8 Steps Guide: How to Waterproof a Concrete Foundation?

Written By Adam Paul - Waterproofing Expert

Concrete foundation waterproofing is important to protect foundation from the water damage. When answering the question How to waterproof concrete foundation? Is interesting. We have done this several times in our projects and we wish to bring you the best information with best practice from Aqviz experience. So you should follow the below 8 step by step guide to waterproof concrete foundation from starting to finishing.

8 Steps to Waterproof a Concrete Foundation

You should follow these 8 steps to waterproof a concrete foundation

Inspect the foundation for waterproofing.
Choose a foundation waterproofing membrane
Prepare foundation surface and apply primer
Install foundation waterproofing membrane
Seal waterproofing joints and penetrations
Install foundation drainage system
Protect the foundation waterproofing layer
Maintain the foundation waterproofing

1. Inspect the Foundation for Waterproofing

Before we begin foundation waterproofing, we need to assess the foundation for signs of water damage. You should look for foundation cracks, efflorescence (white, powdery residue), mold, or damp spots. Because they occur due to moisture intrusion. A musty odor in the basement or peeling paint on foundation walls are strong signs of water damage in the foundation.

At Aqviz, we always recommend a thorough inspection before applying any waterproofing solution. It helps to identify and address these issues early and ensures the waterproofing system performs effectively, preventing costly repairs down the line.

2. Choose a Foundation Waterproofing Membrane

Selecting the right foundation waterproofing membrane depends on whether we’re working on the interior or exterior of the foundation. Exterior membranes are ideal for preventing water infiltration from outside. They are typically made of sheet or liquid-applied membranes that form a seamless barrier on the foundation surface. These require proper drainage, such as a perforated drainpipe and gravel backfill, to channel water away from the foundation.

Interior foundation wateproofing membranes help to manage moisture that has already penetrated to the foundation. You should use French drains, vapor barriers, sump pumps, and dehumidifiers for interior waterproofing.

At Aqviz, we recommend exterior waterproofing whenever possible for long-term foundation protection.

3. Prepare the Foundation Surface and Applying Primer

Proper foundation surface preparation is crucial for membrane adhesion. First, we clean the foundation wall using a wire brush, pressure washer, or grinder to remove dirt, debris, and loose material. If cracks are present, we seal them using polyurethane or epoxy crack injection polyurethane for flexible, active cracks and epoxy for structural repairs. Larger voids or deteriorated areas on the foundation surface should be patched with hydraulic cement.

Once foundation repairs are done, we apply a primer (if required by the membrane manufacturer) using a roller or sprayer. This step enhances adhesion and ensures a strong bond between the membrane and the foundation. At Aqviz, we emphasize meticulous surface prep to prevent future failures in the waterproofing system.

4. Install Foundation Waterproofing Membrane

Once the foundation surface is prepped, we apply the waterproofing membrane using the appropriate method.

Liquid applied membranes are either sprayed, rolled, or troweled onto the foundation wall. It creates a seamless, flexible barrier that adapts to minor cracks and movements on the foundation surface.
Sheet membranes, typically self-adhering or torch-applied, provide consistent thickness and excellent durability but require precise overlapping and sealing at seams.

Aqviz, we highly recommend you to use liquid membranes for their ease of application on foundation complex surfaces and sheet membranes for high-durability requirements.

5. Seal Waterproofing Joints and Penetrations

Sealing joints, seams, and penetrations is critical to preventing further leaks from the foundation surface. You should seal the areas such as wall-to-footing joints, pipe penetrations, and membrane overlaps using additional waterproofing membranes.

For pipe penetrations, we use flexible rubberized sealants or prefabricated boots to ensure a watertight fit, allowing for slight movement without breaking the seal. If you do not seal any seam or gap can become a weak point on the foundation surface. It may lead to water intrusion inside over time.

6. Install the Foundation Drainage System

A proper drainage system is essential to reduce hydrostatic pressure and prevent water buildup against the foundation. Exterior drainage systems, like perforated drainpipes (French drains) wrapped in gravel, are installed at the footing level to direct water away from the foundation. These work best when combined with waterproof membranes for full protection.

Interior drainage systems, such as basement drain tiles and sump pumps, are ideal for managing water that has already infiltrated, especially in retrofitting projects. At Aqviz, we recommend exterior drainage whenever possible for proactive waterproofing, but interior systems are effective backups for wet basements.

7. Protect Foundation Waterproofing Layer

To prevent damage to the waterproofing membrane during backfilling or from external forces, our experts use,

Drainage boards to protect membranes and improve water flow.
Protection boards to shield against impact damage.
Geotextile fabric to prevent soil from clogging drainage pipes.
Gravel backfill to reduce soil pressure and improve drainage.
Plywood sheeting for temporary protection during construction.

8. Maintain Foundation Waterproofing

Regular maintenance ensures long-term waterproofing effectiveness in the foundation surface. These are the key steps to maintaining foundation waterproofing.

Inspect for foundation cracks or membrane damage annually.
Ensure foundation drainage pipes remain clear of debris to prevent clogging.
Check sump pumps (for interior systems) and test their functionality.
Monitor soil grading to maintain proper water runoff away from the foundation.
Reapply sealants or coatings if signs of wear appear.

What are the Reasons for Foundation Water Leaking?

These are the 6 reasons for foundation water leaking.

Inadequate or clogged drainage systems allow water to accumulate around the foundation.
Excess groundwater buildup increases pressure, forcing water through cracks and weak points.
Foundation structural shifts, settling, or aging cause cracks that let water seep in
Water pools instead of draining away due to improper soil grading
Water overflows and saturates the soil around the foundation
Certain soils retain moisture, swelling and contracting, which stresses the foundation

What is Negative Side Foundation Waterproofing?

Negative side foundation waterproofing is the process of applying waterproofing materials to the interior (negative) side of a foundation wall to stop water penetration from the outside. It is used when exterior (positive-side) waterproofing is not possible, such as in existing buildings or confined spaces.

What is Positive Side Foundation Waterproofing?

Positive side foundation waterproofing is the process of applying waterproofing materials to the Exterior (positive) side of a foundation wall to stop water penetration to the inside. It is used mostly on new foundation and newly constructured foundations.

Is the positive side and negative side the same as interior and exterior foundation waterproofing?

Yes, they both are the same. Positive side waterproofing is similar to exterior foundation waterproofing while negative side is similar to interior foundation waterproofing.

Read more about: Interior vs Exterior Foundation Waterproofing

What should Consider before Choosing a Foundation Waterproofing Membrane?

You should consider these factors when choosing a foundation waterproofing membrane.

Water resistance of the membrane
Flexibility resistance of the membrane
Adhesion resistance of the membrane
Chemical resistance of the membrane
Root resistance of the membrane
The workmanship of the membrane