Description
Architectural concrete on a rendered wall comes from technique, not stamps — and from a finish laid in two coats with a two-hour interval between them. Atlas Silkon BA is a ready-to-use silicone render with aggregate up to 1.2 mm, averaging 2.5 kg of material per square metre of finished wall.
Where Atlas Silkon BA Fits on UK Facades and Wet Rooms
Atlas Silkon BA concrete effect silicone render 20kg is a ready-mixed silicone-acrylic thin-coat finish with aggregate up to 1.2 mm, applied in two coats to EN 15824:2017 for architectural concrete elevations and interior wet areas. Renders World holds it inside the concrete and wood-effect render collection, where it is the silicone route to a fair-faced finish.
- External walls in EPS insulation systems: the sheet lists it as a component of the Atlas ETICS and ROKER kits, applied onto the reinforced layer once that layer has set.
- Prepared mineral substrates: concrete, traditional cement and cement-lime renders, and — internally — gypsum plaster and plasterboard.
- Bathrooms and under-shower zones: named for wet rooms and for application over existing ceramic tiles, once the tiles are primed and their adhesion verified.
Vertical work is its territory. The sheet excludes horizontal surfaces, surfaces under permanent contact with water or snow, and walls suffering rising damp, so those details are best answered by a dedicated plinth or waterproofing product and the wall above stays with Silkon BA.
Why Specifiers Choose Silkon BA for Architectural Concrete
- Texture is chosen on site: the sheet names four achievable reads — pitted architectural concrete, monolithic concrete, ribbed panels and smooth panels — so one bucket covers the whole vocabulary without a second product.
- Class W2 water absorption: declared under EN 15824 and backed by the surface hydrophobisers Atlas describes as Water Protect, which the sheet ties to low absorption and quick surface drying once rain stops.
- Clean Technology surface: high silicone resin content, siloxanes and biocides give a tight film that Atlas states resists mould, algae and lichen, with dust and dirt washed off by rainfall rather than anchoring in the texture.
- Dark shades with a stated condition: the Flex Tech polymer blend permits dark facade colours where the colour's light reflectance value (HBW) is above 15%, which keeps charcoal and graphite schemes inside the manufacturer's own thermal-stress envelope.
- Nine recommended colours, bespoke on order: the sheet confirms nine standard shades held stable by selected inorganic and organic pigments, with any other shade available to order.
Silkon BA Declared Performance and Technical Data
| Parameter | Declared value |
|---|---|
| Pack | 20 kg bucket |
| Average consumption | 2.5 kg/m² |
| Coverage per bucket | ~8 m² (derived) |
| Aggregate | up to 1.2 mm |
| Substrate and ambient temperature | +5 °C to +30 °C |
| Relative humidity, laying and setting | below 80% |
| Diffusion resistance | 0.14 m < Sd < 1.4 m |
| Second coat | after ~2 h at +20 °C, 50% RH |
| Drying | ~24 h, conditions-dependent |
| Standard | EN 15824:2017 |
| Declaration of performance | No. 272/CPR |
| Water vapour permeability | class V2 |
| Water absorption | class W2 |
| Adhesion | 0.35 MPa |
| Shelf life | 12 months from production date |
Class V2 is the band the same sheet expresses as 0.14 m < Sd < 1.4 m, so water vapour still moves out through the finish rather than being held behind it. The render is also fibre-reinforced in the bucket, which is why it takes a two-coat build at aggregate thickness without a separate mesh at finish level.
Three Polish national technical assessments cover the systems this render belongs to — ATLAS ETICS under ITB-KOT-2020/1616 edition 3, ATLAS ROKER under ITB-KOT-2021/1919 edition 2 and ATLAS ROKER G under ITB-KOT-2018/0583 edition 2. Each is held for the assembled kit, not for the bucket on its own, and none is a UK certificate; where a UK specification needs system-level evidence, ask Renders World for the current assessment documents before the build-up is fixed.
How to Apply Silkon BA in Two Coats
The product arrives ready to use, must not be diluted, thickened or mixed with anything else, and needs only stirring before work to even out consistency and colour across the bucket. There is no mixed pot life to watch; the timing that governs the day is the two-hour interval between coat one and coat two at +20 °C and 50% relative humidity.
- Lay coat one at aggregate thickness with a smooth stainless-steel or Venetian trowel, covering only the area the crew can return to on time.
- Apply coat two after about two hours, scraping back the surplus as you go and smoothing the surface towards the chosen texture.
- Texture immediately after coat two — a large-cell sponge roller or brush float for a pronounced read, or a Venetian trowel during initial set for monolithic smoothing and the scorched, burnished effect.
- Form grooves and panel joints either by scratching the fresh material along a spirit level with a flat screwdriver, or by taping coat one and pulling the tape straight after coat two.
- Keep every joint wet-on-wet and place planned breaks at corners, changes of plane, beneath downpipes and at colour changes, since a dried lap line stays visible.
Quantities follow the consumption line directly: 40 m² ÷ 8 m² per bucket = 5 buckets, and at 2.5 kg/m² a 120 m² elevation needs 120 × 2.5 = 300 kg, which is 15 buckets before any allowance for texture depth. The concrete-effect render application guide carries the full method across both binder routes.
