Sika SikaShield Primer W-30 IN
A low-odour, water-based bituminous primer that activates the deck and locks SikaShield APP and SBS membranes tight to concrete, screed and lime-concrete.
What is it?
A single-component, water-based modified bituminous primer that penetrates and activates the substrate ahead of preformed bituminous sheet membranes.
Where is it used?
On concrete decks, screeds, lime-concrete and porous stone substrates that will receive SikaShield torch-on or self-adhesive APP/SBS membranes.
Why use it?
It builds a tacky, dust-free bituminous film so membranes fuse or self-stick reliably, while staying low-odour for occupied and enclosed sites.
How is it applied?
Dilute with 20-50% clean water, then apply one coat by brush, roller or spray and allow it to dry before laying the membrane.
About Sika SikaShield Primer W-30 IN
SikaShield Primer W-30 IN sits at the start of a torch-on or self-adhesive waterproofing system, and although it is only one thin coat, it decides how well the rest of the build-up performs. It is a single-component, water-based primer built on a bitumen, water and additive base. Once brushed or sprayed onto a prepared deck it soaks into the surface pores, binds loose dust, and leaves behind a compatible bituminous film that the incoming membrane can grip. Sika formulated this grade specifically for tropical and Indian site conditions, so it dries quickly even in warm weather and is forgiving to apply on the kind of open terraces, podiums and basement rafts common on projects here.
Because it carries no solvent, the primer stays low in odour, which is the practical reason many contractors reach for it on occupied commercial buildings, hospitals, hotels and enclosed plant rooms where a solvent-based primer would clear the floor. It is engineered to work hand-in-glove with the SikaShield range of APP and SBS modified membranes, whether they are heat-bonded with a torch or laid as self-adhesive sheets. The result is a cleaner, faster first day on site: the deck is primed in the morning, the film is touch-dry within hours, and the membrane crew can begin laying the same working day rather than waiting overnight.
The technical insight
A bituminous membrane is only as good as the bond between its underside and the deck, and raw concrete rarely offers that bond on its own. A green or dusty slab is alkaline, chalky and full of open pores, so molten or self-adhesive bitumen laid straight onto it tends to sit on a weak, dusty skin that later peels. SikaShield Primer W-30 IN solves this by wetting into those pores as an emulsion, then breaking as the water evaporates to deposit fine bitumen droplets that coalesce into a continuous, slightly tacky film chemically matched to the membrane above. That film does three jobs at once: it seals and consolidates the loose surface dust, it presents a like-to-like bituminous surface so the membrane fuses or sticks to bitumen rather than to concrete, and it improves the effective contact area across an uneven trowelled screed. Diluting with 20-50% clean water is not optional detail — it lets the emulsion penetrate instead of skinning over on top, which is why over-thick, undiluted application actually reduces adhesion. Keeping substrate moisture below 6% matters for the same reason: trapped water under a sealed film later drives blisters when the deck warms.
