Below-Ground Waterproofing

About this course.

Below-ground waterproofing is the system that keeps water out of the parts of a building that are surrounded by earth — basements, cellars, lift pits, tanks, and the retaining walls that hold back soil — and it is a distinct and more difficult discipline than above-ground waterproofing because the water is not just landing on the structure and running off, but pressing against it continuously from all sides. The defining feature of below-ground work is that the barrier must resist water under pressure, permanently, from the outside, in a location that usually cannot be reached again once the building is finished. That combination — constant pressure and near-impossible access for repair — is why below-ground waterproofing must be designed and built to be right the first time, and why getting it wrong is among the most costly and disruptive failures in construction.

The structures involved include basements (habitable or storage space below ground, in homes and increasingly in apartments and commercial buildings), lift pits and plant pits (deep, small structures that sit in the water table), retaining walls (which hold back soil and, behind them, often hold back water too), and tanked structures (where a continuous waterproof "tank" is formed around the below-ground space). What they share is that soil, and the water in it, bears on them, and any water that gets past the barrier enters space that people use or that houses valuable equipment.