Description
One 25 kg bag of Atlas Hoter U White does two jobs — bonding the boards at 4.0–5.0 kg/m² and forming the mesh-reinforced layer at 3.0–3.5 kg/m² — on a white-cement binder that leaves a bright surface under pale thin-coat finishes and one product line to order instead of two.
Where Atlas Hoter U White Earns Its Place on a Light-Rendered Facade
Specified as the Atlas Hoter U White EPS adhesive basecoat 25kg UK installers use across ETICS elevations, this white-cement mortar bonds EPS, graphite EPS and XPS boards at 4.0–5.0 kg/m² and then embeds the reinforcing mesh. Renders World holds it inside the EPS adhesives basecoats range, beside the grey-cement version built on the same fibre-reinforced formulation.
The binder is the reason to reach for the white bag. Atlas states in the product's data sheet that using white cement increases the strength of the layer formed by the adhesive, and the bright cured surface reads truer under pale finishes than a grey base does. The colour-and-adhesive decision across the whole range is worked through in the EPS adhesive selection guide.
The sheet also names the substrates the mortar was built for, which is the quickest pre-order check on any wall:
- Concrete of all classes and aerated concrete — bonded direct where the face is sound, clean and unfrozen.
- Cement and cement-lime renders — primed first where the existing coat is weak, dusty or highly absorbent, which is the same instruction the sheet gives for aerated concrete and slag-block walls.
- Sandstone and unrendered masonry in brick, block, hollow block and silicate units.
Why Specifiers Choose the White-Cement Version
- Two stages from one bag: the same mortar bonds boards at 4.0–5.0 kg/m² and forms the reinforced layer at 3.0–3.5 kg/m², so a job runs on one product code rather than a separate adhesive and basecoat order.
- White cement raises layer strength: Atlas gives this as the working difference between the two versions, which is why the white bag is chosen where the reinforced layer is doing structural work under a light finish.
- Microfibre reinforcement: the sheet describes a fibre-reinforced mix, cellulose fibres in the data section, giving the cured layer its resistance to cracks and scratches — the property explored in the fibre-enhanced basecoat guide.
- Four-hour pot life, 25-minute open time: a batch mixed at the station stays workable for around 4 hours at the sheet's stated conditions, while the open time governs how much mesh goes in before the wet edge closes.
- Vapour permeable and frost-resistant: Atlas describes the cured mortar as not restricting water vapour flow through the insulated wall, which keeps the drying route open on a solid-wall retrofit.
- A bright base under pale finishes: a white reinforced layer takes the colour-masking job away from the primer, so the primer is chosen for suction control and key, with its coat count read from its own data sheet.
Technical Data From the Atlas Hoter U Data Sheet
Every line describing the Atlas Hoter U White EPS adhesive basecoat 25kg below is transcribed from the Atlas Hoter U technical data sheet, last updated February 2016, which publishes one data table covering both the white- and grey-cement versions. Where that sheet is silent — no reaction-to-fire class, no EN 15824 declaration — this page stays silent too.
| Property | Value from the sheet |
|---|---|
| Product type | 2-in-1 cement mortar: board bonding and mesh embedding |
| Version | White cement (grey-cement version also produced) |
| Reinforcement | Microfibre, given as cellulose fibres |
| Bulk density, dry mix | approx. 1.40 kg/dm³ |
| Density after mixing | approx. 1.55 kg/dm³ |
| Density when set | approx. 1.45 kg/dm³ |
| Water | 5.00–5.50 l per 25 kg (0.20–0.22 l/kg) |
| Maturing time | approx. 5 minutes |
| Pot life | approx. 4 hours |
| Open time | min. 25 minutes |
| Mortar, substrate and ambient temperature | +5 °C to +25 °C |
| Reinforced layer thickness | 2 mm min. / 5 mm max. |
| Adhesion to concrete | min. 0.25 MPa |
| Adhesion to EPS | min. 0.08 MPa |
| Consumption, board bonding | 4.0–5.0 kg/m² |
| Consumption, reinforced layer | 3.0–3.5 kg/m² |
| Insulation thickness bonded | up to 25 cm (see the approval note below) |
| Water-soluble chromium VI | ≤ 0.0002% |
| Shelf life | 12 months from production date, sealed and dry |
| Packaging | 25 kg paper bag; 1050 kg pallet |
Two arithmetic points fall out of that table and are worth having before ordering. A pallet is 1050 kg ÷ 25 kg = 42 bags, and one bag covers 25 kg ÷ 4.0–5.0 kg/m² = 5.0–6.25 m² of board bonding or 25 kg ÷ 3.0–3.5 kg/m² = 7.1–8.3 m² of reinforced layer.
