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 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.