Sika RainTite I
A site-gauged acrylic polymer emulsion that turns ordinary cement slurry into a bonded, waterproof coating for roofs, tanks, basements and sunken slabs.
What is it?
A multifunctional acrylic copolymer emulsion that is blended with cement (and sometimes sand) on site to make waterproof coatings, bonding slurries, polymer mortars and paint admixtures.
Where is it used?
Roof slabs, terraces, sunken slabs, basements, water tanks and sunshades, plus repair, plastering and grouting work across Delhi NCR and pan-India projects.
Why use it?
It converts a low-cost cement slurry into a flexible, low-permeability, well-bonded coat, cutting rain penetration and improving abrasion and salt resistance without a proprietary membrane.
How is it applied?
Gauge with water, mix into cement at 1:2, then brush two crosswise coats onto a saturated-surface-dry substrate, curing 3-5 days before ponding.
About Sika RainTite I
Sika RainTite I sits in a category that Indian site teams know well but often misunderstand: it is not a bucket you open and roll on, but an acrylic polymer emulsion that you gauge with water and mix into ordinary cement to build the waterproof coat yourself. The polymer is an acrylic copolymer with special additives, supplied as a milky-white liquid at roughly 28% solids. Once it is stirred into a cement slurry and brushed on, the acrylic film knits the cement matrix together, filling capillary pores and giving the hardened layer flexibility and grip that a plain cement wash could never hold. That is why the same tin can serve so many jobs on one site, from a terrace coating to a bonding slurry under a repair mortar.
For contractors, the appeal is control and economy. Because you supply the cement, the coating cost per square metre is low, and the ratios can be tuned for the task in hand, thinner as a paint additive, richer as a brush topping loaded with silica sand. The trade-off is that performance depends on getting those ratios and the surface prep right, so RainTite I rewards a disciplined crew. Space Arc supplies it in the full Sika India pack range with technical back-up so that specifiers and applicators can match the grade, dosage and system detailing to the structure rather than guessing on site.
The technical insight
The mechanism is polymer-modification of a cement matrix. Ordinary hydrated cement is riddled with interconnected capillary pores that let water track through; a plain cement slurry seals almost nothing. When RainTite I is gauged and mixed in, the acrylic copolymer particles coalesce as the mix loses water and cure, forming a continuous polymer film that bridges those pores and lines the cement paste. The result is a composite coat that is far less permeable, more flexible and better bonded than the cement alone, with a tensile adhesion strength around 0.5 N/mm2 as a bonding slurry. Crucially, RainTite I is never brushed on neat as a bonding agent, cement and sand must always be added, because it is the cement it modifies, not a standalone membrane. The two crosswise coats, applied onto a pre-wetted dark-matt substrate, then curing for three to five days, are what let the polymer film develop fully before any water load.
Where it is used
- Waterproofing coating for roof slabs, terraces and sunshades, applied as a RainTite I : cement 1:2 brush coat
- External and internal waterproofing of RCC water tanks, retaining walls and basements
- Waterproof brush topping for sunken slabs of bathrooms, balconies and utility areas
- Bonding slurry between old and new concrete before repair mortars, plaster or screeds
- Polymer-modified repair and plaster mortars needing higher strength and lower permeability
- Additive to cement-based paints to improve impermeability, water repellence and anti-fungal performance
- Treatment against leaching, efflorescence and saltpetre (saltpetre) action on masonry
- Admixture for injection and repair grouts where extra cohesion and bond are required
Key advantages
- Highly economical because the applicator supplies the cement, keeping cost per square metre low
- One product covers many uses: coating, bonding slurry, mortar admixture and paint additive
- Markedly reduces permeability and rain penetration by lining the cement’s capillary pores
- Bonds well to most sound cementitious and masonry substrates
- Improves flexural strength, abrasion resistance and durability of the modified mortar or coat
- Improves resistance to salt permeation, leaching and fungal growth
- Water-based, low-odour and non-flammable, suited to occupied buildings and confined tanks
- Long 18-month shelf life and a wide 250 g to 200 kg pack range for jobs of any size
Limitations & considerations
