Description
Tinted on a dedicated Ceresit machine at our Southampton warehouse and dispatched next day across the UK, Ceresit CT174 hybrid silicate-silicone render in 1.5 mm grain delivers V1 vapour permeability with W3 water resistance, the highest combined breathability rating in the Renders World silicone range, certified to EN 15824:2017 under DoP 145/3/CPR.
Where CT174 1.5 mm Silicate-Silicone Render Performs Best — UK Walls and Substrates
Ceresit CT174 1.5 mm silicate-silicone render is a hybrid thin-coat facade plaster that pairs silicate mineral hardness with silicone flexibility in one 25 kg tub, covering roughly 10 m² at 2.5 kg/m² with a dense stone-textured finish certified V1/W3 under EN 15824:2017. It sits in the premium silicone render range as the highest vapour-permeability finish in the line-up, which is exactly why specifiers reach for it on the projects where moisture management decides everything.
The dual-binder chemistry sits between a pure silicone and a pure silicate finish. The silicone fraction brings elasticity and a hydrophobic, self-cleaning surface; the silicate fraction bonds tightly to mineral substrates and firms the surface faster. Through-body pigmentation carries colour throughout the render mass, so a minor surface scuff never exposes a different shade underneath, which matters on lower facade zones and traffic-prone elevations.
The integrated BioProtect formula adds active resistance to algae, mould, and fungi, with the clearest benefit on shaded north-facing walls across the UK's damp climate zones. Renders World stocks the full system around it, so a specifier can build the whole assembly from one source and know the finish, primer, and mesh have been tested to work together.
Why Trade Specifiers Choose CT174 1.5 mm
- Highest vapour permeability in the silicone range: the V1 breathability class under EN 15824 lets interior moisture pass freely outward through the render, keeping wall structures dry and mineral wool insulation performing at its designed lambda, the single biggest specification driver on solid-wall retrofits.
- Crack-resistant hybrid flexibility: the silicone component forms an elastic polymer matrix that moves with seasonal thermal expansion and freeze-thaw cycling, tolerating substrate movement that a pure silicate render alone cannot manage.
- Self-cleaning hydrophobic surface: low surface tension means rainwater sheets across the finish and flushes away urban dust and pollutants, so facade cleaning intervals stretch out across the building's life.
- Built-in biological defence: BioProtect embeds biocidal agents in the render mass to inhibit algae and mould for the life of the coat, keeping shaded elevations clean where unprotected surfaces typically green within three to four UK winters.
- Over 1,000 colours mixed on site: the full Ceresit Colours of Nature palette is tinted on a dedicated machine at the Renders World Southampton warehouse, with bespoke RAL, NCS, and competitor-shade matching mixed to order and dispatched next day.
- Hand or machine application: suitable for trowelling and machine spraying, so renderers match method to project scale and keep a consistent stone texture across both routes.
- Certified Ceretherm system component: integrates as a decorative finish layer within Ceresit Ceretherm ETICS assemblies, giving a single-source build-up from board through to finish.
Technical Specifications — CT174 1.5 mm Data Sheet Highlights
| Property | Value |
|---|---|
| Pack size | 25 kg |
| Binder type | Silicate-silicone hybrid (potassium water glass + silicone resin) |
| Grain size | 1.5 mm — densely packed stone texture |
| Density | Approx. 1.7 kg/dm³ |
| Coverage rate | Approx. 2.5 kg/m² — approx. 10 m² per 25 kg tub |
| Vapour permeability class | V1 (high) — EN 15824 |
| Water absorption class | W3 (low) — EN 15824 |
| Adhesion to substrate | ≥ 0.35 MPa |
| Application temperature | +5 °C to +25 °C (air and substrate) |
| Open time | Approx. 15–20 minutes before texturing |
| Biological protection | BioProtect — algae, mould, fungi |
| Mandatory primer | Ceresit CT 16 quartz primer (24 h cure before render) |
| Standard compliance | EN 15824:2017 · DoP 145/3/CPR · Ceretherm system component |
How to Apply CT174 1.5 mm — Substrates, Priming, and Open Time
CT174 1.5 mm is designed to bond to a reinforced thin-coat basecoat primed with Ceresit CT 16 quartz primer at least 24 hours before rendering. Prime the cured basecoat with a quartz primer from the exterior render primers range, specifically CT 16 to match the certified Ceretherm system, and embed 150 g/m² fibreglass mesh in the basecoat to create the stable, crack-resistant substrate this render is built to bond with.
- Compatible insulation: graphite EPS, standard white EPS, mineral wool, and XPS within ETICS assemblies — suitable for new-build facades, solid-wall retrofit, and over-cladding across UK climate zones.
- Substrate versatility: performs best on reinforced basecoats over masonry, concrete, and well-bonded mineral renders, provided the surface is clean, dry, sound, and primed with CT 16.
- Mandatory priming: CT 16 regulates suction and keys the surface so CT174 bonds uniformly, delivering a consistent finish from edge to edge.
- Weather window: apply when air and substrate sit between +5 °C and +25 °C with humidity below 80%, and protect from sun, driving rain, and wind for at least 24 hours after texturing.
For the complete method covering tools, hawk technique, and joining wet edges, the thin-coat render application step-by-step guide walks through the full process for UK walls, and the seasonal timing guide on when to apply silicone render in the UK covers weather management across the calendar year.
