Description
Ceresit CT84 Express 850 ml is the gun-applied polyurethane foam adhesive that bonds EPS and XPS insulation boards up to 10 m² per canister, reaches mechanical-fixing strength in around 2 hours, and cures reliably down to −10 °C once applied. It replaces the 25 kg cement bag and the mixing station with a single lightweight canister and an applicator gun.
This product sits within the professional EPS adhesives and basecoats range at Renders World and bonds boards from the EPS insulation boards collection across fast-track facade work, cold-season programmes, and "insulation on insulation" retrofit upgrades.
Where Ceresit CT84 Performs Best — Fast-Track Facade EPS Bonding
Ceresit CT84 turns a four-day cement-bonded elevation into a one-day foam-bonded one by reaching mechanical-fixing strength in around two hours, which is the figure that defines the product's role on every fast-track facade programme it specifies into. A wall bonded in the morning is ready for anchor installation by lunch and basecoat the next day.
- Fast-track new-build and retrofit facade work — programmes where the 24-hour wait imposed by certified cement adhesives would stall the next trade, particularly on multi-elevation jobs running multiple lifts in parallel.
- Cold-season EWI between October and March — overnight temperatures that threaten cement cure are the conditions the polyurethane chemistry handles confidently, extending the practical UK installation season into shoulder months.
- "Insulation on insulation" retrofit upgrades — adding new EPS over an existing insulated facade without loading the substrate with cement-bag weight or driving a fresh mixing station onto a constrained site.
- Scaffolded jobs above two lifts — hauling 850 ml canisters up the scaffold is a fraction of the labour cost of 25 kg cement bags, and the logistics saving compounds over a multi-storey programme.
Why Trade Specifiers Choose Ceresit CT84
- 10 m² per 850 ml canister — one canister covers approximately 20 standard EPS boards, replacing a 25 kg cement bag at roughly a tenth of the haul weight up the scaffolding.
- 2-hour time to mechanical fixing — anchors can be installed approximately two hours after board placement at typical site temperatures, against the 24-hour minimum that certified cement systems require — a full working day saved per elevation pass.
- Cold-cure resilience to −10 °C — application proceeds from 0 °C upwards, and once the bead is laid the foam continues to cure reliably even if overnight temperatures drop sharply.
- λ 0.040 W/mK matches EPS — the cured foam carries the same thermal conductivity as the board it bonds, so the bead lines do not act as cold bridges in the way that traditional cement dabs can on poorly executed installations.
- Waterless, electricity-free application — the applicator gun runs straight from the canister; no water supply, no mixing paddle, no power tools — the cleanest adhesive option on confined urban sites.
- Doubles as a thermal gap-filler — the same canister fills small gaps between adjacent boards as installation proceeds, eliminating cold-bridging at board joints without switching products mid-workflow.
Technical Specifications — Ceresit CT84 Data
| Property | Value |
|---|---|
| Product type | Single-component polyurethane (PU) foam adhesive, gun-applied |
| Pack size | 850 ml pressurised canister |
| Coverage yield | Up to 10 m² per canister (≈ 20 standard EPS boards) |
| Application temperature | 0 °C to +40 °C (substrate and ambient) |
| Cure resilience after application | Continues curing down to −10 °C |
| Tack-free time | ≈ 10 minutes |
| Time to mechanical fixing | ≈ 2 hours at +20 °C |
| Thermal conductivity (λ) | 0.040 W/mK (matches EPS) |
| Application method | Professional PU applicator gun |
| Compatible substrates | Concrete, brick, ceramic block, sound render, timber, OSB |
| Compatible boards | EPS, graphite EPS, XPS (mineral wool with appropriate primer on Express STD per TDS) |
| Shelf life | ≈ 12 months, sealed canister, stored upright at 5–25 °C |
The 10 m² facade yield is the figure that drives ordering at the elevation scale. Twelve canisters per 100 m² absorbs the 15–20 % wastage that comes with cooler weather, small-area repairs, and bead loss at board cuts around openings.
How to Apply Ceresit CT84 — Perimeter-and-W Bead Pattern
Shake the canister vigorously for around 30 seconds, screw it into a professional PU applicator gun, and trigger a short test bead onto waste material to clear the nozzle. The facade bead pattern is consistent across every board: a continuous perimeter ribbon plus one central pass that seats the board evenly without ribbons running off as the foam expands.
- Perimeter ribbon — apply a continuous bead roughly 2–3 cm in from the board edge on all four sides; this seals the board against air bypass and provides the load path for the mechanical anchor pattern installed later.
- Single W-shaped pass — run one W-shaped bead across the centre of the board; the geometry delivers full contact without point-load gaps under the board face.
- Board placement window — press the board firmly against the wall within around 5 minutes of bead application, sliding 2–3 cm into final position to seat the bead lines evenly while the foam is still soft.
- Mechanical anchor timing — pin approximately 2 hours after board placement at +20 °C; in cooler conditions extend to 3–4 hours before drilling, so the pin holds best in a fully cured bead.
Once the boards are anchored, the elevation is ready for the reinforced basecoat layer. The basecoat and mesh reinforcement layer guide covers the next-stage detail across overlaps, corners, and openings.
Installation Notes — Substrate Conditions, Canister Storage, Gun Discipline
Apply CT84 in dry conditions with substrate and ambient temperatures at or above 0 °C. The bead must contact a dry surface — standing water on the substrate or board face interrupts the polyurethane reaction at the interface and the bond never reaches full strength. Direct sunlight on the bead before the board is placed is the most common cause of partial cures, so work on the shaded face of the elevation in the morning and rotate to the sunlit face once it falls into shadow later in the day.
