Description
Tinted on a dedicated Ceresit mixing 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 combines silicate mineral hardness with silicone flexibility in a single 25 kg tub, covering approximately 10 m² at 2.5 kg/m² with a dense stone-textured finish certified V1/W3 under EN 15824:2017. Part of the premium silicone render range, this dual-binder formula achieves the highest vapour permeability class in the Renders World silicone line-up, making it the specification of choice for mineral-wool-backed ETICS systems, solid-wall retrofit insulation, and any UK elevation where moisture must escape freely outward through the facade.
The hybrid chemistry sits between pure silicone and pure silicate finishes. Silicone delivers elasticity and hydrophobic self-cleaning behaviour, while the silicate component bonds tightly to mineral substrates and accelerates the surface set. Through-body pigmentation runs colour throughout the render mass, so minor surface scuffs never expose a different shade underneath — a meaningful advantage over painted finishes on traffic-prone elevations and lower facade zones. The integrated BioProtect formula provides active resistance to algae, mould, and fungi across the UK's damp climate zones, with measurable benefit on shaded north-facing walls.
Why Trade Specifiers Choose CT174 1.5 mm
- Highest Vapour Permeability in the Silicone Range: V1-rated breathability under EN 15824 lets interior moisture pass freely outward through the render layer, keeping wall structures dry and mineral wool insulation performing at its designed lambda — the single most important specification driver on solid-wall retrofits and timber-frame buildups.
- Crack-Resistant Hybrid Flexibility: The silicone component gives the finish an elastic polymer matrix that moves with seasonal thermal expansion, absorbing freeze-thaw cycles and rapid UK temperature swings without micro-cracking — the hybrid formula tolerates substrate movement that a pure silicate render alone cannot manage.
- Self-Cleaning Hydrophobic Surface: Low surface tension means rainwater sheets across the finish rather than pooling in the texture, flushing away urban dust, pollen, and atmospheric pollutants — reducing manual facade cleaning intervals across the building's life, with the dark colours and solar heat risk guide covering surface-temperature limits for very dark shades on south-facing walls.
- Built-In Biological Defence: BioProtect embeds active biocidal agents in the render mass, inhibiting algae, mould, and fungal colonisation for the lifetime of the coat — keeping shaded north-elevation facades visually clean where unprotected surfaces typically show green algae 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 Ceresit machine at our Southampton warehouse, with bespoke RAL, NCS, and competitor-shade matching mixed to order on the same equipment — every tub arrives ready to apply with next-day UK dispatch.
- Versatile Hand or Machine Application: Suitable for trowelling and machine spraying, so professional renderers can match method to project scale — from a single domestic elevation through to multi-block housing schemes, with consistent stone texture across both routes.
- System Component for Ceretherm ETICS: Integrates as a certified decorative finish layer within Ceresit Ceretherm assemblies, giving specifiers a single-source build-up from insulation board through basecoat, primer, and 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 (lifetime of coat) |
| Colour Range | Full Ceresit Colours of Nature plus bespoke RAL/NCS matching |
| Mandatory Primer | Ceresit CT 16 quartz primer (24 h cure before render) |
| Standard Compliance | EN 15824:2017 · DoP 145/3/CPR · Ceretherm BBA-certified 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 that has been primed with Ceresit CT 16 quartz primer at least 24 hours before rendering. The render integrates directly into Ceresit Ceretherm ETICS assemblies and pairs with the broader Renders World system range for a single-source specification from insulation board through to decorative finish. 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 layer to create the stable, crack-resistant substrate this render is designed to bond with.
- Compatible Insulation Types: Graphite EPS boards, standard white EPS, mineral wool slabs, and XPS boards within ETICS assemblies — suitable for new-build facades, solid-wall retrofit insulation, and over-cladding projects across UK climate zones.
- Substrate Versatility: Performs best on reinforced basecoats over masonry, concrete, and existing well-bonded mineral renders, provided the surface is clean, dry, structurally sound, and primed with CT 16.
- Mandatory Priming Step: CT 16 quartz primer regulates suction and creates an evenly keyed surface so CT174 bonds uniformly across the entire elevation — a properly primed wall delivers a consistent, blemish-free finish from edge to edge.
- Weather Window: Schedule application when air and substrate temperatures sit between +5 °C and +25 °C with humidity below 80%, and protect from direct sun, driving rain, and wind for at least 24 hours after texturing.
For the full step-by-step method covering tools, hawk technique, joining wet edges, and finishing sequence, the thin-coat render application step-by-step guide covers the complete process for UK walls, and the seasonal application timing guide covers weather-management protocols throughout the UK calendar year.
Installation Notes — Mixing, Texturing, and Drying
Preparing the surface properly before you start is the single most valuable step for a flawless CT174 1.5 mm finish. Ensure the primed basecoat is fully cured (minimum 24 hours after CT 16 application), then stir the tub contents with a low-speed mechanical mixer until the consistency is uniform before loading a hawk or machine hopper. For the cleanest joins, work each elevation in a continuous wet-on-wet pass rather than stopping mid-wall — this maintains a seamless stone texture across the full surface and eliminates visible lap marks.
- Trowel Technique: Apply at the thickness of the 1.5 mm grain using a stainless-steel float held at a slight angle, then texture immediately with a plastic float in circular motions to produce the characteristic densely packed aggregate finish.
- Open Time Awareness: CT174 has a noticeably shorter open time than pure silicone renders — approximately 15–20 minutes before the silicate binder starts to firm — so work in sections no wider than arm's reach and texture immediately rather than floating a full bay first.