How to Prime and Season the Substrate
| Substrate | Seasoning and moisture | Priming mass |
|---|---|---|
| Concrete | min 28 days, structural moisture below 4% | Silkon ANX or Cerplast |
| New cement or cement-lime render | min 7 days per 1 cm of thickness, moisture 4% | Silkon ANX or Cerplast |
| Reinforced layer in an ETICS build-up | min 1 day | Silkon ANX or Cerplast |
| Gypsum plaster, plasterboard (internal) | moisture below 2% | Uni-Grunt first, then Silkon ANX |
| Existing ceramic tiles | adhesion verified across the wall | Ultragrunt |
Hollows and unevenness are filled first with ZW 330 or Atlas rendering mortar over a substrate primed with Uni-Grunt, Uni-Grunt Ultra or Grunt NKP, and any biological growth is removed with Mykos Plus before priming begins. Cerplast, Uni-Grunt and Ultragrunt all sit in the Atlas and Ceresit exterior render primers range at Renders World, so the whole preparation stage can be ordered with the render.
Colour matters underneath a textured concrete finish, because the trowel exposes the primer at high points. Atlas Base Coat Paint is the tone-matched base the concrete- and wood-effect range uses for that job; the Silkon BA sheet itself names Silkon ANX, Cerplast and Ultragrunt as its priming masses, so treat the base coat as a colour step rather than a substitute for them.
Installation Notes: Texturing, Grooving and Site Protection
- Prove consumption on the wall: the sheet states that exact usage is established by a trial patch on the actual substrate, and a 2 m² panel settles both the figure and the trowel technique before the order is finalised.
- One production date per surface: mixing batches across a single elevation is the documented cause of shade variation, so buy the whole elevation together and check the date stamp on delivery.
- Shelter the work: protect the wall from direct sun, wind and precipitation during application and while it dries, roughly 24 hours, extending in high humidity and near +5 °C.
- Size panels to the weather, not the wall: the maximum area for one laying-and-texturing cycle is found experimentally for the substrate and the day, which on a two-coat product means planning by panel rather than by elevation.
- Clean tools with water at once: hardened residue comes off with Atlas Szop 2000, which is worth having on site before the first bucket is opened.
Silkon BA or the Mineral Concrete-Effect Route?
| Route | What the documents support | Choose it when |
|---|---|---|
| Silkon BA — silicone-acrylic, ready-mixed | V2 vapour class, W2 absorption, 0.35 MPa adhesion, dark shades at HBW above 15% | Exposed elevations, wet rooms, tiled substrates, deep shades |
| Mineral concrete and wood-effect renders in the same collection | Own sheets, plus a separate stain-and-sealer step for timber grain | Sheltered walls, wood-board effects, mineral binder preferred |
The split is binder and exposure, not appearance: both routes reach a convincing concrete read, and the silicone-acrylic option is the one carrying declared hydrophobic performance and an interior wet-area scope. Where the design wants timber grain instead, the guide to sealers for concrete-effect renders explains the staining sequence, and the decorative render collection shows the two routes priced side by side.
Is Silkon BA the Right Specification for Your Project?
- Specify it for exposed architectural concrete: full elevations, feature bays and contrast panels within EPS insulation build-ups, where a low-absorption, rain-washed surface keeps maintenance intervals long.
- Specify it for wet rooms and tiled walls: shower zones and bathroom feature walls, with Ultragrunt priming and a verified tile bond underneath.
- Keep it on vertical surfaces: horizontal details, areas in permanent contact with water or snow and walls with rising damp are outside the sheet's scope, so those are resolved separately and the render performs best above them.
- Order the preparation with it: Renders World lists the Atlas Silkon BA concrete effect silicone render 20kg bucket at £79.50 per 20 kg bucket, August 2026, currently shown as available. At 2.5 kg/m² one bucket covers about 8 m², so £79.50 ÷ 8 = £9.94/m² in material, with primer and any repair mortar priced on their own collection pages.
FAQ — Silkon BA Coverage, Priming and Dark Colours
How many buckets does a 40 m² elevation take?
Five, before any allowance for texture depth: 40 m² ÷ 8 m² per bucket = 5, working from the sheet's average 2.5 kg/m². Deeply pitted finishes carry more material than flat monolithic ones, so a trial patch on the actual substrate gives the figure to order against, and buying the elevation in one production batch keeps the shade consistent.
Can it go over existing ceramic tiles in a bathroom?
Yes, and the data sheet names the route: prime the tiles with Atlas Ultragrunt after confirming the tiles themselves are firmly bonded across the whole wall. Anything drummy comes off first, grout lines are levelled so coat one starts flat, and the finish is then built in the same two coats used externally.
What conditions does application need?
Substrate and air between +5 °C and +30 °C with relative humidity below 80%, held through laying and setting. Drying takes roughly 24 hours and stretches in damp cool weather, so shelter the wall from sun, wind and rain across that window and plan the two-coat cycle inside the settled part of the day.
Can it be used in dark facade colours?
Dark shades are permitted where the colour's light reflectance value (HBW) is above 15%, a condition the manufacturer ties to the Flex Tech polymer blend and its resistance to thermal stress. Nine recommended shades are held as standard and other colours are made to order, so confirm the HBW of a bespoke tint at the quotation stage.
How is the finished surface maintained?
Rainfall does most of the work, since Atlas describes the tight, biocide-protected film as one that dirt cannot anchor to and that dries quickly once a shower passes. Periodic washing down with clean water handles sheltered areas that rain does not reach, and Atlas Szop 2000 lifts hardened material splashes from adjacent surfaces.
Technical Documentation