TERRACE & PODIUM WATERPROOFING

Podium/Terrace Area-Waterproofing of any podium or terrace area in general is very complex as it is exposed to variable weather conditions, foot traffic etc. It is often the leakage through the terrace that causes severe dampness in the ceilings, thus spoiling the look of expensive interiors and leading to weakening of the roof slab and concrete. Critical parameters impacting selection of the material is based on the following: –

1. Surface has an existing sound slope without any hollowness or water logging issues, then a top coat system is used.
2. In case of treatment over the mother slab, undercoat system is used followed by slope screed.

But in case if the existing slope shows sign of water logging or extreme hollowness, the slope screed is removed to expose the mother slab and an undercoat system is performed followed by screed.

Based on if it is an under coat or a top coat, the solutions are of various types.

Under Coat System- These are systems which are directly applied on to the mother slab hence giving the system superior durability. These systems can be classified into 2 major types-

1) Polyurethane coating system– There are 2 types

a) Pitch modified PU –Pitch is a resin such as bitumen, coal tar etc. which when combined with PU forms such a system. These systems are used as an under coat in case of large span areas, they have high elongation and are very tough.

b) Pure PU

Prior to application of these systems, the surface must be clean and sound as per checklist i.e., all joints, honeycombs and hollowness must be packed with PMM (Polymer Modified Mortar) /Non-Shrink repair mortar. Angle fillet min 50*50mm must be made all along the corners using PMM. Bore packing must be done using non shrink grout like GP2. Surface must be completely dry.         

If in case concrete is not fully dry a water based epoxy primer can be used.

Cracks, voids etc. should be repaired using PU Sealant post application of primer only.

2) Polymer based Elastomeric Cementitious coating system- Polymer based Elastomeric Cementitious coating systems are high performance elastomeric cementitious coating used for waterproofing and to protect atmospherically exposed reinforced concrete structures from attack by acid gases, chloride ions, oxygen & water.

These systems can be used on concrete, brick and block work substrates and is equally suitable for new and existing structures. The product is designed to reface and even out variations in concrete and masonry surfaces and bridge shrinkage cracks. It provides a seamless, flexible waterproof coating suitable for water tanks, reservoirs, drainage culverts basements and roofs. These products provide a tough durable water-resistant coating. These systems are preferred as an undercoat system as they are not UV stable.

Prior to application of these systems, the surface must be clean and sound as per checklist i.e., all joints, honeycombs and hollowness must be packed with PMM (Polymer Modified Mortar) /Non-Shrink repair mortar. In case if the Angle fillet is not present, min 50*50mm must be made all along the corners using PMM. Bore packing must be done using non shrink grout like GP2. Surface must be in SSD state.    

 Also depending on the porosity of the concrete, a silicon-based sealer Zycosil or an acrylic based sealer La Brush seal can be provided as an additional coating before application of the cementitious waterproofing system.

Top coat systems-These coatings are UV Stable and can be exposed to light/mild foot traffic. In some cases, they are also used as a heat reflective coat depending on the color and SRI Value. It is further divided depending on the base material used.

1) Acrylic Polymer based systems- Single component acrylic coating systems form a part of this category, these coating are elastomeric, flexible, tough and can be left exposed. Also, they can be subjected to light foot traffic. Surface must be in SSD state before application of primer. Recommended for areas under 2500 sq ft.

2) PU Hybrid-These systems are a combination of PU and acrylic compounds to form a tough coating. Surface must be in SSD state. Recommended for areas ranging between 2500-5000 sq ft .

3) Pure Polyurethane coating system-a pure PU based system can be of single/two component. These systems have high elongation and can be used for large span of area. Recommended for areas over 5000 sq ft.

Prior to application of these systems, the surface must be clean and sound as per checklist i.e., all joints, honeycombs and hollowness must be packed with PMM (Polymer Modified Mortar) /Non-Shrink repair mortar. Pressure grouting using PRAN (Permeability Reducing Admix for Non-Hydrostatic Conditions) at all weak spots/zones. In case if the Angle fillet is not present, min 50*50mm must be made between the base slab and wall using PMM. If a solvent based system is being used, substrate must be completely dry.