Description
Ceresit CT17 Profi is the primer that goes on first, into the wall — a deep penetrating consolidator for absorbent, dusty or friable substrates, supplied by Renders World through the exterior render primers range. It is not the grip coat that sits directly under a thin-coat finish; Henkel gives that stage to a different product, and the difference decides what to order.
What Ceresit CT17 Profi Does to an Absorbent Substrate
Ceresit CT17 Profi soaks in at 0.1–0.5 l/m², penetrates the surface and binds the aggregate grains, so the substrate is strengthened rather than merely sealed. A primed wall then takes up less water, which stops adhesive mortars, flooring, fillers and paints from overdrying while they cure. The consumption band is that wide because it tracks how thirsty the wall is: sound concrete and a crumbling internal plaster are two different jobs out of the same container.
Henkel names the substrates where Ceresit CT17 earns its keep, which is firmer ground than a generic "porous surfaces" line:
- Highly recommended — gypsum, anhydrite and aerated concrete.
- In scope — all kinds of plaster, concrete and screeds, indoors and outdoors. The English edition of the data sheet names "primers with underfloor heating installations" in that list; the Polish edition, which is newer, has "podkłady z ogrzewaniem podłogowym" — underlays and screeds carrying underfloor heating.
- Also suitable — chipboard and non-impregnated plasterboard.
- Existing paint is workable once adhesive paints have been scraped off and washed down, and strong coats ground with coarse sandpaper.
Getting the starting surface right is half the job, and the substrate matrix for brick, block and painted walls sets out where each wall type leads before any primer is opened.
Properties Henkel Declares for the CT17 Profi Primer
- Binds the aggregate, not just the dust, which is what separates a consolidating primer from a surface sealer.
- Yellow tint with a job to do — the colour exists so that work phases can be controlled by eye, which turns a walk of the elevation under good light into a genuine coverage check.
- Tiling on cement and cement-lime substrates may start after 15 minutes, using the manufacturer's CM range of adhesives.
- The Polish edition adds that the primer suits ecological, low-energy and passive-house construction; the English edition carries no equivalent sentence.
Ceresit CT17 Profi Technical Data
Two editions of the Ceresit CT17 Profi data sheet stand behind this table: the English TDS No CT17 Profi 03.24 and the Polish CT_17 Profi_KT_01.25. Where they diverge, both figures are given with their date, and the stricter one leads. Properties neither of them declares — emission class, a storage temperature range, any sub-division of the consumption band — are absent rather than estimated.
| Property | Value declared by Henkel |
|---|---|
| Base | Aqueous dispersion of synthetic resins |
| Density | Approx. 1.0 kg/dm³ |
| Consumption | 0.1–0.5 l/m², by evenness and absorption |
| Coverage, 5 l container | 10–50 m² at that band |
| Drying time | Approx. 2 hours |
| Tiling window | Approx. 15 minutes, cement substrates only |
| Application temperature | +5 °C to +25 °C, air and substrate |
| Air humidity | Below 80 % during works |
| Reference conditions | +23 °C and 50 % relative humidity |
| Application tools | Brush or roller (EN 03.24) |
| Spray application | Airless unit, PL 01.25 only |
| Dilution | 1:1 with clear water, first coat on strongly absorbent walls |
| Colour | Yellow, for control of work phases |
| Vapour permeability | Permeable; no class stated |
| Solvent content | Solvent-free |
| Packaging (EN 03.24) | 1 l, 2 l, 5 l and 10 l containers or bottles |
| Packaging (PL 01.25) | 2 l, 5 l, 10 l, 20 l canisters; 1 l bottle |
| Shelf life | 12 months from production, cool and frost-free |
| Waste code | 08 01 20 (PL edition) |
| Manufacturer | Henkel AG & Co. KGaA, Düsseldorf |
Applying CT17 Profi: Passes, Dilution and Waiting Times
Ceresit CT17 Profi arrives ready to use, so there is no mixing stage and no pot life to work against. The constraints are the state of the substrate and the weather, and Henkel names both.
- Prepare the substrate — dry, load-bearing, free of fats, bitumen, dust and any layer of poor strength.
- Grind where required — gypsum and anhydrite substrates and strong paint coats take coarse sandpaper, then thorough cleaning and vacuuming.
- Shake the container several times before the first pass.
- Apply by brush or roller, working between +5 °C and +25 °C with air humidity under 80 %. The Polish edition also permits an airless spray unit; the English edition does not name one, so brush and roller are the safer instruction for a UK site.
- Double the coat on strongly absorbent walls — the first pass diluted 1:1 with clear water, the next one undiluted. That is the Polish edition's wording; the English edition prints the same 1:1 dilution and the same undiluted follow-up.
- On floors, pour and spread evenly with a brush, without leaving puddles.
