Description
Renders World supplies this Atlas hybrid finish for solid-wall and insulated facades, where the buildup has to be documented as well as installed. Everything specified below comes from BBA Agrément Certificate 13/5018, read in full this session, and nothing has been substituted where that certificate is silent.
Where Atlas Silicone-Silicate Render Fits on Solid-Wall and Heritage Projects
Atlas Silicone-Silicate Render 25kg buckets are named in BBA Agrément Certificate 13/5018 as a finishing coat of the Atlas/Aval EPS external wall insulation system, applied at 2.5 to 3.0 kg/m² over a reinforced basecoat. The certificate scopes this render as one component of a certified build-up, which is exactly how it should be specified and quoted. Within the premium silicone render range at Renders World, it is the finish chosen where insulation boards are going on the wall and the client wants a silicone-silicate paste rather than a straight silicone one.
- Certified substrates, at system scope: masonry, normal-weight concrete, lightweight concrete, autoclaved concrete and no-fines concrete, on new or existing domestic and non-domestic buildings, with or without existing render.
- Existing walls: the certificate expects the system to go on where the inner surface shows no dampness other than condensation, so a five-minute internal check before ordering keeps the specification sound.
- Position in the build-up: a ready-to-use paste over the Atlas Silkon ANX key coat, which is the key coat the certificate ties to this render.
For the conservation route — consent, substrate compatibility and what a conservation officer will want to see — the heritage and conservation render guide works through the specification path.
Why Specifiers Choose a Silicate Hybrid on a Certified Build-Up
The commercial case here is predictability rather than headline performance. Three of the five points below come straight off the certificate, which is what makes them usable in a submission.
- The tightest coverage band in the Atlas finishing range: 2.5 to 3.0 kg/m², against 2.5 to 5.5 kg/m² for the silicate and acrylic-silicone finishes, so material take-off on a large elevation lands within a much narrower window.
- A key coat that is fixed, not chosen: Atlas Silkon ANX at 0.25 to 0.35 kg/m² is the key coat named for this render, which removes the most common ordering error on a mixed-brand facade.
- Thirty-year certified system life: under normal service conditions, installed and maintained to the certificate, the system is assessed as remaining effective for at least 30 years.
- Two grain sizes: 1.5 to 2.0 mm particle sizes, letting the texture scale match the building without changing the certified build-up around it.
- A documented installer route: the system is installed by contractors trained and registered by the certificate holder, which is the evidence trail warranty providers and Building Control usually ask for.
What BBA 13/5018 Records for This Render
| Property | Certified value and scope |
|---|---|
| Product form | Ready-to-use silicone-silicate-based paste |
| Particle grain sizes | 1.5 to 2.0 mm |
| Coverage | 2.5 to 3.0 kg/m², as a finishing coat of the Atlas/Aval EPS system |
| Coverage per bucket | Approx. 8.3 to 10 m² per 25 kg, derived from the rate above |
| Named key coat | Atlas Silkon ANX, applied at 0.25 to 0.35 kg/m² |
| Reinforcing mesh in the system | Atlas 150, 150 g/m², 4.5 by 5.0 mm grid |
| Basecoat thickness | 2.0 to 5.0 mm, or 4.0 to 6.0 mm with two mesh layers |
| Height restriction, England, Wales, NI | System not for buildings with a storey more than 18 m above ground level |
| Height restriction, Scotland | System not for buildings with a storey 11 m or more above ground level, or 1 m or less from a boundary |
| Certificate | BBA Agrément Certificate 13/5018, Product Sheet 1, fourth issue 25 October 2022 |
| Reaction to fire | Not published — see the note below |
The certificate's reaction-to-fire table classifies complete constructions, and the rows in it name Atlas Cermit Mineral, Atlas Silicate Render, Atlas Silicone Render and Atlas Acrylic-Silicone Render as the finishing coat. None of those rows names this render, so no class is stated for it here, and no class from a neighbouring row is carried across. The same applies to the impact Use Category table, where the row identity could not be resolved cleanly enough to publish.
Atlas publishes a separate product data sheet and Declaration of Performance for this render; neither could be retrieved this session, so no vapour class, Sd figure, water-absorption class, adhesion value, density or DoP number appears above. Ask the Renders World team to supply the current sheet before you submit a specification, and those figures come to you from the manufacturer's own paperwork rather than from a repeated web listing.
How to Apply the Render Over a Reinforced Basecoat
Atlas Silicone-Silicate Render 25kg is supplied ready to use, so there is no mixing ratio and no pot life to manage — stir each bucket to a uniform consistency with a slow-speed paddle and keep the batch sequence consistent across an elevation. The layers underneath it are where the certified figures matter most.
- Adhesive and boards: cementitious powder adhesive at 4.0 to 5.0 kg/m², covering a minimum of 40% of the board, with supplementary mechanical fixings placed while the adhesive is setting.
- Reinforced basecoat: 2.0 to 5.0 mm thick with Atlas 150 alkali-resistant mesh embedded and trowelled smooth, increasing to 4.0 to 6.0 mm where a second mesh layer is specified.
- Key coat: Atlas Silkon ANX at 0.25 to 0.35 kg/m² once the basecoat is dry; the wider exterior render primers range covers the consolidating products used first on high-suction substrates.
