ROKER U GREY ADHESIVE WOOL & EPS 25kg

Atlas Roker U Grey 25 kg is the dual-rated cementitious adhesive and basecoat that bonds mineral wool slabs up to 300 mm and EPS boards up to 500 mm to masonry substrates, then embeds fibreglass mesh into the reinforcement layer — delivering ≥ 0.25 MPa adhesion to concrete and ≥ 0.08 MPa to both wool and polystyrene from the same mix. Sold within the professional EPS adhesives and basecoats range at Renders World, Roker U is the specification that lets UK installers run mixed-insulation facades — wool on the fire-break zones, EPS on the field elevations — without changing adhesive between board types or risking material incompatibility at the elevation junctions.

Where Atlas Roker U Performs Best — Mixed Wool and EPS Elevations

Atlas Roker U is a polymer-modified cementitious mortar engineered for two duties in one product — bonding insulation boards to mineral substrates and embedding fibreglass mesh into the reinforced basecoat layer — with the unusual property of carrying full certification for both mineral wool slabs and EPS insulation boards within the Atlas ETICS system under ETA-06/0173. Most adhesives in the category are board-type-specific; Roker U is the dual-rated option that lets one bag code cover the whole job.

The product belongs on projects where mineral wool and polystyrene meet on the same building — typically high-rise residential blocks where a non-combustible wool fire break runs at every storey above 18 m while EPS handles the field walls, or solid-wall Victorian terraces where painted brick and bare stock brick alternate across elevations and the adhesive needs to grip both. It also suits any specification where the contractor wants to simplify procurement by carrying one universal adhesive across multiple insulation grades rather than ordering separate products and risking the wrong bucket 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 thick and polystyrene boards up to 500 mm thick — covering practically every UK retrofit and new-build insulation thickness across both board types without switching adhesive.
• ≥ 0.25 MPa to concrete, ≥ 0.08 MPa to both wool and EPS: Tested bond strength on three substrate types within the same product means the adhesive performs at certification level on every interface that a mixed-insulation facade presents.
• High-rise certification path: Roker U is the adhesive that enables the Atlas wool-based system on tall residential buildings where current UK fire guidance specifies non-combustible insulation above the 18-metre height threshold — when paired with mineral wool slabs and the correct mechanical fixing density, the build-up sits within the certified fire-strategy envelope.
• Highly vapour permeable: Critical when bonding mineral wool, which depends on outward vapour transmission to stay dry — Roker U is engineered to match the breathability of the wool layer so moisture moves out through the system rather than building up at the adhesive line.
• Structural micro-fibre reinforcement: The cured mortar carries fibres throughout the matrix that bridge hairline fractures during the first 24–48 hours of cure, when most shrinkage cracking forms — see the fibre-enhanced basecoats guide for the full mechanism.
• Strong grip on difficult substrates: Elevated polymer dispersion content delivers reliable adhesion on well-bonded painted masonry, older brickwork, and mixed-substrate Victorian elevations where standard adhesives sometimes need a separate bonding primer first.

Technical Specifications — Atlas Roker U Data Sheet Highlights

Property	Value
Product type	Polymer-modified cementitious adhesive and reinforcing mortar (2-in-1)
Composition	Cement binder, mineral aggregates, polymer dispersions, micro-fibres
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 thickness)
Basecoat layer — mineral wool	5.5–6.5 kg/m² (4–6 mm thickness)
Adhesion to concrete (air-dry)	≥ 0.25 MPa
Adhesion to EPS (air-dry)	≥ 0.08 MPa
Adhesion to mineral wool (air-dry)	≥ 0.08 MPa
Max board thickness — EPS	500 mm
Max board thickness — mineral wool	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 using a paddle mixer on low speed until lump-free, rest the paste for five minutes, then briefly remix to activate the polymers. For EPS and XPS boards, apply the mortar in a 3–4 cm perimeter band with three to six central dots, then press the board against the wall until adhesive contact covers at least 40 % of the rear face.

For mineral wool, the bonding technique changes — wool's fibrous surface needs the adhesive to mechanically key into the fibres rather than sitting on top of them. Apply a thin scrape coat directly onto the board's rear face, working the mortar into the surface fibres with the trowel edge and letting that contact layer firm up briefly. Then apply the full adhesive bed using the perimeter-and-dot or notched-trowel method over the keyed scrape coat. This two-stage approach is what delivers the certified ≥ 0.08 MPa pull-off strength on wool — a single heavy pass over an unprepared fibrous surface gives a much weaker bond.

After the bonding layer has cured (typically 24 hours) and mechanical fixings are installed, trowel a continuous basecoat layer at the correct thickness for the board type (2–5 mm on EPS, 4–6 mm on wool), press Atlas 150 g/m² fibreglass mesh into the wet mortar with minimum 100 mm overlaps, and smooth a second thin pass over the top. The complete basecoat and mesh reinforcement layer guide covers overlap discipline, corner detailing, and the diagonal patches around openings.

Installation Notes — Conditions, Drying Times, High-Rise Considerations

Atlas Roker U cures best between +5 °C and +30 °C, with both substrate and ambient temperatures inside that range for at least 24 hours after application. The wider upper temperature limit compared to standard EPS adhesives (+30 °C rather than +25 °C) reflects the product's intended use on tall buildings where solar gain on south-facing elevations pushes substrate temperatures higher than on typical low-rise work.

