Polyurethane is made up of two components, base and reactor. Polyol acts as the base, while isocyanide is the reactor component. The combination of both these in a specific design ratio creates a liquid coating for waterproofing applications. Polyurethane is a rather popular choice due to its ease of installation. Unlike other waterproofing systems like sheet membranes and liquid applied membranes, this polyurethane application requires comparatively less skill and supervision. Application is fast and this type of treatment can be used for post construction applications aswell.
Detailed methods for surface preparation and application are prescribed by the product supplier and often supervised by them in large project applications. Waterproofing is an expensive business, still it is better to prevent leakages and take all precautions during construction stage itself.
Polyurethane waterproofing procedure
- The roof surface is thoroughly cleaned and is made free of any foreign matter
- Any cracks on the surface preparation bed is cut to V section, cleaned and filled with a 1 part polyurethane based crack filling compound and 2 part white cement (1:2)
- The surface must be neutralized by removing alkalinity through the means of acid application
- A two pack polyurethane primer coat is first applied to the surface to serve as an adhesion coat. It is allowed to dry for at least 8 hours.
- Three successive finishing coats are then brush-applied, each with 2 component polyurethane mixed as per design ratio. Each coat is allowed to dry for at least 12 hours before applying the next.
- The PU coating is continued 150 mm up the parapets or walls. It should also be continued at least 100 mm into the rainwater pipes
- The final Polyurethane coat is sprinkled with a layer of 300 micron of sand

Where uses polyurethane waterproofing
- Roofs
- Balconies & Terraces
- Wet Areas
- Water Tanks / Ponds
- Pedestrian Decks
- Parking Decks / Bridges
- Detail Waterproofing
- Decorative Waterproofing
- Polyurethane Foamed Roofs
Advantages of polyurethane waterproofing
- Simple Application
- Forms Seamless Membrane without Joints or Leak Risk Areas
- Water Resistant
- Crack-Bridging up to 2mm, even at -10oo C
- Maintenance of Mechanical Properties at a Temperature Range of -30o C to +90o C
- Water Vapor Permeable
- Full Surface Adhesion
- Sun Reflectivity, Conducive to Thermo Insulation
- Anti-Root Properties
- Waterproofed Surfaces Usable for Medium to Heavy Pedestrian Traffic, Dependent on Mariseal System Top Coat
- Resistant to Detergents, Oils, and Common Chemicals
- Easy Local Repair, in Case Membrane is Mechanically Damaged
- Economical