Approval Scope: What Is Certified, and Against Which Version
The data sheet splits its approvals by cement colour, and the split matters on a specified job. Reading the grey version's line against the white bag is the single easiest transcription error on this product, so the two are set out separately here.
- White version: covered by the thermal insulation system approval ATLAS ETICS, AT-15-9090/2014, with factory production control certificate ZKP ITB-0562/Z.
- Grey version: the same ATLAS ETICS approval plus ITB AT-15-6347/2014 and two European Technical Assessments, ETA 06/0081 (ATLAS system) and ETA 07/0316 (ATLAS XPS).
Read as a purchasing instruction: where a specification calls for an adhesive whose own line carries an ETA number, the grey-cement version is the one that satisfies it on paper today. These are Polish national and European system documents rather than UK certification, and under current Approved Document practice it is the complete external wall build-up, not a single bag, that Building Control and a warranty provider assess.
One scope divergence is open on board thickness. The 2016 sheet states insulation up to 25 cm; the current Atlas product page states EPS up to 50 cm and XPS up to 20 cm. The stricter figure is the sheet's 25 cm, so plan to it and confirm anything deeper with Atlas before the boards are ordered.
How to Apply Atlas Hoter U White — Mixing, Bonding and the Reinforced Layer
Mixing the 25 kg bag
Pour the powder into a measured 5.00–5.50 litres of clean water, mix with a paddle drill to a uniform consistency, leave it to mature for about 5 minutes and remix. Prepared mortar is used within roughly 4 hours, so batch to what the bay actually takes.
Bonding the boards
- Lay a continuous perimeter band at least 3 cm wide around the board edge.
- Add 6–8 dabs of 8–12 cm diameter spread evenly across the face.
- Apply enough mortar to cover at least 40% of the board, rising to a minimum of 60% once the board is pressed home.
- Press to line so the mortar under the board is no more than 1 cm thick; on flat, even walls a notched trowel spreading a 2–5 mm layer across the whole face is the alternative the sheet allows.
The mesh-reinforced layer
The reinforced layer starts once the bonding mortar has set and any mechanical fixings are in — on average three days, which is longer than the day-one turnaround some programmes assume, and worth building into the schedule. Comb the mortar onto the boards, bed Atlas 150 g/m² reinforcing mesh in vertical strips as Atlas recommends, and skim smooth so the mesh is invisible and never touching the board face.
Sand and de-dust graphite boards before this layer goes on, since the sheet asks for it specifically on graphite EPS. Thin-coat rendering follows no earlier than three days after the reinforced layer, and the basecoat and mesh reinforcement guide carries the overlap and corner detailing in full.
Installation Notes: Conditions, Curing and Site Handling
Conditions do most of the work on a cement mortar, and the sheet is specific about them. Holding mortar, substrate and ambient temperature between +5 °C and +25 °C and sheeting the scaffold gives the layer the steady set it was formulated for.
- Keep graphite boards cool: Atlas asks that heated graphite EPS is not bonded and not allowed to warm during fitting or initial set, so shaded elevations and early starts protect the bond — the same discipline applies to the graphite EPS insulation boards stocked here.
- Stand down in rain, snow or strong wind: the sheet rules those conditions out, and scaffold sheeting keeps a marginal day workable.
- Test a doubtful substrate: bond 8–10 EPS cubes of 100 × 100 mm at points across the elevation and check them after three days — if the polystyrene tears, the wall is carrying; if a cube lifts with the mortar and a layer of substrate, the specification needs the weak layer dealt with first.
- Fixing quantity is a system figure: the number of anchors per square metre comes from the system holder and the wind-load calculation, not from the adhesive sheet, and the method sits in the insulation board fixing pattern and spacing guide.
