Foundation Crack Injection: What to Know About?

Written By Adam Paul - Waterproofing Expert

What is Foundation Crack Injection? Foundation crack injection is an efficient method to repair deep and wide cracks in concrete foundations. This technique involves injecting specialized materials directly into the cracks, filling voids, and creating a watertight seal. It can be used to stop live leaking and it helps to prevent water infiltration and structural damage. 

We recommend foundation crack injection as an effective and long-lasting solution for basement walls, crawl spaces, and other concrete structures prone to cracking. When you do this properly it provides a durable protection for the foundation surface. It is an additional protection to the foundation surface rather than just covering it using a foundation waterproofing membrane. 

Aqviz waterproofing experts share their knowledge with you in this guide. As well as we have included all the recommendations and our method statements. So we highly recommend you to refer to this guide before starting your foundation crack injection project. Let us know if you have any problems regarding this. 

What Are the Foundation Crack Injection Methods?

There are two primary methods used for foundation crack injection: epoxy injection and polyurethane (polyurethane foam) injection. Each method has its own advantages depending on the type of crack and the foundation’s condition.

1. Epoxy Injection: This method is best for structural repairs. Epoxy is a high-strength adhesive that bonds concrete together, restoring the foundation’s original strength. We typically use it for dry cracks where structural integrity is a concern.
2. Polyurethane Injection: Ideal for stopping water leaks, polyurethane expands when it comes into contact with moisture, creating a flexible and watertight seal. We often use this for active leaks in basement walls and foundations that need the flexibility to handle slight movements over time.

Choosing the right method depends on the crack’s severity, whether it’s actively leaking, and the foundation’s overall condition. In many cases, we recommend polyurethane is preferred for waterproofing, while epoxy crack injection is used for structural reinforcement.

What Is Used to Inject Foundation Cracks?

The success of foundation crack injection depends on using the right materials. At Aqviz, we rely on high-quality epoxy resins and polyurethane foams to ensure long lasting results.

1. Epoxy resin: Epoxy resin has high bonding strength. It is injected under pressure to weld concrete back together. When it dries it becomes an excellent water resistance and strong material. 
2. Polyurethane foam: Polyurethane foam expands upon injection and fill the cracks and seal the leaking water. Its flexibility allows the foundation to shift slightly without reopening the crack.

In addition to the injection materials, we use specialized equipment such as injection ports, applicator guns, and pressure pumps to ensure the material penetrates deeply into the crack. The right approach ensures the repair holds up against time, moisture, and foundation movement.

What Tools Are Needed for Foundation Crack Injection?

To achieve a successful foundation crack injection, you should use the right tools and select the correct materials. At Aqviz, we always ensure we have a complete set of professional grade equipment before starting the process.

Here’s a breakdown of essential tools:

1. Injection ports: These small nozzles are placed over the crack to allow the injection material to enter the foundation cracks without spilling.
2. Injection gun or pump: A high-pressure applicator is necessary to push the epoxy or polyurethane deep into the foundation cracks. For smaller cracks, a manual gun works well, while larger cracks may require a powered pump.
3. Surface sealant (Epoxy paste or hydraulic cement): Before injecting, we seal the surface of the crack with an epoxy paste or hydraulic cement to keep the material from leaking out.
4. Drill and wire brush: Used to prepare the foundation cracks by cleaning out debris and ensuring proper adhesion of the injection material.
5. Protective gears: Safety glasses, gloves, and respirators protect against fumes and skin contact with chemical resins.

We highly recommend using proper waterproofing tools. When you skip any of these can result in poor adhesion, incomplete penetration, or leaks in the repaired crack on the foundation.

What Is the Foundation Crack Width for the Injection Process?

Not all cracks are suitable for the foundation crack injection process. The crack width plays a critical role in determining whether injection is the right repair method.

