Description
Ceresit CT84 Express 850 ml is the gun-applied polyurethane foam adhesive that bonds EPS and XPS insulation boards at up to 10 m² per canister, reaches mechanical-fixing strength in around 2 hours, and continues curing 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.
Where Ceresit CT84 Performs Best — Fast-Track Facade EPS Bonding
Ceresit CT84 is the polyurethane foam adhesive that turns a four-day cement-bonded elevation into a one-day foam-bonded one, reaching mechanical-fixing strength in around two hours rather than the 24 a certified cement system needs. It sits within the professional EPS adhesives and basecoats range at Renders World, and the technical desk can confirm where the foam route beats cement on any given elevation. A wall bonded in the morning is ready for anchors by lunch and basecoat the next day.
- Fast-track new-build and retrofit facade work — programmes where the 24-hour cement-cure wait would stall the next trade, particularly on multi-elevation jobs running several 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 season into the 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 mixing station onto a constrained site.
- Scaffolded jobs above two lifts — hauling 850 ml canisters up the scaffold costs a fraction of the labour 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 roughly 20 standard EPS boards, replacing a 25 kg cement bag at about a tenth of the haul weight up the scaffolding.
- 2-hour time to mechanical fixing — anchors can be installed around two hours after board placement at typical site temperatures, against the 24-hour minimum 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 bead lines do not act as cold bridges the way poorly executed cement dabs can.
- Waterless, electricity-free application — the applicator gun runs straight from the canister with no water supply, mixing paddle, or power tools, making it the cleanest adhesive option on confined urban sites.
- Doubles as a thermal gap-filler — the same canister fills small gaps between adjacent boards as work proceeds, eliminating cold-bridging at 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 primer on Express STD per TDS) |
| Shelf life | ≈ 12 months, sealed canister, stored upright at 5–25 °C |
How to Apply Ceresit CT84 — Perimeter-and-W Bead Pattern
Shake the canister for around 30 seconds, screw it into a professional PU applicator gun, and trigger a short test bead onto waste to clear the nozzle. The facade bead pattern stays 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, sealing the board against air bypass and providing the load path for the later anchor pattern.
- Single W-shaped pass — run one W-shaped bead across the centre; the geometry delivers full contact without point-load gaps under the board face.
- Board placement window — press the board firmly within around 5 minutes of bead application, sliding 2–3 cm into final position to seat the bead lines while the foam is still soft.
- Mechanical anchor timing — pin about 2 hours after placement at +20 °C; in cooler conditions extend to 3–4 hours 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, since 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 the shaded face in the morning and rotate to the sunlit face once it falls into shadow.
Store canisters upright between 5 °C and 25 °C in a frost-free, ventilated area, and bring them inside the night before a winter installation day, since a canister that has spent the night in a cold van dispenses unevenly until it reaches working temperature.
- Leave the gun attached between uses on the same job — removing it mid-canister lets residual foam in the valve cure and seizes the next dispense.
- Test bead at the start of every session — trigger a short bead onto waste to confirm consistent dispense before the first board 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.
How CT84 EPS Foam Compares to the CT84 XPS Foam Sibling
Both CT84 foams share the same polyurethane base, gun workflow, and cold-cure performance, so the decision is which board surface and zone each is tuned for. Matched across the elevation, they bond the whole build-up from foundation to field.
| Variant | Key Spec | When to Choose |
|---|---|---|
| CT84 EPS Foam 850 ml | EPS surface · ≈10 m²/can facade | Fast-track EPS field elevations above DPC |
| CT84 XPS Foam 850 ml | XPS surface · ≈14 m²/can foundation | Plinth, below-DPC, bituminous, damp |
Where substrate undulation exceeds what a foam bead can bridge, Atlas Hoter U Grey 25 kg absorbs the deviation as a notched-trowel cement adhesive, then hand back to CT84 where the substrate is sound.
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 delivers the same gun-applied workflow formulated for dense closed-cell boards at ground-contact zones; pair the two across the elevation.
- For substrate deviations over 20 mm — foam cannot level the undulation a notched-trowel cement adhesive absorbs, so switch to Atlas Hoter U Grey 25 kg on rougher elevations and return to CT84 where the wall is sound.
- Bond the matched boards — the foam bonds graphite EPS from the EPS insulation boards collection, ready to pair on one order.
FAQ — Ceresit CT84 Coverage, Compatibility, Ordering
How many canisters of CT84 are needed per 100 m² of EWI?
At the rated yield of about 10 m² per 850 ml canister, a 100 m² elevation consumes around 10 canisters for board bonding alone. Order 12 per 100 m² to absorb the 15–20% wastage from cooler weather, 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 about two hours at +20 °C, the point the foam has cured firm enough to hold the board against the wind-load pressures pinning generates. In cooler conditions extend to 3–4 hours, and close to 0 °C wait until the bead is fully firm before drilling. The boards stay put 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 at handover.
When should I choose CT84 over a traditional cement adhesive?
Choose CT84 where programme speed, cold-season working, scaffold 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 a 2-in-1 workflow uses one product for bonding and basecoat, or where the lowest cost-per-m² beats the 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 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, though on routine UK projects a cement-based wool adhesive remains the simpler and more widely warranted specification, subject to the system certificate.
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 work proceeds, eliminating cold bridging at joints without a separate gap-fill foam. Trim any cured foam proud of the board face with a sharp blade before basecoat so the reinforced layer trowels flat. Gap-filling uses only a fraction of canister yield, so the 12-canister-per-100 m² 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, and bring them indoors overnight on winter jobs so they dispense at full yield in the morning. Spent canisters are pressurised metal waste the site carrier collects separately for licensed recycling, and the transport weight saving versus the cement-bag equivalent lowers the delivery footprint on every elevation, particularly on multi-storey programmes where the haul differential compounds across each lift.
Technical Documentation — Ceresit CT84 TDS