Sika Sika-1
A time-tested liquid integral waterproofing admixture that seals cement mortar and concrete from the inside, blocking capillary water while letting the structure breathe.
What is it?
A chloride-free liquid admixture that is mixed into gauging water so waterproofing becomes an integral property of the mortar or concrete itself, rather than a surface coat.
Where is it used?
Water tanks, basements, roof screeds, plinth beds, swimming-pool renders and retaining-wall plasters where dampness and seepage need to be controlled at source.
Why use it?
It reduces the permeability of the matrix, improves workability at a lower water-cement ratio and cuts shrinkage cracking, giving denser, more durable concrete and plaster.
How is it applied?
Dosed into the mix water at 0.3-0.5 litres per 50 kg cement for mortar or 1-2 litres per cubic metre for concrete, then batched and placed as normal.
About Sika Sika-1
Sika-1 is one of the oldest and most widely specified integral waterproofing admixtures used on Indian sites, and it remains a dependable first line of defence against dampness in mortar and concrete. Rather than sitting on top of a surface the way a membrane or coating does, Sika-1 is added to the gauging water so that its action is distributed throughout the mix. The result is a mortar or concrete that carries its own resistance to water movement, which is exactly what engineers want in a plaster bed, a screed or a structural pour that has to stay dry over its full thickness.
The admixture works on two fronts at once. Part of it reacts with the products of cement hydration to form insoluble compounds that block the fine pores and capillaries through which water otherwise travels; the balance acts as a plasticiser that lets the crew place a workable mix at a lower water-cement ratio. Because it is chloride-free, Sika-1 is suited to reinforced sections without the corrosion concerns that dog older salt-based compounds. For contractors and consultants it fits neatly into normal batching practice, needing no special equipment, no primer and no change to the placing sequence.
The technical insight
Concrete and cement mortar are never fully solid; as the cement hydrates and bleed water migrates out, it leaves behind a network of fine pores and capillaries. Under a head of water or persistent dampness, that network is the highway along which moisture creeps through a slab or wall. Sika-1 attacks this on two levels. Its reactive fraction combines with free lime and other hydration products to precipitate insoluble crystalline material inside the capillaries, physically narrowing and blocking them so liquid water can no longer pass, while the structure still breathes as vapour. At the same time its plasticising action lets the same slump be achieved with 3-6% less water, and since capillary porosity is driven largely by excess mix water, cutting the water-cement ratio makes the hardened matrix inherently denser and less permeable. The two mechanisms reinforce each other: fewer, finer capillaries to begin with, and those that remain are chemically choked.
Where it is used
- Render and plaster coats to overhead and underground water-storage tanks
- Screeds and mortar beds for roof waterproofing at plinth and terrace level
- Internal and external basement wall plasters exposed to soil moisture
- Swimming-pool render coats behind tiling
- Retaining-wall plaster where damp ground bears against the back face
- Repair and patch mortars where a dense, low-permeability finish is required
- Concrete for water-retaining and water-excluding structures as part of a wider mix design
- Floor and wall screeds in wet areas such as bathrooms, kitchens and utility ducts
Key advantages
- Waterproofing is built into the full thickness of the mortar or concrete, not just a surface skin
- Chloride-free formulation is safe to use in reinforced concrete
- Plasticising action allows a lower water-cement ratio, giving denser, stronger concrete
- Reduces shrinkage and the risk of hairline cracking that lets water in
- Improves workability, making placing and compaction easier for the crew
- Mixes straight into the gauging water with no special plant or primer
- Compatible with ordinary Portland and blended cements used across Indian sites
- Long, proven track record on Indian projects, familiar to most site engineers
Limitations & considerations
- It is an admixture, not a membrane; it cannot bridge cracks or seal construction joints on its own
- It does not compensate for poor workmanship, over-watering, honeycombing or inadequate compaction
- For structures under significant hydrostatic head, it should be combined with a positive-side membrane or coating rather than relied on alone
- Dosage must be controlled by measure; guessing on site undermines both waterproofing and strength
- It reduces permeability but does not make concrete fully impervious against a standing water head over long durations
- Performance depends on correct curing; the mix still needs proper moist curing to develop its dense matrix
Selection & best practice
Add Sika-1 to the measured gauging water before it is combined with the cement and aggregate, never to the dry mix, and stir so it disperses evenly. Keep the total water content down: use the admixture to gain workability, not as licence to add more water, since the water-cement ratio is what governs the final density. For plasters and renders, apply in the specified number of coats over a well-prepared, roughened background and cure each coat thoroughly. On water-retaining or below-grade work, treat Sika-1 as one layer of a system: pair it with sound detailing at joints, a crack-free structural mix and, where a real water head exists, a dedicated membrane or crystalline coating. Always follow the current Sika technical data sheet for the exact dosage and mixing sequence on your grade of work.
Specifications
| Product type | Liquid integral waterproofing and permeability-reducing admixture |
| Base | Aqueous, chloride-free formulation |
| Dosage (mortar) | 0.3-0.5 litres per 50 kg cement |
| Dosage (concrete) | 1-2 litres per cubic metre of concrete |
| Water reduction | Approximately 3-6% |
| Chloride content | Chloride-free |
| Relevant standard | Integral waterproofing compounds to IS 2645 (Indian market) |
| Pack sizes | 1 litre, 5 litre and 20 litre containers |
Industry use cases
Residential & buildings
Terrace screeds, bathroom and kitchen floor beds and external wall plasters where everyday dampness and seepage must be kept out of habitable space.
Water infrastructure
Render and mortar coats to overhead and underground water tanks, sumps and treatment structures that have to stay watertight in daily service.
Basements & below-grade
Basement wall and floor plasters against soil moisture, used together with a membrane where a genuine water head is present.
Swimming pools & wet areas
Dense, low-permeability render coats behind pool tiling and in fountains, water bodies and other permanently wet zones.
Repair & maintenance
Patch and repair mortars on old damp walls and parapets where a denser, water-resisting finish is needed as part of a rehabilitation job.
Frequently asked questions
Is Sika-1 a waterproofing coating or an admixture?
How much Sika-1 do I add?
Does it contain chloride and is it safe for RCC?
Can Sika-1 stop seepage in a deep basement on its own?
Will it let me add more water to make the mix easier to place?
What pack sizes does Space Arc supply and where do you deliver?
How we position Sika Sika-1
Sika-1 is the workhorse liquid admixture in Sika’s integral waterproofing range and is the natural starting point for damp-proofing plasters, screeds and general concrete. Where the specification calls for an IS 2645 compliant liquid product with a formal test certificate, SikaCim from the same Sika family is the closely related option to reach for. For jobs that face a genuine water head rather than simple dampness, treat Sika-1 as one layer of a system and pair it with a Sika positive-side membrane or crystalline coating; our team can also cross-map it to equivalent products from Fosroc, Dr. Fixit and MC-Bauchemie in our range if a project is standardised on another brand.
Fosroc Conplast X421IC — A specifier already standardised on Fosroc, or one who wants a lignosulphonate-based liquid admixture with a stated IS:2645-2003 conformity and documented permeability reduction, may prefer Conplast X421IC as the direct equivalent to Sika-1.
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