SILICONE RENDER

Silicone, silicone-acrylic, silicate-silicone and acrylic binders all sit in this range, and their figures are not interchangeable: consumption runs from 1.5 kg/m² on the 1.0 mm machine grade to 3.5 kg/m² for an Atlas finishing coat inside its certified build-up. Colour is mixed to order here, on separate Atlas and Ceresit benches.

Where a Thin-Coat Silicone Finish Belongs on a UK Wall

A silicone render declared to EN 15824:2017 gives a specifier three comparable numbers — vapour permeability, water absorption and adhesion — and those three decide whether a finish suits an exposed UK elevation. The range sits inside the wider Renders World rendering materials catalogue, so the key coat, basecoat and mesh beneath the finish come off the same order.

What the data sheets actually govern is substrate age and moisture, and the two most fully documented products in the range do not agree on it. Plan the programme around the stricter figure and the finish goes on when it is meant to.

The concrete line is the one that catches programmes out: Ceresit wants three months, Atlas accepts twenty-eight days. On a new-build slab-and-block elevation that difference alone can decide which brand goes on the wall.

Binder, Class and Scope: What Specifiers Are Actually Comparing

Seven declared figures separate one silicone render from another once the colour is settled, and each one is declared per product rather than per range. All of them are read straight from the current sheets and the Agrément certificate.

• Two vapour classes, not one. CT 74 and CT 76 declare V1 to EN 15824; the Atlas base, Gemini RS and CT 174 Machine declare V2 at Sd 0.14–1.4 m. On a solid wall drying outward, that class is the first thing to check.
• Adhesion splits the same way. The three Ceresit finishes declare 0.6 MPa to EN 15824; the two Atlas ranges declare 0.35 MPa. Both are declared values against the same test, so they compare directly.
• Consumption is the real cost line. From 1.5 kg/m² on CT 174 Machine at 1.0 mm, through 2.1–2.5 kg/m² on CT 74 and CT 76 at 1.5 mm, to 3.1–3.4 kg/m² on those same two at 2.0 mm.
• Working windows differ by brand and are never averaged. Atlas runs +5 °C to +30 °C, CT 74 and CT 76 run +5 °C to +25 °C, and CT 174 Machine runs +5 °C to +30 °C, all below 80 % relative humidity.
• Deep shades are a build-up decision. The Atlas sheet allows HBW above 15 % over a Hoter U2 or U2-B reinforced layer and HBW above 6 % over Stopter K-100; Gemini RS allows HBW above 15 over Stopter K-50, K-20 or Grawis U with a 5 mm layer and double Atlas 150 mesh.
• Certificate scope belongs to an assembly. BBA Agrément 13/5018 certifies the Atlas/Aval EPS system and names Atlas Silicone Render, Atlas Silicone-Silicate Render and Atlas Acrylic Render among its finishing coats. Gemini RS is not in that component list, so it is specified on its own DoP 280/CPR instead.
• Colour is a service here, not a stock list. The printed palettes are documented — 480 SAH shades on the Atlas base and 406 on Gemini RS — and beyond them Renders World tints to order across more than 1,000 available colours, on separate Atlas and Ceresit machines so neither tinting system touches the other. A shade from a different manufacturer can be matched from a reference where an elevation has run short.

Selection Guide — Match the Render to the Elevation

The Renders World selection below is sorted on binder chemistry and grain, which is what a buyer actually chooses on, rather than pack size — every product here is a 25 kg container. Read across to the specification, then follow the product name.

How to Apply a Thin-Coat Finish: Key Coat, Coverage, Wet Edge

Applying well is mostly a matter of preparing the layer underneath and then never stopping mid-panel. The certificate is specific about which key coat goes under which finish, and matched exterior render primers carry those products.

1. Key-coat the cured basecoat. BBA 13/5018 pairs Atlas Silkon ANX with the Atlas silicone and silicone-silicate finishes, and Cerplast with the mineral, acrylic and acrylic-silicone coats, all at 0.25–0.35 kg/m². Under the Ceresit renders the sheets call for CT 16, tinted close to the topcoat shade.
2. Embed the reinforcement first. The certified basecoat carries Atlas 150 or 165 alkali-resistant reinforcing mesh, and the finish only performs as declared once that layer is cured.
3. Stir, never thin. Every product here ships ready to use; the Atlas and Ceresit sheets both forbid blending with other materials, and CT 74 permits at most 1 % clean water.
4. Lay to aggregate thickness. Trowel with stainless steel at the depth of the largest grain, drawing surplus back into the container and re-stirring it.
5. Texture inside the open time. Both the Atlas and Ceresit sheets give roughly 15 minutes before skin formation at 20 °C; float in circular motions to raise the lambskin pattern.
6. Protect the cure. Atlas quotes about 24 hours drying at 20 °C and 60 % RH; the Ceresit sheets give 24 to 48 hours to rain resistance depending on temperature.

