Sika Sarnacol-2152
Two-component, solvent-free polyurethane adhesive engineered to cold-bond Sika’s Sarnafil and Sikaplan single-ply membranes to concrete, timber and CLT decks without heat or open flame.
What is it?
A two-component, solvent-free hybrid polyurethane adhesive from Sika, formulated as a filled polyol (Part A) plus an isocyanate hardener (Part B) that bonds single-ply PVC and TPO roofing membranes to the deck.
Where is it used?
Loose-lay-alternative adhered roofing build-ups on commercial, industrial, residential and infrastructure roofs where Sarnafil or Sikaplan membranes are specified and hot works are restricted.
Why use it?
It gives a cold-applied, flame-free bond with a thixotropic consistency that holds on slopes and verticals, so membranes can be adhered on live or fire-sensitive sites without a torch or hot-air welder for the bond itself.
How is it applied?
Mix A and B at 100:19 by weight for 3-5 minutes to a uniform colour, spread onto the prepared substrate at roughly 500-1,000 g/m2, then roll the membrane in within the pot life and press it home for full contact.
About Sika Sarnacol-2152
Sarnacol-2152 sits at the interface that decides whether an adhered single-ply roof performs for its full design life: the bond between the membrane and the deck. It is a two-component reactive polyurethane adhesive, supplied as a filled polyol Component A and an isocyanate hardener Component B. Once mixed, the two react and cure to a tough, flexible film that keys mechanically into the substrate and chemically to the fleece or felt backing of the membrane. Because it is solvent-free and cold-applied, there is no torch, no hot-air gun and no solvent flash-off at the bond line, which is exactly why specifiers reach for it on occupied buildings, warehouses over stored goods, and any roof where a hot-works permit is hard to secure.
In an adhered Sarnafil or Sikaplan system, Sarnacol-2152 is the component that carries wind-uplift load into the deck, so it is treated as a structural adhesive rather than a general-purpose glue. It bonds to concrete, cement mortar, plywood, timber boarding and cross-laminated timber, and is matched to fleece-backed membranes such as Sarnafil G 476 for unexposed detailing and Sarnafil G 410 L Felt for exposed roofs. For Space Arc’s contractor and consultant customers across Delhi NCR and Pan-India, it is the adhesive that lets a premium Sika membrane be installed to the manufacturer’s warranty criteria without the site constraints that torch-applied or self-adhered systems bring.
The technical insight
The performance comes from reactive polyurethane chemistry, not from a solvent drying off. When the isocyanate hardener meets the polyol, the two cross-link into a three-dimensional polymer network that grips the porous face of concrete or timber and locks onto the fleece backing of the membrane. Because the cure is a chemical reaction rather than evaporation, the film builds real cohesive and adhesive strength instead of merely tacking, and it stays flexible enough to accommodate the daily thermal movement a roof membrane sees. The thixotropic, filled consistency is deliberate: it lets the adhesive be trowelled or ridged onto sloped and detailed areas without slumping, so a consistent bead pattern and wet film are maintained where a runnier adhesive would drain away. The reaction is moisture-tolerant during placement, so light substrate dampness does not automatically ruin the bond the way it would with a purely solvent-based contact adhesive, though standing water and rain must still be avoided.
