About Fosroc Nitocote CM662

Fosroc Nitocote CM662 is a flexible, two-component cementitious waterproof coating engineered for structures that must stay dry under hydrostatic pressure while remaining safe for human contact with water. It is the white-pigmented member of the Nitocote CM660/CM662 pair: CM660 is supplied grey, CM662 white, with the white shade allowing the coating to double as a clean, uniform finish layer rather than a hidden membrane. The product arrives as a pre-weighed kit — a cement-and-aggregate powder component combined with a synthetic polymer liquid — so that on site you only add the two parts together, with no separate water gauging or guesswork on the polymer dose. Once mixed and applied, the polymer cross-links through the cement matrix to give a coating that is far more elastic than plain cement render, capable of accommodating the small movements and shrinkage cracks that normally let water through rigid coatings. For Indian contractors, consultants and procurement teams, CM662 sits in the same decision space as established brush-applied cementitious systems and is specified wherever a tank, basement or roof needs a tough, breathable, potable-grade waterproofing skin that can be applied by general site labour with simple tools. Because it bonds tenaciously to sound concrete and masonry and tolerates both positive (water-side) and negative (back-pressure) application, it is a practical choice for both new construction and the rehabilitation of leaking existing structures where access to the water-bearing face is limited.

The technical insight

The performance of Nitocote CM662 comes from a polymer-modified cementitious chemistry: a Portland-cement-based powder graded to 0–0.3 mm is reacted with a synthetic polymer dispersion at a fixed liquid-to-powder ratio of 0.39 (9 kg liquid to 23 kg powder), producing a fresh mix of about 1.77 kg/litre. The polymer does two jobs — it dramatically improves adhesion (concrete bond of around 1 N/mm2, with failure occurring within the coating rather than at the interface) and it imparts elasticity so the cured film can bridge cracks up to 0.8 mm wide that develop after cure, provided a continuous 2 mm build is achieved. The cured coating resists positive water pressure of 7 bar (equivalent to a 70 m head) and negative pressure of 3 bar (30 m head), which is why it suits deep tanks, basements and lift pits subject to back-pressure from the soil side. It is also vapour-permeable — a water-vapour diffusion resistance coefficient of roughly 4800 (at 50–95% RH) means the structure can still breathe, avoiding the blistering that traps moisture under impermeable barriers. Applied at a minimum of two coats of about 0.7 mm each to reach the target 2.5 kg/m2, with roughly 6 hours between coats, it develops a pot life of about 1 hour and reaches full service performance in 5–7 days. Substrate temperature must be at least 8°C and the surface saturated-surface-dry (damp, not wet) at the time of application.

Where it is used

• Internal lining of potable-water tanks, overhead and underground reservoirs and sumps
• Waterproofing of basements, raft slabs, retaining walls and lift pits, including negative-side application
• Terraces, balconies, flat roofs and chajjas exposed to ponding and rain
• Swimming-pool shells and water features
• Bathrooms, kitchens, utility areas and other internal wet areas before tiling
• Sewage and effluent tanks, treatment-plant structures and water-channels
• Rehabilitation and re-waterproofing of leaking or aged concrete and masonry structures
• Protective skin over repaired concrete to seal fine shrinkage cracks

Key advantages

• Certified safe for contact with potable (drinking) water
• Resists both positive (7 bar / 70 m head) and negative (3 bar / 30 m head) water pressure, enabling back-side application
• Flexible film bridges shrinkage cracks up to 0.8 mm at a 2 mm build
• Excellent adhesion to concrete and masonry (~1 N/mm2, cohesive failure in the coating)
• No separate primer required, reducing steps and labour on site
• Vapour-permeable (diffusion resistance ~4800), so the substrate can breathe and avoid blistering
• Uniform white finish can serve as the visible final coat, unlike black bituminous membranes
• Pre-batched two-component kit removes site dosing errors
• Brush- or roller-applied with simple tools by general site labour, suiting Indian site conditions

Limitations & considerations

• Not a structural crack-bridging system — accommodates only fine cracks (up to 0.8 mm) that form after cure, not active wide or moving joints
• Requires a sound, clean, saturated-surface-dry substrate; defective or contaminated concrete must be repaired first with a suitable Fosroc Renderoc / Nitomortar repair mortar
• Substrate temperature must be at least 8°C, which can constrain winter or early-morning application in North India
• Cementitious film is less abrasion- and chemical-resistant than epoxy systems; aggressive chemical immersion calls for an epoxy coating such as Nitocote EP410 instead
• Short pot life of about 1 hour means only workable quantities should be mixed at a time
• Full service performance is reached in 5–7 days, so structures should not be put into water service prematurely
• Two coats with the correct interval and build are essential — under-application compromises pressure resistance and crack-bridging

Selection & best practice

Specifications

Industry use cases

How we position Fosroc Nitocote CM662

Within the Fosroc range, Nitocote CM662 is the white, flexible cementitious waterproofer for potable-water and general structural waterproofing; it sits alongside the grey CM660 and the closely related, widely specified Nitocote CM210 flexible cementitious coating. Where a job demands chemical or abrasion resistance beyond what a cementitious film offers — for example aggressive effluent or solvent exposure — the epoxy-based Nitocote EP410 is the more appropriate Fosroc protective coating, and substrate defects should be made good first with Fosroc repair mortars such as the Renderoc or Nitomortar ranges. Against the wider Indian market, CM662 competes directly with two-component flexible cementitious systems such as Sika’s SikaTop Seal / Sikalastic crystalline-and-cementitious coatings, Dr. Fixit Pidicrete / Roofseal Flex from Pidilite, MYK Laticrete (MBS-segment) cementitious waterproofing, and STP (Sika-owned) elastomeric coatings. CM662’s particular strengths in that field are its certified potable-water suitability, genuine resistance to both positive and negative water pressure, and a clean white finish that can remain visible. Specifiers should choose on verified head pressures, potable certification, crack-bridging width and breathability rather than brand alone, and Space Arc Engineering, as an authorised Fosroc distributor and applicator across Delhi NCR and Pan-India, can advise on the correct Nitocote grade and supply both the material and trained application for the structure in question.

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