- Clean tools with water immediately: hardened residue comes off with an Atlas cleaning agent, which saves a set of floats on a long day.
Seen as one wall rather than one bag, the mortar appears twice in the build-up — under the boards and over them — which is why it sets the programme between board day and render day. The EWI system build-up guide puts both appearances in sequence with the layers either side.
Atlas Hoter U White Against the Grey Variant and the Wool Route
Both Hoter U versions share one data table, so the choice is not a performance trade-off; it is binder colour, approval paperwork and price. Renders World also stocks a separate wool-and-EPS adhesive for slab build-ups, which is a different job again.
| Option | What the documents say | When to choose it |
|---|---|---|
| Atlas Hoter U White 25 kg | White cement, stated to increase layer strength; ATLAS ETICS AT-15-9090/2014 | Pale and pastel finishes, and where a brighter reinforced layer is wanted |
| Atlas Hoter U Grey 25 kg | Same data table; approval line adds ETA 06/0081 and ETA 07/0316 | Mid and dark finishes, and specifications that ask for an ETA against the adhesive |
| Slab build-ups in mineral wool insulation | Hoter U is written for EPS, graphite EPS and XPS only | Stone wool facades, which take the wool-rated adhesive listed with that range |
Is the White Version Right for Your Build-Up?
- Yes, for pale thin-coat schemes on EPS or XPS: one bag covers both stages, and the white reinforced layer sits brighter under a light finish.
- Costed per square metre: at £13.90 per 25 kg bag, August 2026, board bonding works out at £13.90 ÷ 5.0–6.25 m² = £2.22–£2.78/m², and the reinforced layer at £13.90 ÷ 7.1–8.3 m² = £1.67–£1.95/m², using the sheet's own consumption ranges.
- Dark or mid-tone finish? The grey-cement Hoter U runs on the identical data table and is the sensible spec where the base colour never shows.
- Buying the mesh with it: the reinforcing layer needs a roll matched to the system, and both grades sold here sit in the fibreglass mesh range.
- Ready to order: the Atlas Hoter U White EPS adhesive basecoat 25kg bag was showing in stock at the August 2026 fetch, in single bags or by the 42-bag pallet.
FAQ — Coverage, Curing and Ordering
How many bags does 100 m² of external wall insulation take?
Board bonding at 4.0–5.0 kg/m² gives 100 × 4.0–5.0 = 400–500 kg, which is 400–500 ÷ 25 = 16–20 bags. The reinforced layer at 3.0–3.5 kg/m² gives 300–350 kg, or 12–14 bags. Total 28–34 bags, and adding a 10% site allowance for uneven walls and offcuts brings the order to 31–38 bags.
Which boards can it bond?
Atlas writes it for expanded polystyrene including graphite and elasticised grades, and for extruded polystyrene. The sheet gives a bonded insulation thickness of up to 25 cm while the current Atlas product page quotes EPS up to 50 cm and XPS up to 20 cm, so plan to the stricter 25 cm and confirm deeper build-ups with the manufacturer.
Is the white version stronger than the grey?
Atlas states that white cement increases the strength of the layer, but publishes one adhesion table for both versions — min. 0.25 MPa to concrete and min. 0.08 MPa to EPS. Treat the difference as binder colour and layer quality rather than a higher declared bond figure, and note that the ETA numbers appear on the grey version's approval line.
What conditions does it need on the day?
Mortar, substrate and ambient temperature all sit between +5 °C and +25 °C, with no application during rain, snow or strong wind and scaffold sheeting in place. Mixed mortar stays workable for about four hours, and the 25-minute open time is the figure that really governs how much mesh goes in per pass.
How long do unopened bags keep?
Twelve months from the production date printed on the bag, stored sealed and dry, ideally on a pallet clear of the ground. Bags that stay wrapped until the elevation is ready reach the wall performing exactly as the data sheet describes.
Is it certified for UK use?
The white version's documented cover is the Polish ATLAS ETICS system approval AT-15-9090/2014 with factory production control certificate ZKP ITB-0562/Z, which is a system document rather than a UK product certification. For UK compliance the assessed item is the whole external wall build-up, so specify the adhesive as part of a system and keep the manufacturer's documents with the project file.
Technical Documentation