- Finish: lay on to a coat thickness matching the grain with a stainless float, then texture with a plastic float while the surface is still workable.
Work wet-on-wet across a whole elevation and plan breaks at corners, downpipes or colour changes so joints fall where the eye expects them. The EWI system build-up guide sets out the full layer sequence, and the step-by-step thin coat render method covers the trowel work in detail.
Installing the Render in UK Conditions — Sequence, Curing and Site Checks
Temperature and humidity limits differ between products in this range, and the limits for this render sit on the Atlas sheet rather than in the certificate, so treat the manufacturer's figures as the governing ones and confirm them before a shoulder-season booking. Protecting the elevation from direct sun, wind and driving rain while the coat cures gives the most uniform finish, particularly on south and west faces where scaffold sheeting earns its keep.
- Check the wall, not the forecast: substrate temperature on a shaded north elevation lags air temperature by a wide margin first thing, and an infrared thermometer settles it in seconds.
- Prepare and prime to the substrate: the substrate preparation guide covers suction testing and consolidation on old lime plaster and aerated block.
- Book the weather window: the seasonal application timing guide maps the UK calendar month by month.
- Keep the certified route intact: the system is designed to be installed by contractors trained and registered by the certificate holder, which keeps the warranty and the certificate working together.
How the Atlas Finishing Coats Compare Inside One Certified System
All three finishes below are named in the same certificate, at the same stage of the same build-up, which makes the comparison a like-for-like one. The key coat column is the practical differentiator, because it changes what else goes on the order.
| Finishing coat | Grain sizes | Certified coverage | Key coat named for it |
|---|---|---|---|
| Atlas Silicone-Silicate Render | 1.5 to 2.0 mm | 2.5 to 3.0 kg/m² | Atlas Silkon ANX |
| Atlas Silicone Render | 1.5 to 2.0 mm | 2.5 to 3.5 kg/m² | Atlas Silkon ANX |
| Atlas Acrylic Render | 1.5, 2.0 and 3.0 mm | 2.5 to 5.0 kg/m² | Atlas Cerplast |
The silicate hybrid carries the narrowest consumption band of the three, so quantity risk on a large contract is lowest here. The acrylic render shares its key coat with the mineral and acrylic-silicone finishes, which is worth knowing if a facade is being finished in more than one material.
Choosing Between This Finish and the Rest of the Range
- Choose this render where the specification is an Atlas EPS build-up, the storey heights sit inside the certificate's limits, and you want the tightest coverage band for take-off purposes.
- Choose a straight silicone finish where the project is standard modern masonry and the extra silicate binder brings nothing the wall needs; the parent collection lists the white and grey bases side by side.
- Settle the colour first — shade and grain both change how a facade reads, and the render colour charts and catalogues let you sign a physical swatch off before the tinting run.
Renders World lists this render at £51.00 per 25 kg bucket as displayed in August 2026, in stock at the time of that check. At the certified 2.5 to 3.0 kg/m², one bucket covers roughly 8.3 to 10 m², which puts material cost at about £5.10 to £6.14 per m² before labour, access or the layers beneath. To price a full elevation or compare the tinted bases, work from the full thin-coat render collection.
FAQ — Coverage, Certification and Heritage Use
How many buckets does a 100 m² elevation take?
Between eleven and fourteen, with waste allowed for. The working is worth showing:
- 100 m² × 2.5 kg/m² = 250 kg; 100 m² × 3.0 kg/m² = 300 kg.
- 250 ÷ 25 = 10 buckets; 300 ÷ 25 = 12 buckets.
- Plus 10% for reveals, cut-outs and detailing: 11 to 14 buckets.
The render coverage calculator runs the same arithmetic across other grains and products.
What else does the certified build-up need?
Atlas Silkon ANX key coat at 0.25 to 0.35 kg/m² directly beneath it, over a reinforced basecoat of 2.0 to 5.0 mm carrying Atlas 150 mesh at 150 g/m². Swapping the key coat for a different one takes the wall outside the certified specification, so order the two together.
What does BBA 13/5018 actually certify?
The Atlas/Aval EPS external wall insulation system as a whole, not this bucket on its own. Certificate limits apply to the system: in England, Wales and Northern Ireland it should not be used on buildings with a storey more than 18 m above ground level, and in Scotland not on buildings with a storey 11 m or more above ground level or within 1 m of a boundary. Confirm the fire strategy for the specific project with the designer.
How does it differ from the plain Atlas silicone render?
On the certified figures, the difference is consumption: 2.5 to 3.0 kg/m² against 2.5 to 3.5 kg/m², over the same grain range and the same Silkon ANX key coat. The binder chemistry differs too, but the vapour and absorption figures that would quantify that sit on the Atlas product sheets, so ask for both sheets if the comparison has to be evidenced in a specification.
Is it the right choice for a listed building?
It is a common candidate on breathable-wall work, and the honest position is that the certificate covers it as part of an insulated system rather than as a heritage coating with a published vapour class. Confirm the requirement with the conservation officer, request the Atlas sheet for the permeability figures, and specify against those two documents together.
Technical Documentation — BBA Agrément Certificate 13/5018