- It is not a ready-to-use membrane; every application depends on correct on-site mixing with cement (and sand)
- Field-batched ratios mean performance varies with the crew’s discipline, unlike a factory-dosed two-part system
- Must never be used neat as a bonding agent; cement and sand have to be added or bond will fail
- Not a heavy-duty, high-build elastomeric membrane for structurally cracking or heavily trafficked decks
- Requires thorough substrate prep (min 1.0 N/mm2 pull-off, laitance and contaminants removed) and disciplined curing
- Ratios and consumption need adjustment when using PPC or blended cements instead of OPC
Selection & best practice
Prepare the substrate to a minimum 1.0 N/mm2 pull-off, mechanically removing laitance, curing compounds and loose material, and profile all horizontal-to-vertical junctions with a 25 mm x 25 mm mortar fillet. Pre-wet the surface for about two hours so it reads dark-matt with no free water or shine before you coat. Gauge RainTite I with water, then stir the cement into the gauging solution (not the reverse) with a slow drill to a lump-free mix, and use it within 20-30 minutes at 30 C. Brush the first RainTite I : cement 1:2 coat in one direction, let it harden for two to six hours, then apply the second coat crosswise; where extra strength is needed, embed Sika Fabric-50 into the fresh base coat. Work between +10 C and +40 C, cure for a minimum of three to five days under polyethylene, wet hessian or a curing compound such as Sika Antisol, and do not pond water before five days. Protect exposed roof coatings with a screed or separation layer for longer service life.
Specifications
| Product type | Multifunctional acrylic polymer emulsion (mixed with cement on site) |
| Chemical base | Acrylic copolymer and special additives |
| Appearance / colour | Liquid / milky white |
| Density | ~1.03 kg/L at +27 C |
| Solid content by weight | ~28% |
| Tensile adhesion strength | ~0.5 N/mm2 (as bonding slurry) |
| Waterproof coating mix / consumption | RainTite I : Cement = 1:2; ~200 g/m2 of RainTite I per coat (mixture ~500 g/m2 per coat), min 2 coats |
| Pack sizes | 250 g, 500 g, 1, 5, 10, 20, 50 and 200 kg containers |
| Shelf life / storage | 18 months; store dry between +5 C and +35 C, protect from frost and direct sunlight |
Industry use cases
Residential & housing
Terrace, sunshade and sunken-slab waterproofing for independent homes and apartment blocks, where an economical brush-applied coat over an RCC slab suits repeated small pours.
Water retaining structures
Internal and external coating of RCC water tanks, sumps and retaining walls, using the polymer-modified slurry to cut seepage and resist leaching.
Commercial & institutional buildings
Bathroom and wet-area sunken slabs, basement walls and plaster in offices, schools and hospitals where low odour and water-based chemistry help in occupied spaces.
Repair & rehabilitation
Bonding slurry and polymer-modified mortars for patch repairs, re-plastering and treating efflorescence or saltpetre action on older masonry.
Paint & finishing works
Added to cement-based paints on light shades to raise impermeability, water repellence and anti-fungal performance on external walls.
Frequently asked questions
Is Sika RainTite I a ready-to-use waterproofing membrane?
What is the mixing ratio and coverage for a roof waterproofing coat?
Can I brush RainTite I directly onto concrete as a bonding agent?
How long before I can fill a tank or pond water on a treated roof?
Does it work with PPC or only OPC?
What pack sizes does Space Arc supply and how should it be stored?
How we position Sika RainTite I
Sika RainTite I is the value-engineered, site-gauged choice within Sika’s waterproofing range: economical and versatile, but reliant on the crew mixing it correctly with cement. Where a project wants factory-controlled dosing and a thicker, more crack-accommodating film, step up to a two-component acrylic-cement system such as Fosroc Brushbond RFX, or Sika’s own elastomeric membranes, and pair it with Sika Fabric-50 for reinforcement at junctions and Sika Antisol for curing. For deep or hydrostatic basements and structural cracks, treat RainTite I as a coating layer within a wider system rather than the sole barrier, and combine it with crystalline or injection solutions from the same catalogue. Our team can specify the right grade, sister products and detailing for the structure.
Fosroc Brushbond RFX — Choose Brushbond RFX when a specifier wants a factory-batched two-component acrylic-cement coating with controlled polymer dosing and a more flexible, crack-bridging film, rather than a field-mixed emulsion whose ratio depends on the applicator.
Related Waterproofing products
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