Description
Renders World stocks this bag inside the concrete effect render range, where it is the mineral, hand-textured route rather than a ready-mixed paste. Every figure below is read from the Atlas technical sheet fetched during this audit, and the specification has changed as a result.
Where Atlas Cermit WN Sits in an ETICS Build-Up
Atlas Cermit WN smooth render 25kg is a white cement-lime render with aggregate up to 1.0 mm, declared class A1 to EN 998-1, laid at about 4 mm so a silicone mould can impress a wood grain. The texture is pressed into the wet layer rather than floated into it, which is why the timing between trowel and mould governs the finish more than the mix does.
Atlas positions it as a decorative and protective thin-coat finish for the outside of new and existing buildings, in two places: as the finishing coat of an insulation system, and directly on flat, prepared mineral backgrounds. The sheet is specific about where it belongs and where it hands over to another Atlas product.
- Facade of an EPS insulation system and facade of a mineral wool insulation system — both listed as suitable, which is what makes this a finishing coat rather than a stand-alone render.
- Facade of a single-leaf wall, and concrete or traditional cement and cement-lime plasters once seasoned and primed.
- Every location category on the sheet is marked suitable — urban, industrial, rural, damp ground near water, close to trees and greenery, and shaded elevations.
- Ceiling soffits take Atlas Cermit MN instead, and walls inside a building take Atlas Cermit N-100, as do interior gypsum plasters and plasterboard. Those are the sheet's own substitutions, not ours.
Why Applicators Specify This Wood-Texture Mineral Render
Four documented properties do the work here, and one of them is the reason the material reaches shaded and planted sites so often. Renders World carries it as a 25 kg bag, the only pack Atlas publishes.
- Class A1 reaction to fire, EN 998-1, declaration of performance 108/1/CPR — declared for the render itself, which is a strong starting point on any project where the facade specification is fire-led.
- pH 12 plus a water repellent in the mix — the sheet ties that high alkalinity and the hydrophobic additive directly to natural resistance against mould fungi and algae, which is why shaded, tree-lined and urban sites all sit in the suitable column.
- Microfibre structural reinforcement in a polymerised cement-lime mortar based on white cement, credited by Atlas with high resistance to micro-cracking, so an impressed grain keeps its edges as the facade moves.
- Carbonation over time — a mineral render continues to reduce its own absorption and harden its structure in service, and Atlas presents that as increasing chemical resistance rather than as a fixed figure.
- Water absorption Wc1 and water permeability ≤ 1 ml/cm² after 48 hours, both measured after the required seasoning cycles, so driven rain is handled by the render itself before the stain goes on.
Declared Specification for Atlas Cermit WN, and What Is Not on the Sheet
Everything in this table comes from the Atlas sheet for this product. Three values that were published here previously have gone, and the reasons are set out beneath it.
| Parameter | Value on the Atlas sheet |
|---|---|
| Composition | White cement and lime, selected dolomite aggregates and quartz powders, modifiers, water repellent |
| Colour and texture | White, imitating wood once the silicone mould is impressed |
| Maximum aggregate | up to 1.0 mm |
| Application thickness | approx. 4 mm, combed with a 10 mm notched trowel, then re-smoothed |
| Consumption | approx. 2.5–3.0 kg/m², exact value established by a trial on the substrate |
| Mixing ratio | 0.21–0.24 l water per kg — 5.25–6.0 l per 25 kg bag |
| Rest then remix | 5 minutes |
| Pot life | approx. 1.0 hour |
| Wait before texturing | approx. 20–60 minutes, weather dependent, to be closely controlled |
| Hard | after 24 hours |
| Atlas Bejca stain | after 3 days, at +20 °C and 50% air humidity |
| Working temperature, substrate and ambient | +5 °C to +30 °C |
| Reaction to fire | class A1, EN 998-1, DoP 108/1/CPR |
| Water absorption | Wc1 |
| Water permeability after seasoning cycles | ≤ 1 ml/cm² after 48 h |
| Water vapour permeability | μ ≤ 30 declared; Sd between 0.14 m and 1.4 m, category V2, medium, with the Bejca stain |
| Adhesion after required seasoning cycles | 0.3 N/mm², FP:B |
| pH | 12 |
| Silicone mould size | 2 m × 0.2 m |
| Packaging | 25 kg paper bags |
| Shelf life | 12 months from the production date on the bag |
| Thermal conductivity | not declared on this sheet — omitted |
Vapour permeability reads twice, and the two readings answer different questions. The declared EN 998-1 figure is μ ≤ 30 for the render, while the diffusion-equivalent air layer of Sd 0.14–1.4 m puts the finished, stained surface in category V2, medium — so moisture keeps a route outward, but the stain is part of that classification and belongs in any breathability calculation for the wall.
