Description
Ceresit CT16 is the quartz key coat that goes on after the background is sound and before the finish is laid. Renders World stocks it in the 10 l container, and it belongs to a narrow job: making a smooth, even, low-suction surface grip a thin-coat finish. The rest of the range that goes on before a finish covers the consolidating products that do the other half of the work.
What Ceresit CT16 Does to a Background
It is a dispersion of synthetic resins carrying fine aggregate, and the manufacturer credits it with three separate effects rather than one. They matter in different situations, which is why the product is worth understanding before it is ordered.
- Suction drops sharply. Priming considerably decreases the background's absorption, which stops the products laid over it from drying too fast — the usual reason a thin-coat finish goes patchy across one elevation.
- The surface gains a mechanical key. The fine aggregates make the primed face rough and scratch resistant, and the expanded area increases the adhesion of renders, putties and paints.
- Colour evens out. Ceresit CT16 has strong coating properties that make the background efficiently homogenous, preventing stains forming on coloured acrylic, mineral, silicate-silicone, silicone and elastomeric finishes.
That third effect names finish chemistries by type, which is a wider compatibility statement than any single system approval gives, and it is why the primer matters most under pale and strongly coloured work. The headline properties are short: waterproof, vapour permeable, high opacity, ready to use, applied by roller or brush.
The Figures, and Which Unit They Come In
| Property | Value |
|---|---|
| Base | Synthetic resin dispersion, mineral fillers |
| Density | Approx. 1.5 kg/dm³ |
| Consumption | 0.2–0.35 l/m², or 0.3–0.5 kg/m² |
| Consumption varies with | Smoothness and absorption of the background |
| Application temperature | +5 °C to +25 °C, air and background |
| Humidity | Below 80% |
| Drying time | Approx. 3 hours |
| Dilution | Do not dilute |
| Method | One even layer, roller or brush |
| Shelf life | 12 months from production, stored cool |
| Storage | Protect from frost and direct sunlight |
| Packaging quoted by Ceresit | Plastic buckets, 5 kg and 15 kg |
The consumption row needs care. It comes in two units for the same material, and they are alternatives rather than one wide band: 0.2–0.35 l/m² by volume, 0.3–0.5 kg/m² by weight. Quoting the litre floor against the kilogram ceiling produces a range about 40% too generous at the top.
Coverage in Containers, Not per Square Metre
Ceresit publishes consumption per square metre and no coverage per container, so the figure a buyer actually needs has to be worked out. Doing it once, in the open:
- By volume: 10 l ÷ 0.2 l/m² = 50 m² on a smooth, tight background; 10 l ÷ 0.35 l/m² = about 29 m² on an open, absorbent one.
- By weight: 15 kg ÷ 0.3 kg/m² = 50 m²; 15 kg ÷ 0.5 kg/m² = 30 m². The two methods agree, which is the check that pack size and density are consistent.
- On a 100 m² elevation: 20 to 35 litres, so three containers for a typical background and four where the surface is open-textured.
There is a packaging point behind that arithmetic. Ceresit lists 5 kg and 15 kg buckets and no 10 l one. At approximately 1.5 kg/dm³, 10 l weighs about 15 kg, so the container Renders World sells is the 15 kg bucket described by volume rather than by weight.
The Ceretherm Assessments, With Their Numbers
Ceresit CT16 carries a European Technical Assessment inside named Ceretherm systems, and each assessment has its own certificate and Declaration of Performance number. A specification that asks for one usually needs all three, so they sit together:
| Ceretherm system | ETA | Certificate | DoP |
|---|---|---|---|
| Popular | 08/0309 | 1488-CPR-0382/Z | 00426 |
| Classic | 09/0014 | 1488-CPR-0439/Z | 00420 |
| Visage | 11/0395 | 1488-CPR-0370/Z | 00431 |
| Wool Classic | 09/0026 | 1488-CPR-0440/Z | 00424 |
| Universal EPS | 13/0535 | 1488-CPR-0457/Z | 00433 |
| Universal XPS | 13/0807 | 1488-CPR-0456/Z | 00434 |
| Universal MW | 14/0127 | 1488-CPR-0362/Z | 00435 |
Alongside those, Ceresit records national Technical Assessments for Ceretherm Popular (15-6894/2013, certificate ITB-0068/Z, DoC 00442), Classic (15-4397/2013, ITB-0109/Z, DoC 00440), Reno (15-8077/2009, ITB-0701/Z, DoC 00444) and Wool Garage (15-7956/2016, ITB-0320/Z, DoC 00448), each with annexes.
