Frequently Asked Questions

How many coats of Nitoproof 300 should be applied to a below-ground basement wall and what is the drying time between coats?

A minimum of two coats of Nitoproof 300 should be applied to all below-ground concrete surfaces to ensure a continuous, pinhole-free bituminous coating. A single coat of brush-applied bituminous emulsion on a rough formed-concrete surface may have pinholes or thin areas at aggregate protrusions and surface irregularities — the second coat applied in a crossing direction fills the pinholes in the first coat and builds the total film thickness to 1.0 to 1.5 mm dry film, which provides the required waterproofing and chemical resistance. The first coat must dry to a tack-free, firm condition before the second coat is applied — at 25 degrees Celsius and normal humidity, the first coat of Nitoproof 300 dries to tack-free within 2 to 4 hours. In Indian summer (35 degrees Celsius, low humidity), the first coat may be dry within 1 to 2 hours. In monsoon conditions (high humidity, cooler temperatures), allow 4 to 6 hours between coats. The full two-coat system should cure for a minimum of 24 hours at 25 degrees Celsius before the structure is backfilled — backfilling against an incompletely cured bituminous coating can damage the coating surface. For below-ground structures subject to high hydrostatic pressure (water table permanently above the base of the structure), a three-coat application of Nitoproof 300 or an upgrade to a higher-performance system (Proofex Engage pre-applied membrane or Proofex 10 sheet membrane) should be specified.

Can Nitoproof 300 be applied to a wet concrete surface immediately after formwork is struck in monsoon conditions?

Nitoproof 300, as a water-based bituminous emulsion, can tolerate application to a damp concrete surface to a greater degree than a solvent-based coating or an epoxy product — it does not require a bone-dry substrate and can be applied to concrete that has been de-shuttered in monsoon conditions where the surface is slightly damp from absorbed moisture. However, there is a difference between surface-damp concrete (the pores are saturated but no free water is visible on the surface) and wet concrete with free water running on the surface or pooled water in surface depressions. Nitoproof 300 should not be applied to a concrete surface with free running water or standing pools — the water dilutes the emulsion at the surface and prevents the bituminous film from forming correctly on the substrate. Surface preparation to remove any free water (brushing or blowing off surface water, allowing 30 to 60 minutes after rainfall for the immediate surface moisture to dry) before Nitoproof 300 application is sufficient in monsoon conditions. The concrete temperature must be above 5 degrees Celsius (which is never a constraint in Indian construction), and ambient temperature should be above 10 degrees Celsius — again, not a constraint in India at any time of year. Application directly after de-shuttering on a damp surface in monsoon conditions is standard site practice for Nitoproof 300 in Indian basement construction.

Is Nitoproof 300 sufficient waterproofing for a below-ground basement in Delhi where the water table is expected to be 1 to 2 metres above the basement floor?

For basements in Delhi where the seasonal water table (during July to September monsoon) rises to 1 to 2 metres above the basement floor level, Nitoproof 300 alone as the waterproofing system may not provide sufficient hydrostatic resistance for a waterproof basement. The hydrostatic pressure of 1 to 2 metres of water head (10 to 20 kPa at the base of the water column) is a real pressure loading on the coating, and a 1 to 1.5 mm bituminous emulsion coating is rated for only modest hydrostatic resistance — it provides good protection against soil moisture and damp ground conditions but is not a high-head waterproof membrane. For Delhi basements with a seasonal water table above the basement floor level, the appropriate waterproofing system is either: a sheet membrane system (Proofex 10 or Proofex Engage) that is rated for the design hydrostatic head; a combination of Nitoproof 300 as a base protection coat plus Brushbond TG or Nitoproof 600 cementitious slurry coating for improved waterproofing; or an integral crystalline admixture system (Proofex Integral) in the concrete combined with a surface-applied Nitoproof 300 protection coat. The exact system should be designed by a waterproofing engineer based on the site investigation report (borehole data, seasonal water table levels, soil permeability) and the required internal waterproofing grade for the basement use. Space Arc Engineering can provide a system recommendation based on project-specific information.