One rule sits above the rest: the Atlas sheet states that hand and machine textures differ and that combining the two application methods on one building is not permissible. Where the season is against you, Atlas Eskimo is the sheet's named route to working above 0 °C on the Atlas renders, and the step-by-step thin-coat method for UK walls covers the full sequence.

How Many Buckets — the Arithmetic Shown

Two coverage figures exist for the Atlas finish and they belong to different scopes, so both are worth ordering against. The certificate figure is the higher one, which makes it the safe basis for a take-off.

• Certified build-up, 100 m²: 100 m² × 2.5 kg/m² = 250 kg ÷ 25 kg per container = 10 containers; 100 m² × 3.5 kg/m² = 350 kg ÷ 25 kg = 14 containers. Add whatever cutting and detailing allowance your own take-off uses.
• Data-sheet figure for comparison: the Atlas sheet quotes from 2.2 kg/m² by hand at 1.5 mm and from 1.9 kg/m² by machine — lower than the certified range, and scoped to an even substrate rather than to the certified system.
• Cost of a grain step: 2.8 kg/m² ÷ 2.2 kg/m² = 1.27, so moving from 1.5 mm to 2.0 mm by hand takes 27 % more material for the same wall.
• Key coat for the same wall: 100 m² × 0.25–0.35 kg/m² = 25–35 kg.

Fire Class and Certificate Scope, Read Correctly

A reaction-to-fire class belongs to whatever was tested, and for these products two different things were tested. A class is published here only against the assembly the document names, which is why the same Atlas finish appears twice below with two different answers.

• Product scope, Atlas base: DoP 145/3/CPR under EN 15824:2017 declares A2-s1, d0 for the render itself.
• System scope, same render: in BBA Agrément 13/5018 the construction using a silicone finishing coat over Silkon ANX, a Stopter K-20 or Hoter U basecoat, Atlas 150 or 165 mesh and EPS to a maximum 250 mm is classified B-s2, d0. That is the stricter of the two and the one to quote when a wall build-up is being assessed.
• Height limits come with it. The certificate states the system should not be used on buildings with a storey more than 18 m above ground level in England, Wales and Northern Ireland, or a storey 11 m or more above ground level in Scotland, where it also should not sit 1 m or less from a boundary. B-s2, d0 constructions may be used at any proximity to a boundary in England, Wales and Northern Ireland.
• Ceresit classes are named per system. CT 74 and CT 76 both reach A2-s1, d0 in Ceresit Ceretherm Universal MW; CT 74 is B-s1, d0 in Universal EPS, Popular, Classic, Premium and the two Wool systems, and B-s2, d0 in Impactum and Universal XPS.
• Where a class is absent, the page says so. The Gemini RS sheet carries no reaction-to-fire line and Gemini RS is absent from the BBA component list, so no class and no BBA claim is made for it here.
• Certificates of reference are not product certificates. The CT 74 sheet lists BBA Certificate 14/5142 as a document of reference for the Ceretherm system, which is a different statement from a product being certified.

Durability is scoped the same way: the certificate states the system will remain effective for at least 30 years under normal service conditions when installed and maintained to its terms, which is a system figure and not a property of any container.

Installer Notes That Change the Order Quantity

Five details on these sheets change what goes on the order rather than what happens on the trowel, and they are the ones most often missed at quotation stage.

