Sika SikaShield W1 IN
A one-part, polymer-modified cementitious adhesive that fixes SikaShield W bituminous membranes onto concrete, even when the substrate is still wet or matt-damp.
What is it?
A one-part polymer-modified cementitious adhesive (formerly SikaBit W-1), supplied as a red powder that needs only clean water added on site, engineered to bond SikaShield W wet-applied bituminous membranes to concrete.
Where is it used?
Below-ground waterproofing: basements and buried structures, horizontal RCC slabs, decks and podiums, and vertical retaining walls, across residential, commercial and infrastructure projects in Delhi NCR and Pan-India.
Why use it?
It bonds membranes cold, without torches or flame, and tolerates wet or damp concrete, so waterproofing can proceed on green or freshly cured slabs where solvent or bitumen-primer systems would fail.
How is it applied?
Mixed with a slow-speed paddle at a 0.33-0.37 water:powder ratio, spread on a saturated substrate with a 4-5 mm notched trowel, then the membrane is pressed into the wet adhesive immediately.
About Sika SikaShield W1 IN
SikaShield W1 IN is the bonding coat that holds a below-ground bituminous waterproofing system together. It is a cement-based powder, modified with polymers, that arrives in a 30 kg bag as a red powder and is brought to life on site with nothing more than clean water. Once mixed, it is trowelled onto a prepared concrete surface, and the SikaShield W bituminous sheet is laid into it while the adhesive is still wet. That single step replaces the torch-and-primer routine most contractors associate with bituminous membranes, which removes the open flame from confined basement environments and speeds up the fixing cycle considerably. Formerly sold as SikaBit W-1, the product sits at layer one of a three-part build-up: adhesive, membrane, then a protection layer before backfill.
What makes it genuinely useful on Indian sites is its tolerance for moisture in the slab. Basements, raft foundations and retaining walls are rarely bone dry when the waterproofing crew arrives, and waiting for full drying stalls the programme. SikaShield W1 IN can be applied over wet or matt-damp concrete, so the membrane can go down on green concrete that is at least three days old rather than weeks later. It needs minimal surface preparation, develops good mechanical strength, and gives a reliable bond between the bitumen sheet and the structure. For engineers and applicators, that combination of a cold process, damp-tolerant chemistry and a fast, single-component mix is what earns it a place in basement and podium tanking specifications.
The technical insight
The adhesive works because the polymer modification does two jobs at once. The cement fraction hydrates and grips the concrete substrate the way any cementitious product does, while the added polymers give the cured film flexibility and, crucially, an affinity for the bituminous face of the membrane, which a plain sand-cement slurry would never wet out or hold. Because the bond is built on cement hydration rather than solvent evaporation, water in the substrate is not an enemy but part of the mechanism, which is why the product is designed to be applied onto a deliberately saturated surface and onto damp concrete. The membrane must be embedded while the adhesive is still wet so both faces knit together before the mix stiffens; the pot life of at least 30 minutes at 25 C sets the working window. Getting the water dose right matters more than with most products, because over-watering past the 0.37 ratio permanently weakens the cured mechanical strength, and a mix that has thickened must be discarded rather than re-tempered.