Where it is used
- Priming concrete roof decks before SikaShield torch-on APP or SBS membranes
- Preparing screeds and lime-concrete substrates in podium and terrace waterproofing
- Low-odour priming of slabs in occupied commercial buildings, hospitals and hotels
- Basement raft and retaining-wall priming ahead of self-adhesive bituminous sheets
- Re-priming aged bituminous surfaces during roof refurbishment and re-membraning
- Priming porous natural stone and masonry substrates that will receive sheet membranes
- Balcony and wet-area substrate preparation on residential projects
- Priming enclosed plant rooms and shafts where solvent emissions must be avoided
Key advantages
- Water-based and low in odour, so it can be used on occupied and poorly ventilated sites
- Quick-drying, touch-dry in about four hours, letting membranes go down the same day
- Bonds well to concrete, screed, porous stone and lime-concrete substrates
- Adheres to aged bituminous surfaces, making it practical for refurbishment work
- Single-component and ready to use after a simple dilution with clean water
- Applies easily by brush, roller or spray for fast coverage on large decks
- Formulated for tropical and Indian climate conditions
- Compatible across the SikaShield APP and SBS membrane range for a warranted system
Limitations & considerations
- Water-based, so it must not be applied over damp substrates with moisture above 6% or it can blister
- Requires ambient and substrate temperatures between +10 C and +40 C; drying slows in cold, humid conditions
- Must be diluted correctly (20-50% water) — undiluted, over-thick application reduces penetration and adhesion
- Rain before the film has fully cured can wash off or damage the primer, so it needs a dry weather window
- It is a priming layer only, not a standalone waterproofing coating, and must be overlaid with a membrane
- Full membrane adhesion depends on the primer being properly dry, not just touch-dry, before torching
Selection & best practice
Start with a sound substrate: the deck must be clean, structurally sound and free of laitance, oil, curing compound and loose dust, with moisture content below 6%. Repair honeycombing and form proper fillets at upstands first. Stir the primer, then dilute with 20% to 50% clean water depending on how porous and rough the surface is — rougher, thirstier screeds take more water so the primer soaks in rather than sitting on top. Apply one even coat by brush, roller or spray, working it into the pores and avoiding puddles or over-thick pooling. Work only within +10 C to +40 C and plan around a dry weather window so no rain hits the film before it cures. Allow it to reach touch-dry (about 4 hours) and ideally hard-dry (up to 6 hours) on concrete before laying the SikaShield membrane; on colder or more humid days allow longer. Consumption runs 0.200-0.400 kg/m per coat once diluted, so estimate stock from the deck area and its porosity. Always cross-check the current Sika Product Data Sheet and Safety Data Sheet for the batch on your site.
Specifications
| Product type | Single-component, water-based modified bituminous primer |
| Base | Bitumen, water and additives |
| Colour / appearance | Black or brown pasty liquid |
| Density | approx. 1.00 +/- 0.05 g/mL at +27 C |
| Solids content | 45 +/- 5 % by weight |
| Dilution | 20% to 50% clean water |
| Consumption | 0.200-0.400 kg/m per coat (diluted) |
| Touch / hard dry (concrete) | Touch-dry approx. 4 h; hard-dry up to 6 h |
| Application temperature | +10 C to +40 C (ambient and substrate); substrate moisture below 6% |
Industry use cases
Commercial and institutional buildings
Its low-odour, water-based nature lets crews prime occupied floors in hospitals, hotels and offices without evacuating the space for solvent fumes.
Residential terraces and podiums
Used to prime screeds and lime-concrete on terrace and podium decks before SikaShield membranes, giving apartments a reliable waterproof base.
Roof refurbishment
Bonds to aged bituminous surfaces, so it re-primes tired roofs during re-membraning without full removal of the old bitumen skin.
Basements and retaining structures
Primes raft slabs and retaining walls ahead of self-adhesive or torch-on sheets in below-grade tanking work.
Enclosed plant rooms and shafts
Chosen for lift pits, service shafts and plant rooms where poor ventilation rules out solvent-based primers.
Frequently asked questions
Is SikaShield Primer W-30 IN solvent-based or water-based?
How much do I need to dilute it before use?
How long before I can lay the membrane over it?
How much primer will one coat cover?
Can I use it to re-prime an old bituminous roof?
Which membranes is it meant to be used with?
How we position Sika SikaShield Primer W-30 IN
SikaShield Primer W-30 IN is the water-based primer to specify at the head of a SikaShield membrane system, and it belongs to the same family as the SikaShield APP and SBS torch-on and self-adhesive membranes it is designed to bond — always pair it with a SikaShield sheet rather than mixing primer and membrane across brands. Where a project prefers a solvent/cold-applied primer on open decks, or is already standardised on a Fosroc Proofex Torchseal membrane build-up, Fosroc Torchseal Primer M is the natural equivalent. Space Arc supplies both systems and can match the primer to the membrane and site conditions you are working with. For projects that call for liquid-applied waterproofing instead of sheet membranes — such as complex, detail-heavy roofs — our Fosroc Brushbond RFX acrylic cementitious coating is the alternative route to a watertight deck.
Fosroc Torchseal Primer M — A specifier may choose the Fosroc primer when the deck is open and well-ventilated, or when the roof is already being built as a Fosroc Proofex Torchseal system and single-brand compatibility is preferred.
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