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Below Grade Waterproofing & Drainage

Updated: Sep 14, 2020

In most areas, building codes require at least a damp proofing coating for below grade structures, however, a more durable waterproofing coating is typically not much more in cost and provides greater protection. Depending on the water table of the construction site and the potential of water under pressure (hydrostatic pressure) code may require a waterproofing system with an adequate drainage system to move water away from the foundation.

The first and perhaps most important line of defense against water intrusion is a proper drainage system to divert water from foundation walls and the foot of the foundation. Whether it is simply just aggregate allowing water to drain down instead of being forced into foundation walls or a more elaborate drainage system, diverting water away from a structure is an integral part of most waterproofing solutions.

A properly drained foundation will greatly reduce hydrostatic pressure allowing water a place to go rather than being pressed into your foundation walls. As aggregate can get clogged with dirt, a more modern solution is to apply a dimpled drainage board to the foundation walls after the walls themselves have been waterproofed with a sheet membrane or a coating. The dimples in this drainage board allow space between the earth and the structure where water can flow to a drain at the foot of the foundation.

Filter fabrics are typically used over the drainage board to keep dirt and sediment from blocking the drainage channels. As the hydrostatic pressure is interrupted by the empty space created by the drainage board, the water travels downward to a drainage system at the foot of the foundation which carries the water away to a sump system, municipal drain or elsewhere away from the structure.

While an effective waterproofing system requires added construction time and cost to the project the return in a dry and stable structure certainly beats having to excavate and install a waterproofing system down the road after construction is complete and the building is occupied. IWS offers “Innovative Waterproofing Solutions” that are durable and environmentally kind for building owners and safe and easy to apply for contractors and waterproofing application professionals. Our products have undergone rigorous testing with impressive results through ASTM and are Miami Dade approved. Data sheets and contractor specifications available upon request. ­


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