Where it is used
- Bonding SikaShield W bituminous membranes in basements and other below-ground structures
- Membrane fixing on horizontal reinforced concrete slabs, podiums and parking decks
- Adhering waterproofing membranes to vertical reinforced concrete retaining walls
- Foundation and raft waterproofing on infrastructure and commercial projects
- Plinth and basement tanking on residential buildings
- Cold, flame-free membrane installation in confined or fire-sensitive spaces
- Waterproofing over green or freshly cured concrete that is at least three days old
- Membrane bonding onto matt-damp concrete where drying time is not available
Key advantages
- Cold, flame-free bonding removes the fire and fume risk of torch-on membrane systems in basements
- Tolerates wet and matt-damp concrete, so work is not held up waiting for slabs to dry out
- One-part powder needs only clean water, avoiding two-component measuring errors on site
- Requires minimum surface preparation compared with primer-based membrane systems
- Develops good mechanical strength and a reliable bond between bitumen sheet and concrete
- Simple notched-trowel application that most waterproofing crews can execute quickly
- Pot life of at least 30 minutes gives a practical working window per batch
- Part of a complete, warrantied SikaShield W membrane system rather than a stand-alone patch
Limitations & considerations
- It is an adhesive only, not a waterproofing layer in itself; it must be used with a SikaShield W membrane and protection layer
- The membrane must be laid into the adhesive while it is still wet, which demands coordinated mixing and fixing on site
- Working temperature is limited to +10 C to +40 C for both ambient air and substrate
- Over-adding water beyond the 0.33-0.37 ratio permanently reduces cured mechanical strength, so dosing must be controlled
- A batch that has stiffened cannot be re-tempered with water and must be thrown away
- Backfilling must wait a minimum of 24 hours of curing at +25 C, which the site programme has to allow for
Selection & best practice
Start with sound concrete: at least 3 days old, uniform, firm, clean and free of laitance, grease, oil, dust and any sharp burrs that could puncture the membrane. Mix with a slow single-paddle mixer under 400 rpm, always adding powder to water, and hold to the 0.33-0.37 water:powder ratio (about 9.9-11.1 litres per 30 kg bag). Mix for three minutes, stand for one, then remix for one more. Saturate the substrate with clean water first, spread the adhesive with a 4-5 mm notched trowel at 1-3 mm thickness, and press the SikaShield W membrane in immediately while the adhesive is wet. Plan crew size so fixing keeps pace with the 30-minute pot life, discard any batch that has thickened, and protect the finished membrane, allowing a minimum 24 hours cure at +25 C before backfilling. Clean tools with water straight after use.
Specifications
| Chemical base | Polymer-modified cement (1-part) |
| Appearance / colour | Red powder |
| Packaging | 30 kg bag |
| Mixing ratio | Water : powder = 0.33-0.37 (~9.9-11.1 L water per 30 kg bag) |
| Fresh mortar density | ~1.95 kg/L (EN ISO 2811-1) |
| Consumption | ~2.0-3.0 kg/m2 of wet adhesive per m2 of membrane |
| Layer thickness | 1 mm min. to 3 mm max. |
| Pot life | ≥ 30 minutes (100 g, +25 C, 65% r.h.) |
| Ambient / substrate temperature | +10 C min. to +40 C max. |
| Shelf life / storage | 12 months; store dry at +5 C to +35 C in sealed packaging |
Industry use cases
Commercial basements
Tanking multi-level basement walls and rafts where torch-on membranes are unwelcome in confined, poorly ventilated spaces; the cold, damp-tolerant bond lets the crew work on green concrete.
Podiums and parking decks
Bonding SikaShield W membranes to horizontal RCC podium slabs and deck areas before screed and landscaping, protecting occupied space below.
Infrastructure foundations
Waterproofing raft foundations, pile caps and retaining walls on metro, tunnel and large civil works where fast, flame-free membrane fixing keeps the programme moving.
Residential buildings
Basement, plinth and lift-pit waterproofing on housing and apartment projects, where a one-part water-mixed adhesive suits smaller crews and quicker turnarounds.
Retaining and buried walls
Adhering membranes to vertical concrete retaining walls before backfill, with a minimum 24-hour cure protecting the bond against soil and hydrostatic load.
Frequently asked questions
Is SikaShield W1 IN a waterproofing membrane on its own?
Can it really be applied on wet or damp concrete?
What was this product called before?
How much adhesive do I need per square metre?
How long before I can backfill against the membrane?
What happens if the mix gets too thick or too much water is added?
How we position Sika SikaShield W1 IN
SikaShield W1 IN only makes sense as part of the SikaShield W system, so it is naturally specified alongside the SikaShield W159 ED 1.5 mm wet-applied bituminous membrane it is designed to bond, with a suitable protection layer above before backfill. Where a self-adhered approach is preferred, the SikaShield E50 HDPE SA IN membrane is the range alternative. For detailing around the waterproofing, we pair it with SikaSwell A swellable profiles at construction joints and SikaTop Armatec-110 EpoCem as a bonding and reinforcement-protection coat. Because Space Arc also carries Fosroc, contractors who prefer a torch-applied route for the same below-ground problem can consider the Fosroc Proofex Torchseal system as a different means to the same end. Talk to our technical team about which build-up suits your substrate, site fire constraints and programme.
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