Description
Atlas Roker U Grey is the dual-rated cementitious adhesive and basecoat that bonds mineral wool slabs up to 300 mm and EPS boards up to 500 mm from a single 25 kg bag, then embeds fibreglass mesh into the same reinforcement layer — the one specification that lets UK installers run mixed wool-and-EPS facades without switching adhesive between board types.
Where Atlas Roker U Performs Best — Mixed Wool and EPS Elevations
Atlas Roker U is a polymer-modified cementitious mortar that carries certification for both mineral wool and EPS within the Atlas ETICS system under ETA-06/0173, achieving ≥ 0.25 MPa adhesion to concrete and ≥ 0.08 MPa to both wool and polystyrene from one mix. Most adhesives in the EPS adhesives and basecoats range are board-type-specific; Roker U is the dual-rated option that lets one bag code cover the whole facade.
The product belongs on projects where wool and polystyrene meet on the same building. A typical case is a residential block running a non-combustible wool fire break at each storey above 18 m while EPS handles the field elevations, or a solid-wall Victorian terrace where painted brick and bare stock brick alternate and the adhesive needs to grip both. It also suits any contractor who wants one universal adhesive across insulation grades rather than ordering separate products — so procurement stays simple and the wrong bucket never lands on the wrong elevation.
Why Trade Specifiers Choose Atlas Roker U
- Wool to 300 mm, EPS to 500 mm in one product: The same 25 kg bag handles mineral wool slabs up to 300 mm and polystyrene boards up to 500 mm, covering practically every UK retrofit and new-build thickness across both board types without switching adhesive.
- Certified bond on three substrates: Tested at ≥ 0.25 MPa to concrete and ≥ 0.08 MPa to both wool and EPS, so the adhesive performs at certification level on every interface a mixed-insulation facade presents.
- High-rise specification path: Paired with mineral wool slabs and the correct fixing density, Roker U sits within the certified fire-strategy envelope on tall residential buildings where current UK guidance calls for non-combustible insulation above 18 m.
- Highly vapour permeable: Engineered to match the breathability of the wool layer, so moisture moves outward through the system rather than building up at the adhesive line — the property that keeps a wool build-up dry.
- Structural micro-fibre reinforcement: Fibres run through the cured matrix and bridge hairline fractures during the first 24–48 hours of cure, when most shrinkage cracking forms — the fibre-enhanced basecoats guide explains the full mechanism.
Technical Specifications — Atlas Roker U Data Sheet Highlights
| Property | Value |
|---|---|
| Product type | Polymer-modified cementitious adhesive and reinforcing mortar (2-in-1) |
| Pack size | 25 kg bag |
| Mixing ratio | 5.50–6.00 L clean water per 25 kg |
| Pot life | ~ 2 hours at 20 °C |
| Open time | Min. 30 minutes |
| Application temperature | +5 °C to +30 °C (substrate and ambient) |
| Board fixing — EPS | 4.0–5.0 kg/m² |
| Board fixing — mineral wool | 4.5–5.5 kg/m² |
| Basecoat layer — EPS | 3.0–5.0 kg/m² (2–5 mm) |
| Basecoat layer — mineral wool | 5.5–6.5 kg/m² (4–6 mm) |
| Adhesion to concrete (air-dry) | ≥ 0.25 MPa |
| Adhesion to EPS / mineral wool | ≥ 0.08 MPa |
| Max board thickness — EPS / wool | 500 mm / 300 mm |
| System certification | Atlas ETICS · ETA-06/0173 |
| Shelf life | 12 months, sealed, dry storage |
How to Apply Atlas Roker U — Mixing, Two-Stage Wool Bonding, Mesh Embedding
Mix the 25 kg bag into 5.5–6.0 litres of cool, clean water on a low-speed paddle until lump-free, rest the paste for five minutes, then remix to activate the polymers. For EPS boards, apply a 3–4 cm perimeter band with three to six central dots, then press the board home until adhesive contact covers at least 40 % of the rear face.
Mineral wool needs a different technique, because its fibrous surface must be keyed rather than coated. Apply a thin scrape coat onto the board's rear face first, working the mortar into the surface fibres with the trowel edge, then apply the full adhesive bed over that keyed layer. This two-stage method is what delivers the certified ≥ 0.08 MPa pull-off on wool — a single heavy pass over unprepared fibres bonds far more weakly.
Once the bonding layer has cured and mechanical fixings are set, trowel a continuous basecoat at the right thickness for the board, embed Atlas 150 g/m² fibreglass mesh with minimum 100 mm overlaps, and smooth a second thin pass over the top. The basecoat and mesh reinforcement guide covers overlap discipline and corner detailing.
Installation Notes — Conditions, Drying Times, High-Rise Considerations
Roker U cures best between +5 °C and +30 °C, with substrate and ambient temperatures inside that range for at least 24 hours after application. The higher upper limit than standard EPS adhesives reflects the product's use on tall buildings, where solar gain pushes south-facing substrate temperatures up.