- Prime again if suction survives — where the wall is still absorbent after the coat has dried, the instruction is simply to repeat.
- Wait the right interval — 15 minutes before ceramic tiling on cement and cement-lime substrates; for every other substrate and every other top coat, until the primer is completely dry, around 2 hours.
That last interval is where programmes slip, because the 15-minute figure travels further than its scope allows: it belongs to tiling, not to render or board adhesive. On handling, the one instruction Henkel prints under PLEASE NOTE is that material in the eyes is rinsed with plenty of water, followed by medical advice. The step-by-step wall preparation method carries the full sequence for facade work.
CT17 Profi or a Quartz Key Coat — Which Stage Each Belongs To
One line in the data sheet settles more ordering questions than any other, and it is easy to miss: "For substrate priming under thin-layer plasters, apply the Ceresit CT 16 or CT 15 priming paint." Ceresit CT17 Profi, in other words, is not the key coat. A build-up that needs both gets both, and on this shelf the key-coat stage is Ceresit CT 16.
| Coat | Stage | What it does |
|---|---|---|
| CT 17 Profi | Bare absorbent substrate | Strengthens the surface, cuts absorbency |
| CT 16 | Under a thin-layer plaster | Quartz-filled key coat for the render |
On an insulated facade the sequence is easy to picture: the consolidator goes on at the very start of the wall, before the boards, and a quartz priming paint arrives much later over the cured reinforced layer, immediately beneath the silicone render. The key-coat stage has its own method and its own consumption figures, set out in the quartz primer application guide for EWI systems.
One label check is worth making on delivery. Henkel's Polish edition names a second version of the same primer, CT 17 Transparent, and directs it at priming before interior acrylic paints; the Profi version is the one written for heavy-duty preparation before tiles, floor laying and insulation boards. The word on the label, not the range name, tells you which one has arrived.
Working Out How Much CT17 Profi to Order
One container of Ceresit CT17 Profi covers a wide spread of wall, so quantities come from the substrate rather than from a rule of thumb. Renders World publishes the arithmetic with its operands — the consumption band and the pack size — so it can be re-run against any elevation:
- 5 l ÷ 0.5 l/m² = 10 m²; 5 l ÷ 0.1 l/m² = 50 m². One container therefore reaches 10–50 m².
- For 100 m²: 100 ÷ 50 = 2 containers on sound, low-suction masonry; 100 ÷ 10 = 10 containers on heavily absorbent work.
- Strongly absorbent walls take a second pass, so budget against the thirsty end of the band rather than the middle.
Where the wall type is uncertain, prime a test area first and judge the second coat from how the yellow film sits. The manufacturer's own re-prime instruction makes that a legitimate way to settle the quantity before committing to a full order.
Is CT17 Profi the Right Primer for the Job?
- Yes for dusty, friable or mixed-suction substrates ahead of adhesive, boards, screed compounds or paint — the yellow tint leaves a coverage record with no equipment at all.
- Yes for gypsum, anhydrite and aerated concrete, the three substrates singled out as highly recommended.
- No as the coat directly under a thin-layer plaster. That stage belongs to a quartz priming paint, and specifying it correctly is what makes the render bond as intended.
- Overpainting an aged facade rather than re-rendering? The 1:1 dilution before painting is declared by the manufacturer, and the silicone masonry paint options for renovation work are the finishing route from there.
Other consolidating primers sit alongside Ceresit CT17 on the Renders World shelf, and no figures are quoted for them until their own data sheets are on file. The primer comparison for UK render systems works the choice through by product type and substrate.
FAQ — Coverage, Compatibility and Application Limits
How many containers do I need for a 100 m² elevation?
The substrate decides, and the span is wide:
- Even, low-suction wall at 0.1 l/m² — one container reaches 50 m², so two containers cover the elevation.
- Very absorbent wall at 0.5 l/m² — one container reaches 10 m², so ten containers cover it.
Prime a test patch, let the yellow film show whether a second pass is coming, then order against that result.
Can it go on screeds with underfloor heating?
Yes. Underfloor-heated screeds and underlays are named in the scope of use of both editions of the data sheet, alongside all kinds of plaster and concrete, indoors and outdoors. Let the screed reach its own readiness first, then prime and allow the full drying time before the levelling compound or tile adhesive.
Does it replace a quartz key coat before render?
No, and the two are not substitutes at any point in the build-up. Ceresit CT17 Profi strengthens an absorbent substrate near the start of the wall; the quartz priming paint goes on immediately under the thin-layer render. A facade that needs both gets both, at different stages.
Why does the drying time move so much?
Because absorbency, temperature and moisture all pull on it. The declared figure of about 2 hours is measured at +23 °C and 50 % humidity, so a cool, still morning on a north elevation is worth allowing extra time for rather than crowding the next coat.
Technical Documentation for Ceresit CT17 Profi