On high-rise wool installations, the mechanical fixing density typically rises to 8 anchors per square metre rather than the 6 anchors per m² common on low-rise EPS — the slab weight is higher and the wind-load pressures at height are substantially greater. Schedule the basecoat pass for overcast conditions or shaded scaffolding where possible, since direct midday sun on a freshly applied 4–6 mm wool basecoat will flash-dry the surface before the mesh is properly embedded. Allow the finished basecoat to cure for a minimum of three days before priming and applying the decorative thin-coat render.

Pro Tips From UK Installers Using Atlas Roker U

• Scrape-coat the wool the day before, where programme allows. A scrape coat applied late afternoon and allowed to firm up overnight gives the strongest mechanical key the next morning — the full adhesive bed goes on a properly prepared, dust-locked surface rather than chasing the same operation in one continuous pass under pressure.
• Mark the wool boards before scrape-coating. A pencil number on each wool board before the scrape coat is applied lets the crew place them in sequence on the wall without confusion — wool boards look identical and out-of-sequence placement loses the factory edge alignment that holds the joint tight.
• Watch consumption on the wool basecoat. The 5.5–6.5 kg/m² rate on wool basecoat is roughly double the EPS rate — order the bag count against the wool surface area first, not against the cheaper EPS rate, or the wool zones run short halfway through the elevation.
• Use the same product top to bottom. The temptation on a mixed-board job is to use a cheaper EPS-only adhesive on the field walls and Roker U only on the wool zones — the labour saving from one adhesive across the whole elevation, plus the elimination of wrong-bucket risk, usually outweighs the material cost difference on jobs above 200 m².

Is Atlas Roker U Right for Your Project?

• Atlas 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 rather than two board-specific products with the procurement and on-site sequencing risk that comes with split specification.
• EPS-only specification with mid- or dark-tone finish? Switch to Atlas Hoter U Grey 25 kg — the polystyrene-specific 2-in-1 adhesive at a lower price point per bag, ideal when wool compatibility is not required by the fire strategy.
• EPS-only with pale or white finish? The white-cement sibling Atlas Hoter U White 25 kg reduces tinted-primer requirements under light renders — the better commercial pick on pale-finish EPS jobs where wool compatibility is not part of the spec.
• For the wool-vs-EPS decision in detail, the mineral wool vs polystyrene comparison covers fire performance, thermal conductivity, moisture handling, and cost-per-m² side by side 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 specification interacts with current UK regulatory guidance above the 18-metre threshold.
• For full-system specification, the EPS adhesive and basecoat selection guide maps every product in the range to the substrate and board scenario where it performs best.

FAQ — Atlas Roker U Coverage, Compatibility, High-Rise Specification

How many bags of Roker U do I need per 100 m² of mixed wool and EPS elevation?

Coverage rates differ by board type, so calculate each zone separately. On EPS at typical rates (4.5 kg/m² fixing + 4.0 kg/m² basecoat), 100 m² consumes around 850 kg or 34 bags. On wool at typical rates (5.0 kg/m² fixing + 6.0 kg/m² basecoat), the same area consumes around 1,100 kg or 44 bags. For a mixed elevation, sum the two figures by zone size and add 10 % for wastage — wool zones drive consumption noticeably higher and order quantities should reflect the wool-zone area rather than averaging across the whole facade.

Is Roker U certified for high-rise residential buildings above 18 metres?

Within the Atlas ETICS system under ETA-06/0173 there is no height restriction on Roker U when paired with mineral wool slabs — the wool-and-Roker U combination is the route that current UK fire guidance permits on tall residential buildings where non-combustible insulation is required. For EPS-based build-ups, standard height restrictions apply as set out in the relevant ETA documentation, and the fire strategy for the specific project remains the governing reference for any specification decision above 11 metres or 18 metres.

How long does the mixed mortar stay workable in the bucket?

At 20 °C the mixed paste stays workable for approximately two hours — shorter than some 4-hour cement adhesives in the range, so plan batch sizes accordingly. In warm weather above 25 °C the working time shortens noticeably, and on a hot day mixing should be limited to what the crew can apply within 60–90 minutes rather than the full 2-hour pot life.

Why does mineral wool need a two-stage application when EPS does not?

Mineral wool's fibrous surface absorbs adhesive into the fibre matrix unpredictably if the full bed goes on in one pass — a thin scrape coat applied first mechanically keys the mortar into the surface fibres and creates a dense, even contact layer that the main adhesive bed then bonds to predictably. EPS has a closed surface that accepts adhesive cleanly in a single pass, so the scrape stage adds no value on polystyrene. The two-stage approach on wool is the discipline that 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. Typical specifications call for 8 anchors per square metre on mineral wool versus 6 anchors per m² on standard EPS, reflecting the higher slab weight and the greater wind-load pressures on the elevations where wool is commonly specified (tall buildings, exposed coastal sites). Install the fixings through the boards after 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. Absorbent, dusting, or chalky substrates — aerated concrete blocks, weathered lime renders, chalky older brick — should be sealed with a wall primer beforehand so suction is even and the mortar cures at full strength rather than drying out into the substrate. Well-bonded existing paint generally accepts Roker U without primer thanks to the elevated polymer dispersion content, but a tap-test on suspect paint zones before specification is worth doing on Victorian and Edwardian elevations.

Technical Documentation — Atlas Roker U TDS and System Certificate

• Atlas Roker U — Manufacturer Technical Data Sheet (PDF, atlas.com.pl)
• Atlas Roker System — European Technical Assessment ETA-06/0173 (PDF, atlas.com.pl)
• Atlas Roker U — Product Page and Declaration of Performance (atlas.com.pl)