Ceresit CT16 is also recorded as possessing BBA Certificate No. 14/5142 and Irish Agrément Board Certificate No. 09/0340. An assessment belongs to the assembly it was granted for, so a specification is answered by quoting the system beside the number rather than the number alone. The BBA reference is published without a scope or a date, and that boundary is worth knowing before the number goes into a submission.
Getting the Background Right First
What goes underneath is specified tightly: smooth, even, dry, and free of grease, bitumen, dust and anything else that reduces adhesion. Dirt and weak coats come off. Existing adhesive and lime paint coatings come off. Beyond that, the order of operations decides the result, and it runs as follows.
- Absorbent backgrounds take a penetrating primer first. Gypsum renders, chipboards and non-impregnated plasterboard are primed with Ceresit CT 17 and left about two hours before the key coat follows.
- Suitable backgrounds: chipboards, plasterboard, gypsum renders, all types of concrete and strong paint coats, inside and outside buildings.
- Defects come before priming. Gaps in the render are filled with Ceresit CT 29 and impurities washed off with a CT 98 agent — neither is stocked at Renders World, and both are named here because the document names them.
What changes between brick, block and previously painted walls is covered in the preparation sequence guide and the background-by-background matrix.
Applying It: One Layer, No Shortcuts
Stir the container before use, and keep rusty containers and rusty tools away from it — iron contamination stains a pale finish months after the scaffold comes down. Apply one even layer by roller or brush, allow approximately three hours, and wash tools and fresh splashes with water before they cure. The working window is +5 °C to +25 °C for air and background alike, humidity under 80%.
- Do not dilute. The instruction is unqualified, and thinning cuts the aggregate density that produces the key in the first place.
- Match the colour to the finish. Under a thin-layer render, Ceresit CT16 is specified in the colour corresponding to that of the render.
- Allow for the weather. Published values were taken at +23 °C and 50% relative humidity, and hardening runs faster or slower in other conditions, so judge the surface rather than the clock.
- Eyes: on contact, rinse with water and consult a general practitioner.
The full site method, including how the primed elevation is handed over to the render trade, is set out in the application guide for EWI systems.
Where Ceresit CT16 Sits Among the Primers
Products on this shelf get confused with one another, and the difference is what each one is for:
- A key coat — Ceresit CT16 — leaves a rough, aggregate-bearing surface for a thin-coat finish to grip.
- A penetrating primer — CT 17 — soaks into and binds a weak or dusty background, and its own documentation sends thin-layer work to a key coat rather than to itself.
- A white trade bucket — Cerplast quartz top coat primer — is the key coat stocked here in a 25 kg pack.
On an absorbent background both a penetrating primer and a key coat are needed, in that order, not one instead of the other. Which way a particular job falls is worked through in the comparison of primer types. Below the DPC, Ceresit CT16 is the mandated substrate coat under Ceresit CT 177 mosaic, where the build-up steps down to the plinth.
Questions Buyers Ask
How many containers does a 100 m² elevation take?
The arithmetic decides it:
- At 0.2 l/m², a smooth background takes 20 litres — two containers, with little margin.
- At 0.35 l/m², an open one takes 35 litres, which rounds up to four.
- A test area on the actual wall beats any average, because consumption follows the surface rather than the specification.
Can it be thinned to go further?
No. The instruction is to not dilute, without qualification. The aggregate content is what produces the rough, scratch-resistant surface the finish keys into, so thinning works directly against the reason for buying it.
Does it replace a penetrating primer?
It does not. Absorptive backgrounds go to the deep-acting primer first with about two hours of drying, and Ceresit CT16 follows over the top. The two sit in different consumption bands and do different work.
Is Quarz Contact the same product?
Yes. Quarz Contact is Ceresit's trade name for this priming paint and appears on the manufacturer's own product listing. The technical documentation titles it simply CT 16 Priming Paint, so a specification may carry either wording.
Technical Documentation