aug 2026.
FAQ: Specifying Silicone and Acrylic Render in the UK
Can acrylic render be used over mineral wool insulation?
The Atlas Acrylic Render sheet names polystyrene and XPS boards as its insulation substrates and does not list mineral wool, so a stone wool build-up should be specified with a finish whose own document names it — Atlas Silicone Render, or Ceresit CT 74 within Ceretherm Universal MW. Ask the manufacturer's technical department to confirm anything outside a named system.
Which render is more vapour permeable?
Between the two Atlas finishes, neither: both declare 0.14 to 1.4 m diffusion under EN 15824, differing only in the category word Atlas prints beside it. Across brands the ranking can invert, since Ceresit CT 74 declares cat. V1 at Sd 0.14 m. Compare the Sd figures product by product rather than by binder name.
How many buckets does a 100 m² elevation take?
At 1.5 mm by hand, the Atlas silicone starts at 2.2 kg/m², giving 25 ÷ 2.2 = 11.3 m² per bucket and 100 ÷ 11.3 = 8.8, so nine before waste. The acrylic at 2.5 kg/m² gives 10 m² per bucket and ten buckets flat. Uneven basecoats raise both figures, so order the allowance.
Does an A2-s1, d0 render make the wall A2-s1, d0?
No. A2-s1, d0 on the Atlas sheets is a product-level class under EN 15824. BBA 13/5018 classifies the certified Atlas/Aval EPS build-up carrying the silicone render as B-s2, d0, with storey-height restrictions that differ between England, Wales and Northern Ireland and Scotland. Under current Approved Document B guidance, the assembly figure is the one that governs.
What maintenance should be planned for either finish?
No sheet read for this comparison states a service life or a washing interval, so none is published here. What is documented is the renovation route: an aged Atlas silicone facade is overpainted with Atlas Salta N per the render sheet, and the Ceresit sheets name CT 48 and CT 49 silicone paints for the same job.