Description
Mosaic render is a ground-level material, and the 25 kg bucket is the pack for a continuous run of it. This is the larger of the two packs in the mosaic render range at Renders World, and both carry the same formulation.
What the 25 kg Bucket Is Specified For — Plinths, Reveals and Entrance Details
Ceresit CT177 mosaic render 25kg is a 1.0–1.6 mm coloured-quartz plaster declared to EN 15824, specified on plinths, reveals and door jambs where a facade collects dirt and knocks at ground level.
The manufacturer's own application list is narrower and more useful than "decorative finish" suggests, and it splits cleanly between outdoor and indoor work.
- Outdoors — surfaces that soil quickly: plinths, balustrades, and window and door jambs.
- Indoors — walls exposed to abrasion and dirt, named on the sheet as entrances, corridors and staircases.
- Over insulation — as a facade layer inside the Ceresit Ceretherm systems the sheet assesses, which is where the plinth zone of an insulated wall is finished.
- Bridging fine substrate cracking — the sheet credits the material with bridging hair-like cracks already present in the substrate.
- Below the plinth line, over plinth and below-DPC insulation boards, where the build-up needs a hard-wearing face at splash height.
Why a Resin-Bound Quartz Finish Works at Ground Level
The construction is the argument: transparent resin binders holding coloured quartz grits, rather than a pigmented film sitting on a mineral coat. Four declared properties follow from that, and each one earns its place at the bottom of a wall.
- Impact resistance, category I under ETAG 004 — the classification specified where a surface is within reach, which is exactly the plinth and entrance zone.
- Water absorption category W3, w ≤ 0.1 kg/m²·h⁰·⁵ under EN 15824, the lowest-absorption band in that standard, so splashback and driven rain stay on the surface.
- Vapour permeability category V2 under EN 15824, meaning moisture in the wall keeps a route outward through the finish.
- Easy to keep clean and resistant to scrubbing, in the sheet's own terms — a practical advantage where road spray reaches the wall, and the guide to algae growth on render covers what to do when a shaded elevation colours up.
CT 177 Technical Data — Declared Values and the Scope of Each
| Property | Declared value |
|---|---|
| Grain size | 1.0–1.6 mm coloured quartz grits |
| Base | Aqueous synthetic resin dispersion with coloured mineral fillers |
| Density | approx. 1.75 kg/dm³ |
| Adhesion | 0.6 MPa, EN 15824 |
| Interlayer adhesion after ageing | ≥ 0.08 MPa, ETAG 004 |
| Water absorption | Category W3, w ≤ 0.1 kg/m²·h⁰·⁵, EN 15824 |
| Water absorption after 24 hours | < 0.5 kg/m², ETAG 004 |
| Water vapour permeability | Category V2, 0.14 ≤ Sd < 1.4 m, EN 15824 |
| Water vapour, ETAG test | Sd ≤ 1.0 m, ETAG 004 |
| Thermal conductivity | λ = 0.61 W/(m·K), EN 15824 |
| Impact resistance | Category I, ETAG 004 |
| Application temperature | +10 °C to +25 °C, air and substrate |
| Relative humidity during work | below 80% |
| Preliminary drying time | approx. 30 minutes |
| Rain resistance | after approx. 3 days |
| Maximum water addition | 250 ml per 25 kg |
| Shelf life | 12 months from production, protect from frost |
| Declaration of Performance | No. 00469, EN 15824 |
Two of those rows repay a second look. The vapour figure appears twice — a V2 class under EN 15824, which is the product's own classification, and a separate Sd ≤ 1.0 m from the ETAG 004 test regime; quote the EN 15824 line when a specifier asks what the render is classified as. The λ of 0.61 W/(m·K) is the conductivity of a decorative layer a couple of millimetres thick, so it belongs in a build-up calculation and never stands as a wall U-value on its own.
All declared values assume a substrate, ambient and material temperature of +23 °C at 50% relative humidity. A cool, damp UK morning slows every timing on that list, which is worth building into the day rather than discovering at four o'clock.