Reaction to fire belongs to the render at product level here, not to a wall. Class A1 is declared under EN 998-1 for the mortar in the bag; the performance of a finished external wall is a build-up question, confirmed with the system holder and against current Approved Document B guidance for the building in question.
This render is not covered by BBA Agrément Certificate 13/5018. That certificate was fetched and its component list read in full: its mineral finishing coats are named as Atlas Cermit Mineral in the SN, DR and SN-MAL grades, and Cermit WN is absent. What the Atlas sheet does give is European Technical Assessment ETA 06/0173 for the Atlas Roker system, plus Polish national assessments ITB-KOT-2020/1616 edition 3 for Atlas ETICS, ITB-KOT-2021/1919 edition 2 for Atlas Roker and ITB-KOT-2020/1188 edition 1 for Atlas Roker EPS — assessments of those systems, which a UK specifier reads as evidence about the system, not as UK certification of this bag.
How to Apply Atlas Cermit WN — Mixing, the 4 mm Layer and the Mould
The whole job turns on one interval: the render is smoothed flat, then left to stiffen and surface-dry for 20–60 minutes before the mould goes in. Atlas asks for that time to be closely controlled, because weather moves it within the same day.
- Dry-mix the bag contents first in a bucket, then pour into water at 5.25–6.0 l per 25 kg and mix mechanically to a homogeneous mass.
- Rest for 5 minutes and remix. Use the batch within about one hour, restirring occasionally to hold consistency and adding no further water.
- Lay it on evenly at approximately 4 mm with a smooth float, comb it through with a 10 mm notched trowel held at an angle to equalise the layer, then smooth it again.
- Coat the 2 m × 0.2 m silicone mould thoroughly with Atlas anti-adhesive release agent before every impression, and clear render out of the mould's recesses as you go.
- Impress the grain once the surface has stiffened and lightly dried, working wet on wet so no smoothed section skins before the next one joins it. Plan breaks at corners, setbacks and downpipes.
- Wash the mould out with water and detergent at the end of every session. Atlas warns that release-agent residue left on it leads to permanent distortion of the mould, which is the one consumable on this job worth protecting.
The render is hard after 24 hours and ready for the Atlas Bejca tinted impregnant after 3 days at +20 °C and 50% humidity — longer in cooler UK conditions, since that figure is tied to those setting conditions. Sequence and tooling for the whole finish are covered in the concrete-effect render application guide, mould technique in the guide to wood and brick stencils for render, and the colour step in the guide to sealers for concrete-effect renders. The teak, walnut and birch Bejca tins and the release agent all sit in the same collection as this bag.
Substrate Seasoning and the Named Key Coat
Atlas gives a waiting period and a priming instruction for each background, and one of them needs no primer at all — worth knowing before ordering a bucket you do not need.
| Substrate | Seasoning | Priming |
|---|---|---|
| Reinforced ETICS layer in Atlas Stopter K-50 | min. 3 days | No key coat required |
| Reinforced ETICS layer in other Atlas adhesive mortars | min. 3 days | Atlas Cerplast |
| New cement and cement-lime plasters | min. 7 days, moisture 4% | Atlas Cerplast |
| Concrete backgrounds | min. 28 days, structural moisture below 4% | Atlas Cerplast |
Those periods assume +20 °C and 50% air humidity, so a cool British spring extends them. Atlas Cerplast is the named key coat, and a Cerplast bucket is stocked among the trade-size exterior render primers; make good with a levelling mortar and prime repairs with an Atlas Uni-Grunt emulsion first, as the sheet directs. Atlas Base Coat Paint is a different job — an interior base coat under acrylic or latex paint — and no fetched document places it beneath this render, so it is named here only to keep the two apart. The equivalent groundwork sequence is set out in the wall preparation method for UK render projects.