Store canisters upright between 5 °C and 25 °C in a frost-free, well-ventilated area. Canisters that have spent the night in a cold van warm up slowly and dispense unevenly until they reach working temperature, so bring them inside the night before a winter installation day.
- Leave the gun attached between uses on the same job — removing the gun mid-canister allows the residual foam in the valve to cure and seizes the next dispense.
- Test bead at the start of every session — trigger a short bead onto waste material to confirm consistent dispense before the first board of the day or after any break longer than an hour.
- Clean uncured residue promptly — Ceresit PU Cleaner or acetone removes wet foam; once cured, removal is mechanical only and difficult on visible finishes.
Pro Tips From UK Installers Using Ceresit CT84
The 2-hour figure on the data sheet is the headline, but the practical programme gain comes from the small site habits that keep every canister dispensing at full yield and every board seating evenly.
- Warm the canister before the first bead — a canister stored overnight at 5 °C dispenses slowly and short of yield for the first minute; hold it under a jacket for ten minutes before the day's first board to recover full coverage on the early run.
- Slide, do not slap, the board home — press the board against the wall and slide it 2–3 cm into final position while the foam is still soft; this seats the bead evenly and corrects minor alignment without bouncing the board off the bead crown.
- Plan the bead toward the down-slope edge on tapered work — on steeply pitched or tapered elevations, position the perimeter bead slightly toward the lower edge so foam expansion travels away from the joint above, not into it; this keeps the upper joint clean for the next board.
- Stage one fresh canister per lift — a canister run dry mid-board is the most common cause of weak corner bonds; stage a fresh canister on every lift before the day starts rather than chasing replacements from the ground.
Is Ceresit CT84 Right for Your Project?
- Ideal for fast-track and cold-season EPS facade work — choose CT84 where programme speed, cold-season working, scaffold weight, or "insulation on insulation" retrofit drives the decision, and the substrate is flat enough that a foam bead reaches full contact without bridging.
- For plinth, DPC, and below-grade XPS work — the XPS-tuned CT84 variant at the same 850 ml pack delivers the same gun-applied workflow with formulation tuned for the dense closed-cell boards used at ground-contact zones; pair the two products across the elevation for a fully foam-bonded build-up.
- For substrate deviations over 20 mm — foam adhesive cannot level the kind of substrate undulation that a notched-trowel cement adhesive absorbs; switch to Atlas Hoter U Grey 25 kg cement adhesive on rougher elevations, then return to CT84 where the substrate is sound.
- For the foam-vs-cement decision in detail — the foam adhesive versus traditional cement comparison walks through cost-per-m², programme implications, and substrate tolerance side by side.
FAQ — Ceresit CT84 Coverage, Compatibility, Ordering
How many canisters of CT84 are needed per 100 m² of EWI?
At the rated yield of approximately 10 m² per 850 ml canister, a 100 m² elevation consumes around 10 canisters for board bonding alone. Order 12 canisters per 100 m² to absorb the 15–20 % wastage that comes with cooler weather (which reduces yield), partially used canisters on small repair zones, and bead waste at board cuts around openings. Scale linearly for larger elevations and add a flat 5 % buffer on multi-storey programmes where mid-board canister changes are more disruptive.
How soon after board placement can mechanical anchors be installed?
The standard figure is approximately two hours at +20 °C, which is the point the foam has cured firm enough to hold the board against the wind-load pressures that pinning generates. In cooler conditions extend to 3–4 hours, and in genuinely cold weather close to 0 °C application temperature wait until the bead is fully firm before drilling. The boards stay in place either way, but the pin holds best in a fully cured bead, and rushing the timing on a cold morning is the most common cause of pin pull-through showing up at handover.
When should I choose CT84 over a traditional cement adhesive?
Choose CT84 where programme speed, cold-season working, scaffolding weight, or clean-site logistics drive the decision and the substrate is flat enough to bond without bridging. Cement adhesives still win where substrate deviations exceed 20 mm, where the basecoat stage uses the same product as the bonding stage in a 2-in-1 workflow, or where the lowest possible cost-per-m² beats the programme speed advantage. The EPS adhesive selection guide covers the full decision tree across system specifications.
Can CT84 bond mineral wool boards?
Standard CT84 is engineered and certified for EPS, graphite EPS, and XPS. Mineral wool has different vapour permeability and slab-weight characteristics that are better served by a dedicated wool-rated adhesive. The CT84 Express STD variant carries an extended certification path for mineral wool with the correct primer applied first, but on routine UK projects a cement-based wool adhesive remains the simpler and more widely warranted specification.
Does CT84 work as a gap-filler between boards as well as a bonding adhesive?
Yes. The same canister fills small gaps between adjacent boards as installation proceeds, eliminating cold bridging at board joints without switching to a separate gap-fill foam. Trim any cured foam proud of the board face with a sharp blade before the basecoat stage, so the reinforced layer trowels flat across the elevation. Gap-filling consumes only a fraction of canister yield over a full installation, so the 12-canister-per-100 m² ordering allowance covers it without separate calculation.
How should canisters be stored and disposed of on a UK EWI project?
Store canisters upright between 5 °C and 25 °C, away from direct sunlight and frost — bring them indoors overnight on winter jobs so they dispense at full yield in the morning. Spent canisters are pressurised metal waste that the site waste carrier collects separately for licensed recycling. The transport weight saving versus the cement bag equivalent lowers the delivery carbon footprint by a meaningful margin on every elevation, particularly on multi-storey programmes where the haul weight differential compounds across every lift.
Technical Documentation — Ceresit CT84 TDS