How to Mix and Apply CT 177 — Water Cap, Layer Thickness and Wet-on-Wet Working
- Stir the bucket before use with a slow-speed drill and basket mixer to a homogeneous consistency. Over-mixing is a real fault here: the sheet warns that prolonged, intensive stirring discolours the aggregate and aerates the mass.
- Add water only if needed, and cap it at 250 ml per 25 kg. Beyond that the sheet states the material becomes unusable, so measure it rather than pouring by eye.
- Lay it on with a stainless steel trowel at a minimum of 1.5 times the grain thickness, evenly across the panel.
- Work wet-on-wet and smooth out, keeping one plane going without processing breaks and holding the same consistency throughout.
- Tape any unavoidable break. Run self-adhesive tape along a defined line, apply, smooth, then pull the tape with the fresh material still on it and restart from that edge.
Two prohibitions sit alongside those steps and both are explicit: do not sprinkle the plaster with water, and do not rub the surface back once it is smoothed. Trade practice adds one more — keep the trowel passes running in a single direction, because a circular action rearranges 1.0–1.6 mm grits into swirls that low sun will find later.
On quantities, this page publishes no coverage rate and no bucket count. That is an editorial hold placed on the record rather than a gap in the document, and the reasoning is explained in the ordering section below. The mosaic plinth application guide walks the same sequence in site order, including how the priming stage is set up.
Substrates, the Priming Sequence and Curing Conditions
Every declared substrate reaches CT 177 through a quartz primer, and the sheet is specific about which one and after how long. Ceresit CT 16 is the named quartz primer, stocked here in the exterior render primers range, and the sheet recommends tinting it close to the mosaic colour so nothing shows through the transparent binder.
| Substrate | Age or condition | Priming |
|---|---|---|
| Cement and cement-lime plaster | over 28 days | CT 16 quartz primer |
| Concrete | over 3 months, moisture ≤ 4% | CT 16 quartz primer |
| Mesh-reinforced layers in ZU, CT 85, CT 190 or CT 100 | over 3 days | CT 16 quartz primer |
| CT 87 mortar | over 2 days | CT 16 quartz primer |
| Absorbent substrates | — | CT 17, then CT 16 after minimum 2 hours |
| Gypsum, boards and sound paint | indoors only | CT 17, then CT 16 |
The render goes on only once the CT 16 has dried completely, and the substrate itself must be even, load-bearing, dry, colour-uniform and free of grease, bitumen and dust. Cavities and unevenness are filled beforehand — CT 29 putty is the sheet's suggestion — so the finished plane is set by the preparation rather than by the decorative coat.
Through the cure, protect the work with netting or tarpaulins until it has fully hardened, and avoid applying to walls in strong sunlight. A milky cast on fresh material is normal and clears as it dries; prolonged water contact can bring it back temporarily until the surface dries again, so three rain-free days after application is the condition to plan for.
Reading the Fire Class Correctly — It Belongs to the System, Not the Bucket
The sheet's reaction-to-fire lines are stated per Ceresit Ceretherm system, and they are not a property of the render on its own. Quote them with the system named, or not at all.
| Ceretherm system | Reaction to fire, EN 13501-1 | ETA |
|---|---|---|
| Visage | B-s1,d0 | 11/0395 |
| Popular | B-s2,d0 | 08/0309 |
| Classic | B-s2,d0 | 09/0014 |
| Premium | B-s2,d0 | 08/0308 |
| Wool Classic | no class stated on this sheet | 09/0026 |
Three of the four classified systems sit at B-s2,d0, and only Visage is listed at B-s1,d0 — so a specification written against B-s2,d0 holds across the wider set. Wool Classic carries an ETA on the same sheet with no fire line beside it, and Ceretherm Reno appears under a Polish national assessment, ITB-KOT-2018/0472, likewise without one; neither gap is filled by borrowing a neighbouring system's class. For UK work, reaction to fire is assessed for the wall as built under current Approved Document B guidance, and the render's contribution is one input to that.