Quantities and Cost per Square Metre from a 25 kg Bag
Consumption is published as approximately 2.5–3.0 kg/m², and Atlas adds that the exact value is established by a trial on the substrate being rendered — which is the honest basis for an order on this product.
- Coverage per bag: 25 kg ÷ 3.0 kg/m² = 8.3 m²; 25 kg ÷ 2.5 kg/m² = 10 m², so 8.3–10 m² per 25 kg bag.
- A 40 m² elevation: 40 m² ÷ 8.3–10 m² per bag = 4.0–4.8 bags, so five bags as a starting quantity.
- Price: Atlas Cermit WN smooth render 25kg was listed at £24.80 per 25 kg bag and in stock when the product endpoint was read in August 2026. No VAT treatment was displayed, so none is stated here.
- Material cost per square metre: £24.80 ÷ 10 m² = £2.48/m² at the lean end, £24.80 ÷ 8.3 m² = £2.99/m² at the heavy end, render only, before key coat, release agent and stain.
One thing to carry into the order: a 4 mm layer of a cement-lime mortar would ordinarily consume more than 3.0 kg/m², so the sheet's two figures do not reconcile arithmetically. Treat the published consumption as the planning figure, run the trial panel Atlas asks for before committing to a quantity, and confirm the number with Renders World for anything above a single elevation.
Where the Sheet Sends You to a Different Atlas Product
Cermit WN is not the answer to every building on the list, and the sheet says so directly. Reading it that way saves specifying a mineral wood texture into a setting Atlas steers away from.
| Project type | Atlas position on the sheet |
|---|---|
| Housing, public, education, office, health, retail and service buildings | Suitable |
| Passive and energy-efficient construction | Suitable |
| Industrial buildings, industrial warehouses, transport structures, farm and livestock buildings | Atlas silicone render recommended instead |
| Ceiling soffits | Use Atlas Cermit MN |
| Walls inside a building, interior gypsum plaster and plasterboard | Atlas Cermit N-100 recommended |
Heritage buildings are the one row this audit will not publish. The 2020 edition of the sheet points them to Atlas Cermit PS, while the current edition's recommendation column cannot be resolved against that row unambiguously, so the value is omitted and worth confirming with Atlas before a conservation specification.
Is Atlas Cermit WN Right for Your Elevation?
- Yes, for an impressed wood-grain facade over an EPS or mineral wool insulation system, or on seasoned concrete and cement plasters, where a class A1 mineral finish suits the specification.
- Yes, for shaded, planted or urban sites, where pH 12 and the water repellent are the documented reasons this material is marked suitable across every location category.
- Plan the labour, not just the material — one hour of pot life, a 20 to 60 minute window before texturing, and one 2 m × 0.2 m mould set the size of a day's panel.
- Budget the whole finish in one order: Cerplast key coat, the release agent, and Bejca in teak, walnut or birch, all listed in the wood and concrete-effect finishes range at Renders World.
Atlas Cermit WN: Quantities, Compatibility, Conditions and Classification
How many bags for a wall, and how firm is that number?
Work on 8.3 to 10 m² from a 25 kg bag, from the published 2.5–3.0 kg/m², which puts a 40 m² elevation at five bags. Atlas asks for a trial on the actual substrate to fix the rate, and a 4 mm layer suggests the real figure sits at the heavy end, so order with a margin.
What goes under it, and what goes over it?
Underneath: Atlas Cerplast on concrete, cement plasters and reinforced ETICS layers made with Atlas adhesives other than Stopter K-50, which needs no key coat. Over the top: Atlas Bejca tinted impregnant after three days, which is what gives the grain its colour, applied with the release agent kept off the wall itself.
What conditions does the sheet allow?
Substrate and surroundings between +5 °C and +30 °C, with the fresh work protected from direct sun, wind and rainfall both during application and while it dries. Setting times quoted for hardness and staining assume +20 °C and 50% humidity, so allow longer in a cool spell.
Is this render BBA certified, and what is its fire class?
Class A1 for reaction to fire is declared for the render under EN 998-1 in declaration of performance 108/1/CPR. It is not a component of BBA Certificate 13/5018, whose mineral finishing coats are the Cermit SN, DR and SN-MAL grades; the Atlas evidence for this product is ETA 06/0173 and three Polish ITB national assessments, all held at system level.
Technical Documentation Retrieved for This Page