Waterproofing concrete is essential at below-grade areas to prevent water intrusion and structural damage.
In many areas of the world we have exhausted the building sites having the good drainage pattern inherent in previously abundantly available high-ground topography. Through this attrition, we are finding the only convenient and available sites are located in low-lying areas in or near swamps, flood plains, along rivers and lakes, etc. These areas, with higher water tables and their concomitant water pressures are also presenting us with possibilities of even higher water heads as nearby development proceeds. We have, in addition, the rising water levels already being experienced in many of the lakes and rivers. Many of these sites have the additional problems of contaminants known to adversely affect many types of concrete and concrete masonry units.
Waterproofing is required at below-grade concrete surfaces for several reasons. The primary reason is to keep moisture from intruding into the facility. However, it is also required to protect the structural contents from water infiltration that can cause structural damage to the concrete or corrosion to the imbedded steel. Concrete is by design a porous material, and water can pass through it by hydrostatic pressure, water vapor gradient or capillary action. Water can also enter at cracks, structural defects or at improperly designed or installed joints. Waterproofing is also required to eliminate deterioration to the concrete that can occur from exterior and interior chemicals that are present at the building site.