Description
Repair and levelling sit one stage before bonding, and treating them as the same job costs a day on site. Atlas ZW 330 belongs to that first stage, and Renders World stocks it in the EPS adhesives basecoats collection alongside the bonding and reinforcing mortars that follow it.
Where Atlas ZW 330 Earns Its Place on a UK Repair and Levelling Job
Atlas ZW330 fast setting levelling mortar 25kg fills cavities and flattens masonry from 3 mm to 30 mm in one pass, giving tile, render primer or board adhesive a sound plane to bond to. That range is the reason a single bag code covers work a plasterer would otherwise split across two materials.
The manufacturer's own purpose list is unusually specific, and it reads like a refurbishment schedule rather than a marketing page.
- Corner and edge reconstruction — balcony slab edges, beam and column corners, and stair nosings rebuilt back to line.
- Chases and penetrations — grooves left by decommissioned services in walls and floors, and masonry made good where pipes pass through.
- Window reveals — reveal repair when joinery is replaced, which is the detail that decides how the following substrate preparation goes.
- Full-surface levelling up to 30 mm, including thick-layer work reinforced with fibreglass mesh rolls where the sheet calls for added surface reinforcement.
- Falls and facets — shaping slopes into linear drains, terraces and balconies before waterproofing.
Declared substrates are cement and cement-lime plaster, concrete, aerated concrete, cement screeds, and unplastered brick or ceramic and silicate block walls. Declared finishing layers are ceramic tile, plaster, thin-layer render and floor panels, which places the mortar squarely underneath the decorative stages rather than among them.
ZW 330 Technical Data — Strength, Layer Thickness and Set Times
Every figure below is transcribed from an Atlas technical data sheet fetched this session. Where the two editions differ, the section after this one sets them side by side.
| Property | Declared value |
|---|---|
| Layer thickness, single pass | 3 mm to 30 mm |
| Layer thickness, bulked | 31–60 mm, quartz sand ≤2 mm at 1:4 sand to dry mortar by weight |
| Maximum aggregate | 1.0 mm |
| Mixing water | 0.17–0.22 l per kg, or 4.25–5.5 l per 25 kg bag |
| Bulk density, dry mix | approx. 1.6 kg/dm³ |
| Pot life | approx. 2 hours |
| Open time | min. 20 minutes |
| Compressive strength | min. 20.0 MPa |
| Flexural strength | min. 4.0 MPa |
| Screed classification, EN 13813 | CT-C20-F4, interior use |
| Reaction to fire | A1 as a mortar; A1fl in its EN 13813 screed use |
| Tiling after | 5 h at 5 mm · 10 h at 10 mm · 20 h at 20 mm · 48 h above 20 mm |
| Panels, and full load | 48 hours; full load after 3 days |
| Working temperature | +5 °C to +25 °C, mortar, substrate and air |
| Consumption | approx. 15 kg dry mix per m² per 10 mm of thickness |
| Shelf life | 12 months, sealed and dry |
The set times are quoted at approximately 23 °C and 50% humidity, not at 20 °C, and cooler or damper conditions extend them — a point worth carrying into a UK programme, where a 20 mm fill made late on an autumn afternoon is comfortably a next-day return. The A1 classification belongs to the mortar itself and is not the class of a finished wall build-up.
How to Mix and Apply ZW 330 — Water Ratio, Pot Life and Coverage
The sequence is short, and the substrate work at the start carries most of the result.
- Clean back to sound material. Dust, lime, oil, grease, wax, bitumen and paint residues come off, and weak fragments are chiselled away.
- Moisten to a matt-damp state immediately before application — damp, not running wet, so suction is even across the elevation.
- Apply a contact coat where adhesion needs improving, and always for a bonded screed. The sheet specifies a brushed liquid coat worked hard into the damp substrate, then the mortar applied wet on wet.
- Mix into measured water at 4.25–5.5 litres per 25 kg bag with a slow-speed paddle until uniform, and plan the batch around the two-hour pot life.
- Trowel on in layers up to 30 mm, then float with felt or polystyrene after initial set — or leave it deliberately rough where tiling follows.
Coverage runs at approximately 15 kg per m² per 10 mm, so a 25 kg bag of the ZW330 fast setting levelling mortar 25kg gives 25 ÷ 15 = 1.67 m² at 10 mm, or 25 ÷ 7.5 = 3.33 m² at 5 mm. Renders World lists the bag at £11.30, August 2026, and at that rate the material cost works out at £11.30 ÷ 1.67 = £6.78 per m² at 10 mm and £11.30 ÷ 3.33 = £3.39 per m² at 5 mm. VAT treatment is not shown in the live product record, so this page states nothing about it.
Installation Sequence — Deep Fills, Corners and the Break Between Layers
Two instructions on the current sheet are easy to miss and both change how a deep repair is programmed.
- Successive layers need roughly a day between them. Where a cavity is filled in stages rather than in one pass, the sheet sets a technological break of about 24 hours — so a deep rebuild is planned across two visits and comes out stronger for it.