On high-rise wool work, fixing density typically rises to 8 anchors per m² rather than the 6 per m² common on low-rise EPS, reflecting the heavier slab and greater wind load at height. Schedule the basecoat pass for overcast conditions or shaded scaffolding where you can, since direct sun on a fresh 4–6 mm wool basecoat flash-dries the surface before the mesh embeds cleanly. Allow the basecoat a minimum three-day cure before priming and applying the decorative render.
Pro Tips From UK Installers Using Atlas Roker U
These are the working habits that make a mixed-board elevation run smoothly with Roker U across the whole facade.
- Scrape-coat the wool the day before where programme allows — a coat left to firm overnight gives the strongest key the next morning, so the full bed goes onto a dust-locked surface.
- Number the wool boards before scrape-coating — wool boards look identical, and keeping them in sequence preserves the factory edge alignment that holds joints tight.
- Order against the wool area first — the 5.5–6.5 kg/m² wool basecoat rate is roughly double the EPS rate, so sizing the bag count on the wool zones keeps you from running short mid-elevation.
- Keep one adhesive top to bottom — the labour saving of a single product across the whole facade, plus removing wrong-bucket risk, usually outweighs the material cost difference on jobs above 200 m².
Is Atlas Roker U Right for Your Project?
Roker U is the right call when the elevation uses mineral wool, EPS, or a mix of both on the same building, and you want one certified adhesive and basecoat across the whole facade. The table below shows how it sits against the two EPS-specific siblings in the Renders World range so you can match the product to your board specification.
| Variant | Key Spec | When to Choose |
|---|---|---|
| Atlas Hoter U Grey | EPS-only, fibre-enhanced, grey | EPS field walls, mid/dark finish |
| Atlas Roker U Grey | Wool 300 mm + EPS 500 mm, dual-rated | Mixed wool-and-EPS facades |
| Atlas Hoter U White | EPS-only, white cement, 2-in-1 | EPS with pale or white render |
- For the board decision itself, the mineral wool vs polystyrene comparison weighs fire performance, thermal conductivity, and cost per m² across both board types.
- For high-rise fire-strategy context, the Building Safety Act 2026 facade fire requirements guide sets out how non-combustible insulation interacts with current UK guidance above 18 m.
- Pair the boards to match — Renders World stocks compatible mineral wool slabs and EPS insulation boards that carry the same ETA system certification.
FAQ — Atlas Roker U Coverage, Compatibility, High-Rise Specification
Common specification and ordering questions from installers running Roker U across mixed-board elevations.
How many bags of Roker U do I need per 100 m² of mixed elevation?
Calculate each zone separately, because coverage differs by board. EPS at typical rates (4.5 kg/m² fixing plus 4.0 kg/m² basecoat) uses roughly 850 kg or 34 bags per 100 m²; wool at typical rates (5.0 kg/m² fixing plus 6.0 kg/m² basecoat) uses around 1,100 kg or 44 bags. Sum the two by zone size and add 10 % for wastage — order against the wool-zone area rather than averaging across the facade.
Is Roker U certified for high-rise buildings above 18 metres?
Within the Atlas ETICS system under ETA-06/0173, the wool-and-Roker U combination is the route that current UK fire guidance permits on tall residential buildings requiring non-combustible insulation. For EPS-based build-ups, standard height provisions in the ETA documentation apply, and the project fire strategy remains the governing reference for any specification decision at height.
Why does mineral wool need a two-stage application when EPS does not?
Wool's fibrous surface absorbs adhesive unpredictably if the full bed goes on in one pass, so a thin scrape coat is keyed in first to create a dense, even contact layer that the main bed bonds to reliably. EPS has a closed surface that accepts adhesive cleanly in a single pass, so the scrape stage adds nothing on polystyrene. On wool, the two-stage discipline is what delivers the certified ≥ 0.08 MPa pull-off strength.
Do I still need mechanical fixings on wool installations?
Yes, and at higher density than EPS work — typically 8 anchors per m² on wool versus 6 per m² on standard EPS, reflecting the heavier slab and greater wind load. Install the fixings through the boards once the bonding layer has fully cured, then apply the reinforced basecoat over the anchor heads so they are fully encapsulated.
Does the substrate need priming before applying Roker U?
Dense, well-cured concrete and clean fair-faced brick generally accept the adhesive directly, giving the fastest programme. Absorbent, dusting, or chalky substrates should be sealed with a wall primer first so suction is even and the mortar cures at full strength. Well-bonded existing paint usually accepts Roker U without primer thanks to the elevated polymer content, though a tap-test on suspect paint zones is worth doing on Victorian and Edwardian elevations.
Written by Mariusz Saja. Technically reviewed by Rafał Wyrzykowski. Last reviewed Jul 2026.
Technical Documentation — Atlas Roker U TDS and System Certificate