• Decide hand or machine before you price. Machine application is approved for the 1.5 mm Atlas grain only, and the sheets forbid mixing methods on one building — so a part-pumped elevation is a single-method job from the start.
• Gemini RS caps unrestricted intense colour at 10 % of the facade. Above that, the sheet requires the HBW above 15 route with its specified reinforced layer, which is a basecoat and mesh decision, not a tinting one.
• CT 74 limits intense dark shades to small areas such as architectural details. Where a whole elevation is going dark on a Ceresit system, that constraint belongs in the quote before the shade is signed off.
• Tinting to order changes what arrives, not what the label declares. Declared shelf life runs from the manufacturer's production date — 12 months on the Atlas renders and CT 74, 18 months on CT 76 — and mixing on site does not restart that clock. What it does change is how much of it is left: a container tinted against your order has not been standing as pre-coloured stock, so more of the declared life arrives with the material.
• The Atlas sheet names its own renovation route. An aged Atlas thin-coat facade is refreshed by overpainting with a silicone masonry paint — Salta N on the Atlas base, and Salta, Salta N or Salta N Plus on Gemini RS. No sheet in this range states a service life in years, so maintenance is planned on intervals rather than on an expiry date.

Is This Range Right for Your Elevation?

Five checks turn this range into a shortlist, and each one points at a specific next move.

• Specify from this range when the wall sits above the damp-proof course, the basecoat and mesh are already inside one manufacturer system, and you need declared EN 15824 figures for the submission.
• Choose mosaic plinth finishes instead below the damp-proof course and anywhere ground splash is persistent, since that is what plinth exposure rewards.
• Settle the shade against a physical reference from the printed shade catalogues and samples, because grain changes how a tint reads in daylight and the Atlas and Ceresit palettes are separate books.
• Work through the ranked buying guide for UK facade finishes where the decision is still open between brands, exposure and budget.
• Bring the build-up, not just the shade. The reinforced layer decides how deep a tint can go and which fire scope applies, so send the basecoat, mesh and insulation to Renders World with the colour reference and the specification comes back matched. Tinted orders go out on a next-day UK-wide delivery service, which is a site-wide arrangement rather than a per-product stock promise.

FAQ — Coverage, Compatibility, Conditions and Colour

How much material does 100 m² take?

On the Atlas finish inside its certified build-up, 100 m² at 2.5–3.5 kg/m² works out at 250–350 kg, which is 10 to 14 containers of 25 kg before your detailing allowance. On CT 74 or CT 76 at 1.5 mm the rate is 2.1–2.5 kg/m², and on CT 174 Machine at 1.0 mm it drops to about 1.5 kg/m².

Which key coat goes under which finish?

The pairing is set by the document, not by preference, and getting it right is what keeps the tested build-up intact.

• Atlas silicone and silicone-silicate finishes: Atlas Silkon ANX, at 0.25–0.35 kg/m² per BBA 13/5018.
• Atlas mineral, acrylic and acrylic-silicone finishes: Atlas Cerplast, at the same rate.
• Ceresit CT 74, CT 76 and CT 174 Machine: Ceresit CT 16, tinted close to the topcoat shade.

Can a colour outside both catalogues be mixed?

Yes. Beyond the documented 480-shade Atlas SAH palette and the 406 shades listed for Gemini RS, more than 1,000 colours are available to order, tinted on separate Atlas and Ceresit machines so the two systems never share a bench. A shade from another manufacturer can be matched from a code or a physical sample, which is the usual route when an elevation has run short part-way through and the original supply is no longer available.

What separates CT 74 from the Atlas base?

CT 74 declares V1 vapour permeability and 0.6 MPa adhesion, against V2 at Sd 0.14–1.4 m and 0.35 MPa for the Atlas base, and its sheet describes the binder as a water dispersion of silicone and acrylic resins rather than a silicone-siloxane blend. The Atlas base offsets that with a wider working window and the 480-shade SAH palette.

What conditions can these renders go on in?

Atlas products apply between +5 °C and +30 °C, Ceresit CT 74 and CT 76 between +5 °C and +25 °C, and CT 174 Machine between +5 °C and +30 °C, all at relative humidity below 80 %. Atlas Eskimo is the sheet-named additive for working above 0 °C on the Atlas renders, and it is not a Ceresit component.

How is an aged thin-coat facade brought back?

By overpainting with the silicone paint the sheet names: Salta N for the Atlas base, Salta, Salta N or Salta N Plus for Gemini RS, and CT 48 or CT 49 for the Ceresit renders, with CT 54 silicate paint also permitted over CT 174 Machine. None of these sheets states a service life in years, so a facade is reviewed on condition rather than on a countdown.

Does any single container carry a fire class for the wall?

No — a container carries a product declaration, and the wall carries a system classification. BBA Agrément 13/5018 records that the Atlas/Aval EPS system is restricted under Requirement B4(1) of the Building Regulations 2010 for England and Wales, and it sets the storey-height limits quoted above, so the assessment always runs on the assembly.