- Sand bulking trades strength for depth. The 1:4 blend takes a fill to 60 mm, and the national assessment figures show the cost: compressive strength moves from ≥22 MPa unsanded to ≥20 MPa sanded, with a longer set. Keep the neat mortar wherever 30 mm will do.
- Protect the fresh surface from rain, sun and drying wind, misting it or covering it with sheeting as needed — even curing is what delivers the declared shrinkage of ≤0.1 mm/m at three days and ≤0.7 mm/m at twenty-eight.
- Screeds get bay discipline. Fields are held to 36 m² with no side over 6 m, isolated from walls with joint profile, with foot traffic after 8–10 hours and full load at three days.
- Clean tools with water immediately. Set residues are removed with a dedicated cement remover, which Renders World stocks in the cleaning range.
Once the plane is true and cured, the build-up moves on: adhesive, boards, a mesh-reinforced basecoat and a decorative coat, in the order set out in the EWI build-up layer guide. Graphite-enhanced EPS insulation boards follow on an insulated elevation, and the adhesive selection guide covers which bonding mortar suits which board. Where the repair carries mesh through a thick section, the reinforcement layer guide sets the overlap discipline, and the same care is what designs out the movement cracking described in the guide to render cracking.
Two ATLAS Data Sheet Editions Disagree — What to Order Against
The 2015 and 2022 editions of the ZW 330 sheet are both in circulation among UK distributors, and they do not carry the same declared values. The divergence is itself useful information, so it is published rather than averaged away.
| Property | 2015 edition | 2022 edition |
|---|---|---|
| Adhesion, EN 998-1 | 0.6 N/mm², FP:B | 0.3 N/mm², FP:B |
| Compressive strength | min. 20.0 MPa | class C20; ≥22 MPa unsanded, ≥20 MPa sanded under ITB-KOT |
| Frost resistance | ≤15% strength loss, 25 freeze-thaw cycles | ≤10% strength loss under ITB-KOT |
| Water vapour, μ | 15/35, tabular value | μ ≤ 30 |
| Contact coat product | ZW 330 with elastic emulsion, or Atlas Adher | Atlas Adher S |
| Approval reference | DoP 167/CPR; ITB AT-15-9437/2015 | DoP 167/2/CPR; ITB-KOT-2019/1202 ed. 1 |
This page leads on the lower declared adhesion of 0.3 N/mm² and the more conservative frost figure, so a specification written from it holds whichever sheet a certifier produces. Where a submission needs a declared value in writing, ask for the declaration of performance covering the batch on order — the 2022 edition states that it voids all previous sheets, and the higher adhesion figures in the national assessment apply only where the contact coat is used.
Is ZW 330 the Right Layer for Your Wall?
- Yes, for cavities, corners and out-of-plane masonry between 3 mm and 30 mm, where the next trade wants a flat, load-bearing plane the same day or the next morning.
- Yes, outdoors — the mortar is declared for external walls, columns and floors, with frost resistance measured over 25 freeze-thaw cycles.
- Deviations under 3 mm? A structural repair mortar is more than that tolerance needs, and a finishing skim gives a smoother base for the decorative layer.
- Boards going on next? The bonding stage is a different product with different certification, and the adhesive and basecoat mortars at Renders World cover it.
Stock and price sit at the top of this page, and the bag adds to the basket directly — a 25 kg lift, worth counting into pallet and access planning where the repair schedule runs to several bays.
FAQ — ZW 330 Coverage, Timings and Ordering
How many bags does a repair take?
Work from 15 kg per m² per 10 mm of thickness. A 10 mm levelling coat over 12 m² needs 12 × 15 = 180 kg, and 180 ÷ 25 = 7.2 bags, so eight covers it with a margin for irregular substrate where the true average depth is hard to judge. At £11.30 per bag as displayed in August 2026, that is a material cost you can quote before the scaffold goes up.
How soon can the next trade load the surface?
Tiling starts after 5 hours at 5 mm, 10 hours at 10 mm, 20 hours at 20 mm, and 48 hours above 20 mm, measured at approximately 23 °C and 50% humidity. Floor panels go down at 48 hours and full load is 3 days, with cooler or damper weather stretching all of it.
Does the substrate need a contact coat or a primer?
A contact coat is specified wherever adhesion needs improving and always under a bonded screed, and the national assessment's higher adhesion figures are quoted on that basis. Separately, both sheet editions recommend priming the cured repair with an Atlas emulsion primer before tiling, which is a distinct step from the contact coat beneath it.
What are the weather limits for exterior work?
Mortar, substrate and air all need to sit between +5 °C and +25 °C during the work, and the fresh surface is protected from rain, strong sun and drying wind while it sets. UK shoulder-season scheduling suits balcony, plinth and stair repairs well, with the 24 hours after application planned to stay comfortably above the lower limit.
What is declared for fire and for site handling?
Reaction to fire is declared A1 for the mortar and A1fl in its screed use, which is a classification of this product and not of any wall assembly built over it. The mix contains cement, so gloves, eye protection and a dust mask during powder handling are the standard precautions, and the safety data sheet governs.
Technical Documentation — ATLAS ZW 330 Data Sheets