- Drying Schedule: Surface dry in 24 hours under typical UK conditions; full cure in 48–72 hours. Protect the freshly rendered facade from rain, frost, and direct strong sun for the first 24 hours after texturing.
- Sequence Within the Bay: On taller elevations, two renderers working in tandem keeps the wet edge alive right across the wall — the most reliable way to produce a uniform stone finish with zero lap marks on facades wider than 4 metres.
Pro Tips From UK Installers Using CT174 1.5 mm
The single biggest difference experienced renderers flag with CT174 versus a pure silicone is the open time — the silicate binder component sets the pace, so the working window shortens noticeably. These site-tested habits keep the finish uniform on real UK projects:
- Texture inside the 15-minute window: The silicate binder firms faster than pure silicone, so floating a bay then coming back to texture rarely works. Apply and texture in the same continuous motion across each arm-width section.
- Run two renderers on bays wider than 4 metres: Keeping the wet edge alive across a long elevation is the single most reliable predictor of a uniform stone finish without lap marks.
- Give CT 16 a full 24 hours to cure: A properly cured primer pulls the render onto the wall evenly — the 1.5 mm grain practically floats into texture with minimal trowel pressure once the substrate suction is correctly regulated.
- Budget at 2.5 kg/m² and order 5–10% extra: Use the render coverage calculator to build the full materials list before ordering — the single step that protects an entire materials budget from a mid-project shortfall.
- Plan ETICS layer cure times into the programme: Adhesive cure (3 days), basecoat plus mesh cure (3 days), primer cure (24 hours), then render — adding the full week into the programme up front avoids the temptation to compress curing windows under weather pressure.
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 choice when your project needs V1 vapour permeability and W3 water resistance on a mineral-wool or EPS system — ideal for solid-wall retrofits, new-build insulated facades, and any elevation where moisture management and long-term self-cleaning performance are the priority.
- Need a finer grain for machine-only application on commercial scale? The CT174 machine-applied 1.0 mm variant in the same silicate-silicone range delivers identical hybrid-binder performance with a smoother, finer stone texture and lower coverage of approximately 1.8–2.1 kg/m², optimised for professional spray rigs on commercial elevations above 100 m².
- Looking for a longer working window on complex detailing? The broader premium silicone render range includes pure silicone finishes with extended open times of 30+ minutes — a practical advantage for solo renderers, intricate window-reveal detailing, and projects where extra working time materially affects the finish quality.
FAQ — CT174 Coverage, Compatibility, Ordering
How many tubs of CT174 1.5 mm do I need for my project?
Each 25 kg tub covers approximately 10 m² at the standard application rate of 2.5 kg/m², so a 100 m² facade typically requires 10–11 tubs. Adding 5–10% for detailing around window reveals, corners, and site waste ensures enough material to complete the job without interruption.
Which primer does CT174 require, and can I use a different brand?
Ceresit CT 16 quartz primer is the mandatory specification for CT174 within the Ceretherm certified system — the quartz aggregate creates the keyed, suction-regulated surface that the silicate-silicone binder needs to bond uniformly. Using an alternative primer falls outside the Ceretherm BBA certification scope, so for warranty-backed projects keep to CT 16 and allow a full 24-hour cure before rendering.
Can I use dark colours on south-facing walls with CT174?
Mid-range and lighter shades perform confidently on any orientation thanks to the flexible silicone component, which accommodates thermal cycling across the day. For very dark colours with a low Heat Brightness Value (below HBW 25) on south- or west-facing elevations, Ceresit CT 76 Solar Protect is specifically formulated with heat-reflective pigments to manage higher surface temperatures — your installer or specifier can confirm the HBW rating of your chosen shade to determine whether CT174 or CT 76 is the best match for that elevation.
What colours are available and can you match a shade from another manufacturer?
CT174 is supplied across the full Ceresit Colours of Nature palette, tinted on a dedicated Ceresit machine at our Southampton warehouse and ready for next-day dispatch. For projects requiring a shade outside the standard Ceresit range — a specific RAL code, an NCS reference, or a colour matched from another manufacturer's swatch — our team mixes bespoke colours to order on the same equipment. Our warehouse also mixes the Atlas 480-shade SAH palette on a separate dedicated machine, bringing the combined colour choice across both systems to over 1,000 standard shades plus bespoke matching. Browse the colour sample catalogues to view both palettes on physical rendered swatches.
Does CT174 need painting after application?
CT174 is a through-coloured render, meaning the pigment is distributed throughout the entire mass rather than applied as a surface coating. The built-in colour does not peel, flake, or require repainting, so the facade remains maintenance-light for the full service life of the finish. The self-cleaning surface ensures atmospheric dust is washed away naturally by rainfall, keeping the appearance fresh without manual intervention.
Is CT174 an environmentally responsible specification?
CT174 is a water-based formulation with very low volatile organic compound (VOC) content, producing minimal fumes during application and curing — safer for installers working on enclosed scaffold. The thin 1.5 mm application rate uses approximately 2.5 kg/m², a fraction of the 30–40 kg/m² that traditional sand-and-cement renders require at 15–20 mm thickness, significantly reducing material consumption and site waste per square metre. Through-body colour eliminates the recurring resource cycle of periodic repainting, and Ceresit's Eco Bucket packaging uses up to 62% post-consumer recycled polypropylene.
Technical Documentation — CT174 1.5 mm TDS and DoP