Colour Choice and the Light Reflectance Condition
The sheet attaches a condition to colour that most mosaic listings leave out, and it explains why this material is a plinth product rather than a whole-elevation one. Ceresit recommends a light reflectance coefficient of HBW 20 or above, and directs anyone specifying below that to consult its technical department so the insulation system can be selected to suit.
With intense dark colours, the sheet limits CT 177 as a facade layer within a Ceretherm system to small areas such as plinths and architectural details. Deep shades on large surfaces are a heat question rather than a colour-fastness one, which the guide to dark colours and solar heat on render sets out, and the decorative facade guidance covers pairing a mosaic plinth with a lighter finish above it.
Choosing Between the 25 kg and 10 kg Buckets
Both packs are the same product under the same data sheet and the same Declaration of Performance, so the choice is about how much wall is in front of you and how many part-used buckets you want left over.
| Pack | Practical difference | Suits |
|---|---|---|
| 25 kg bucket | Fewer batch codes across one plane | Continuous plinth runs, full elevations |
| 10 kg bucket | Smaller commitment per colour | Reveals, returns, patch repairs |
One instruction governs both, and it is the sheet's own: use material from the same production batch number on a single plane. That is the practical case for the larger pack wherever an uninterrupted surface is involved.
Ordering the 25 kg Bucket — Price, Stock and Batch Continuity
The Ceresit CT177 mosaic render 25kg bucket is listed at £79.00 as displayed in August 2026, and the live record currently shows it as out of stock. VAT treatment is not shown in that record, so this page states nothing about it; the 10 kg pack and the collection page carry their own live availability.
No price per square metre appears here, and that is deliberate. The record carries a standing instruction from Renders World not to publish a coverage figure for CT 177 until the operator lifts it, on the reasoning that yield on a mosaic render moves with grain and substrate. Without a published coverage rate there is no honest divisor, so the bucket price stands on its own and the quantity comes off the printed pack or your own measured trial area.
- Confirm the colour reference and batch when ordering, and buy a single plane's worth together.
- Order the CT 16 primer at the same time, tinted towards the aggregate shade — it is a required layer, not an optional extra.
- Check the working window against +10 °C to +25 °C and three protected days before booking the scaffold.
FAQ — CT 177 Compatibility, Limits and Storage
Which primer goes under CT 177, and is it optional?
Ceresit CT 16 quartz primer is named for every declared substrate and is not optional. On absorbent substrates the sequence starts with CT 17, then CT 16 after a minimum of two hours, and on interior gypsum or board substrates the same two-stage sequence applies. Tinting the CT 16 close to the aggregate colour keeps the base coat from reading through the transparent binder.
How do I work out how much to order?
Take the yield printed on the bucket, apply it to your measured area, and add for corners and reveals. This page holds back a published coverage rate under a standing instruction on the record, so the pack itself and your supplier's confirmation are the figures to plan against. For a repeat colour, ordering a single batch for each continuous plane matters as much as the total quantity.
What are the limits for cold or damp conditions?
Air and substrate both need to sit between +10 °C and +25 °C with relative humidity under 80%, and the surface wants roughly three days of protection before it is rain resistant. Sheeted scaffolding widens the usable season, and the declared timings assume +23 °C at 50% humidity, so allow longer whenever conditions fall short of that.
Can it be used in permanently damp locations?
The sheet advises against areas exposed to long-lasting moisture and notes that moisture pressure from behind can damage the rendering, so appropriate sealing layers need to be in place first. On a plinth, that means the below-DPC detailing and drainage are resolved before the decorative layer goes on, which is where this material performs at its best.
How should buckets be stored?
Up to 12 months from production in cool conditions and the original undamaged packaging, protected from frost. High temperatures and direct sunlight matter just as much, since the sheet warns that storing or transporting the material hot can start the setting process; reseal any opened bucket tightly and use it up promptly.
Technical Documentation — Ceresit CT 177