Installation Notes — Mixing, Texturing, and Drying
Getting the surface right before you start is the most valuable step toward a flawless CT174 finish. With the primed basecoat fully cured, stir the tub with a low-speed mechanical mixer until uniform, then load a hawk or machine hopper. For the cleanest joins, work each elevation in a continuous wet-on-wet pass rather than stopping mid-wall, which holds a seamless stone texture across the full surface.
- Trowel technique: apply at the thickness of the 1.5 mm grain with a stainless-steel float held at a slight angle, then texture immediately with a plastic float in circular motions for the dense aggregate finish.
- Open-time awareness: the silicate binder firms faster than pure silicone, so work in sections no wider than arm's reach and texture as you go rather than floating a full bay first.
- Drying schedule: surface dry in around 24 hours under typical UK conditions, full cure in 48–72 hours; protect from rain, frost, and strong sun for the first 24 hours.
- Bay sequence: on taller elevations, two renderers working in tandem keep the wet edge alive across the wall, the most reliable route to a uniform finish without lap marks on facades wider than 4 metres.
Pro Tips From UK Installers Using CT174 1.5 mm
The habit experienced renderers flag first with CT174 is the open time: the silicate binder sets the pace, so the working window is shorter than a pure silicone. These site-tested habits keep the finish uniform on real UK projects.
- Texture inside the 15-minute window: the silicate binder firms fast, so applying and texturing in one continuous motion across each arm-width section beats floating then returning.
- Run two renderers on bays over 4 metres: keeping the wet edge alive across a long elevation is the strongest predictor of a uniform stone finish.
- Give CT 16 a full 24 hours to cure: a properly cured primer pulls the render on evenly, and the 1.5 mm grain floats into texture with light trowel pressure once suction is regulated.
- Budget at 2.5 kg/m² and order 5–10% extra: build the full materials list first with the render coverage calculator, the single step that protects a materials budget from a mid-project shortfall.
- Plan ETICS cure times into the programme: adhesive (3 days), basecoat and mesh (3 days), primer (24 hours), then render — adding the full week up front avoids compressing curing windows under weather pressure.
How CT174 1.5 mm Compares to the Machine 1.0 mm Variant
Both renders share the same silicate-silicone hybrid chemistry and V-class breathability; the decision between them comes down to grain, application method, and project scale. The table below shows where each one fits.
| Variant | Key Spec | When to Choose |
|---|---|---|
| CT174 1.5 mm | 2.5 kg/m² · hand or machine · V1 | Domestic to multi-block, hand-applied detail |
| CT174 Machine 1.0 mm | ~1.8–2.1 kg/m² · machine only · finer texture | Large commercial spray jobs above 100 m² |
Is CT174 1.5 mm Silicate-Silicone Render Right for Your Project?
- Yes — for breathable, crack-resistant ETICS facades: CT174 1.5 mm is the right call when the project needs V1 vapour permeability and W3 water resistance on a mineral-wool or EPS system — solid-wall retrofits, new-build insulated facades, and any elevation where moisture management and self-cleaning are the priority.
- Need a finer, machine-only texture at scale? The CT174 machine-applied 1.0 mm variant delivers identical hybrid-binder performance with a smoother finish and lower coverage, optimised for spray rigs on commercial elevations.
- Want a longer working window on intricate detailing? The wider premium silicone render range includes pure silicone finishes with extended open times, a practical advantage for solo renderers and complex window-reveal work.
FAQ — CT174 Coverage, Compatibility, Ordering
How many tubs of CT174 1.5 mm do I need?
Each 25 kg tub covers approximately 10 m² at the standard rate of 2.5 kg/m², so a 100 m² facade typically needs 10–11 tubs. Adding 5–10% for detailing around reveals, corners, and site waste ensures enough material to finish without interruption.
Which primer does CT174 require, and can I substitute a brand?
Ceresit CT 16 quartz primer is the specification for CT174 within the Ceretherm system, since the quartz aggregate creates the keyed, suction-regulated surface the binder needs to bond uniformly. An alternative primer falls outside the Ceretherm certification scope, so for warranty-backed projects keep to CT 16 and allow a full 24-hour cure.
Can I use dark colours on south-facing walls?
Mid-range and lighter shades perform confidently on any orientation thanks to the flexible silicone component. For very dark colours on south- or west-facing elevations, a heat-reflective formulation such as Ceresit CT 76 Solar Protect manages higher surface temperatures, and your specifier can confirm the brightness value of a chosen shade to decide which finish suits that elevation best.
What colours are available, and can you match another manufacturer's shade?
CT174 is supplied across the full Ceresit Colours of Nature palette, tinted on a dedicated machine at the Renders World Southampton warehouse for next-day dispatch. For a specific RAL code, NCS reference, or a colour matched from another swatch, the team mixes bespoke shades to order. Browse the colour sample catalogues to view the palette on physical rendered swatches.
Does CT174 need painting after application?
CT174 is through-coloured, so pigment runs throughout the render mass rather than sitting as a surface coating. The colour does not peel, flake, or need repainting, and the self-cleaning surface lets rainfall wash atmospheric dust away, keeping the facade maintenance-light for the service life of the finish.
Is CT174 an environmentally responsible specification?
CT174 is water-based with very low VOC content, producing minimal fumes during application and curing. The thin 1.5 mm rate uses roughly 2.5 kg/m², a fraction of the 30–40 kg/m² a traditional sand-and-cement render needs at 15–20 mm, cutting material consumption and site waste per square metre. Through-body colour also removes the recurring resource cycle of repainting.
Technical Documentation — CT174 1.5 mm TDS and DoP