Where it is used
- Fully adhered bonding of Sarnafil and Sikaplan single-ply PVC roofing membranes to structural decks
- Cold-applied membrane installation on occupied or fire-sensitive buildings where hot works are prohibited
- Adhering fleece-backed membranes over concrete and screeded roof slabs
- Bonding membranes to plywood, timber board and cross-laminated timber (CLT) roof decks
- Detailing and upstands on adhered roofs where a thixotropic, non-slump adhesive is needed on slopes and verticals
- Warehouse, factory and logistics roofs over stored goods that cannot tolerate torch-on systems
- Institutional, commercial and residential flat-roof waterproofing using Sika single-ply systems
- Infrastructure and public-building roofs specified for warranted adhered Sika membrane build-ups
Key advantages
- Solvent-free and cold-applied, so no torch, open flame or hot-air welder is needed to form the bond
- Reactive PU cure delivers a genuinely structural, flexible bond that carries wind-uplift load into the deck
- Thixotropic consistency resists slump, giving controlled application on slopes, details and verticals
- Bonds to a wide substrate range, including concrete, cement mortar, plywood, timber and CLT
- Primer-free on most sound substrates, cutting one full trade pass off the programme
- Tolerant of light substrate moisture during placement, widening the site weather window
- Matched and warranty-compatible with Sarnafil and Sikaplan membranes as a single-source system
- Convenient pre-batched 30 kg set removes site guesswork on the mixing ratio
Limitations & considerations
- Short working time: pot life is only about 30 minutes at +20C and roughly 15 minutes at +30C, so mixed batches must be used quickly in Indian summer conditions
- Two-component product that must be mixed at the correct 100:19 ratio and blended thoroughly; hand-dosing or under-mixing weakens the bond
- Isocyanate hardener requires gloves, eye protection and adequate ventilation during handling
- Cannot be applied in rain, onto standing water, or onto frost- or dust-contaminated substrates
- Substrate must meet minimum strength (around 25 N/mm2 compressive, 1.5 N/mm2 pull-off) or the deck, not the adhesive, becomes the weak link
- Purpose-built for Sika single-ply membranes; it is not a general construction adhesive and should not be substituted into unrelated bonding tasks
Selection & best practice
Start with the deck: it must be sound, clean, dry to touch and free of laitance, dust, oil and loose material, with concrete meeting the specified strength and pull-off. Decant Component B fully into Component A and mix at 100:19 by weight with a slow-speed paddle for three to five minutes until the colour is completely uniform, scraping the sides so no unmixed streaks remain. Only mix what the crew can lay within the pot life, and cut batch size in hot weather because the working time roughly halves as temperature climbs toward +30C. Spread the adhesive evenly over the substrate at the design rate for that surface’s roughness and absorbency, then unroll the membrane into the wet adhesive and immediately press it down with a roller to wet out the fleece backing and drive out air. Protect fresh work from rain and traffic until it has gained strength, and always weld membrane seams by Sika’s normal hot-air method — Sarnacol-2152 bonds the membrane to the deck, it does not join sheet to sheet. Confirm the current version of the Sika Product Data Sheet for the exact consumption, cure and substrate figures on your project.
Specifications
| Product type | Two-component, solvent-free hybrid polyurethane adhesive |
| Components | Part A filled polyol + Part B isocyanate hardener |
| Mixing ratio | A:B = 100:19 by weight |
| Consumption | Approx. 500-1,000 g/m2 depending on substrate roughness and absorbency |
| Pot life | Approx. 30 min at +20C (approx. 15 min at +30C) |
| Application temperature | +5C to +40C (substrate and ambient) |
| Compatible membranes | Sarnafil G 476 (unexposed), Sarnafil G 410 L Felt (exposed) and matched Sikaplan membranes |
| Suitable substrates | Concrete, cement mortar, plywood, timber board, cross-laminated timber (CLT) |
| Pack size | 30 kg set (25 kg Component A pail + 5 kg Component B pail) |
| Shelf life | 12 months from date of production in unopened, correctly stored packs |
Industry use cases
Logistics & Warehousing
Adheres Sarnafil membranes to large-span warehouse and cold-store roofs where torch-on systems are barred over stored goods and racking, keeping the site fire-safe during re-roofing.
Manufacturing & Industrial
Cold-bonds single-ply membranes to factory decks so waterproofing can proceed above running production lines without a hot-works shutdown.
Commercial & Institutional
Provides a warranted adhered roof on offices, malls, hospitals and campuses where the client demands a premium Sika system with a flame-free installation.
Timber & CLT Roofs
Bonds membranes directly to plywood, timber boarding and cross-laminated timber decks on modern engineered-timber buildings that cannot tolerate open flame.
Residential High-Rise
Secures flat-roof and terrace waterproofing on occupied apartment blocks where torch application near residents is unacceptable.
Frequently asked questions
What exactly does Sarnacol-2152 bond?
Do I need a primer before applying it?
How much adhesive will I need per square metre?
How long do I have to work after mixing?
Can it be applied if the substrate is slightly damp?
Is Sarnacol-2152 in stock and can Space Arc support the roofing package?
How we position Sika Sarnacol-2152
Sarnacol-2152 is the deck-bonding adhesive within Sika’s single-ply roofing system, so it is best specified alongside the membrane it is designed for — Sarnafil G 476 for unexposed areas, Sarnafil G 410 L Felt for exposed roofs, or a matched Sikaplan membrane — with Sika’s hot-air welding accessories completing the seams. Where a project instead calls for a liquid-applied roof or complex detailing, Sika’s Sikalastic PU/PMMA membranes are the sister route from the same brand. Because this is a niche single-ply membrane adhesive, there is no equivalent product in the Fosroc range, which is centred on concrete repair, grouts and screeds rather than roofing membranes; for those scopes Space Arc supplies Fosroc separately. Our roofing specialists can help you match the correct Sarnacol, membrane grade and accessories into one warranted, single-source Sika package.
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