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Below Grade Waterproofing Tips & Tricks

Steve Thompson
September 2, 2022

There are various waterproofing solutions on the market, but choosing the right method for the right project is important. Choosing appropriate waterproofing products and a team of seasoned experts is crucial for successful results. Here are helpful below-grade waterproofing tips & tricks to protect your home or commercial building from water damage.

Definition of Below Grade Waterproofing

"Below grade" means below ground level. Regarding below-grade waterproofing treatment below ground level of a structure or building, it's crucial to hire an engineer to conduct testing for a geotechnical report. It's important to study the soil for harmful chemicals that can weaken waterproofing efforts. The goal of below-grade waterproofing is to prevent underground water from coming into contact with the building’s foundational structure. It includes waterproofing your basement and other below-grade areas.

The factors that affect the type of waterproofing solution you select should be based on the building, climate conditions, drainage system, and soil quality. Water is under pressure below the ground and tries to force its way through cracks in the foundation. The waterproofing membrane, which is a thin protective layer of coating to resist water penetration, must be strong enough to withstand this pressure.

The three main types of waterproofing solutions to consider are:

1. Positive side - This ideal solution is applied to the building's exterior and requires access to the outside face of the structure. It involves installing a membrane between the substrate and water or moisture.

2. Negative side - An alternative solution is to apply waterproofing to just inner surfaces, but the structure can still eventually crack, so it's not the best choice for durability.

3. Blind side - When property lines or space limitations are issues, this coating option is applied to the underside of structural slabs.

Exploring Below Grade Waterproofing Solutions

Before deciding on a below-grade waterproofing solution, you'll need to assess whether water or moisture is causing damage to your structure and if the solution calls for damp proofing or waterproofing.

Water dissolves in wood and facilitates the growth of microorganisms and contaminants harmful to human respiratory organs. If the combination of fungus and mold spreads, it can cause health problems and structural degradation. Neglect and poor maintenance of home or commercial building conditions are often the main reasons outdoor decks must be replaced instead of salvaged.

Rising groundwater poses risks of damage to your structure, so you must check to see if the water table exceeds the waterproofing membrane level. If so, you'll need high-performance waterproofing in which the membrane connects to the structure with adhesive material. Mechanical bonding is not as protective against water.

Below-grade walls must be considered for below-grade waterproofing to avoid expensive repairs in the future. Hydrostatic pressure can build up, and the gravitational pull of water forces moisture into air pockets within the structure. This water pressure can severely crack the foundation, leading to subterranean parking and basement flooding. Part of the problem is if the concrete of a below-grade wall dries unevenly, it can form tiny air tubes that trap water. This condition can create capillary action in which water carries salts and minerals through the concrete that weaken the structure.

An effective solution for below-grade waterproofing is Polyguard, which withstands harsh conditions. It's also a reliable solution for lightweight drainage and is designed to minimize hydrostatic pressure. Polyguard proved resilient for Houston Country Club's underground garage construction in 2011.


Use these below-grade waterproofing tips & tricks to protect your home or commercial building from water damage. Contact West Coast Deck Waterproofing experts for more information on the best ways to deal with and prevent below-grade water leaks.