1. Best crack size for injection: Typically, we inject cracks that range from 1/32 inch (0.8 mm) to 1/4 inch (6 mm) in width. When the crack becomes smaller, it does not allow proper material penetration, while wider cracks may require additional reinforcement.
2. Hairline cracks: If the crack is too narrow (less than 1/32 inch), it may be difficult to inject epoxy or polyurethane effectively. In such cases, we sometimes widen the crack slightly using a grinder before applying the injection material.
3. Large cracks (Over 1/4 inch): For wider cracks, additional techniques such as backer rods, multiple injection passes, or even a combination of epoxy and polyurethane might be necessary to ensure a complete seal.

What Is the Pressure for Foundation Crack Injection?

Applying the right injection pressure is essential for ensuring complete penetration of the crack without causing damage to the foundation. At Aqviz, we carefully adjust the pressure based on the crack’s width, depth, and material used.

1. Low pressure injection (20-100 psi): Low pressure injection is highly recommended for epoxy injections where slow penetration is required for strong bonding or used for small cracks.
2. Medium pressure injection (100-500 psi): Medium pressure injection is often used for polyurethane injections where flexibility and water-sealing properties are needed. Often used for polyurethane injections where flexibility and water-sealing properties are needed. This is highly recommended for active leaks.
3. High pressure injection (500+ psi): High pressure injection is highly recommended for the deep, wide cracks where material must travel a significant distance. 

You should always start at the lowest effective pressure and gradually increase as needed, ensuring complete coverage without causing additional stress on the foundation.

When Should You Conduct a Foundation Crack Injection?

Timing is everything when it comes to foundation crack injection. Conducting the process at the right moment ensures maximum effectiveness and longevity.

Epoxy injection works best on dry cracks, so we recommend waiting for a dry season or actively drying the area before applying. While polyurethane injection is ideal for actively leaking cracks and can be performed even when water is present.

However, the best time for crack injection is typically spring and fall, when temperatures are moderate and the foundation is less likely to expand or contract significantly. During winter, the concrete is too cold, which can affect adhesion. In summer, expansion due to heat may temporarily close cracks, leading to incomplete injection.

How Long Does It Take for Foundation Crack Injection?

Typically, foundation crack injection take 2 to 4 hours. But it depends on the crack size, type of injection material, and preparation needed.

1. Small cracks (under 5 feet): Usually take about 1 to 2 hours, including preparation and cleanup.
2. Larger cracks (5+ feet or multiple cracks): This can take 3 to 4 hours or more, depending on accessibility and the material used.
3. Complex cases: If the crack is deep, actively leaking, or requires multiple injection passes, it may extend the process by an hour or two.

How Long Does It Take to Cure Foundation Crack Injection?

The curing time of the foundation crack injection can depend on the type of crack injection. Normally epoxy takes 4 to 24 hours to cure fully and it will take 48 hours for the maximum bonding strength. Polyurethane crack injection can sealing 15 to 30 minutes, but full curing can take 24 to 72 hours, depending on moisture levels.

For the best results, we always recommend waiting at least 24 hours before applying any finishes, painting, or exposing the repaired area to heavy loads. In colder or humid conditions, curing times may be slightly longer.

When Should You Remove Foundation Crack Injection Ports?

Removing injection ports at the right time ensures a clean and professional finish without disrupting the seal inside the crack.

• Epoxy injection: We recommend waiting at least 24 hours before removing the ports to allow the epoxy to fully bond.
• Polyurethane injection: Ports can often be removed after 6 to 12 hours, but waiting 24 hours is ideal for ensuring the material has expanded and sealed properly.

Once cured, we remove the ports using pliers or a chisel, then smooth out the surface using a grinder or patching material for a clean look. If painting or finishing is planned, we recommend waiting an extra day or two to ensure the repair is completely set.

How Long Can a Foundation Crack Injection Last?

When properly applied, foundation crack injection is a permanent repair that can last 20+ years or even a lifetime. However, longevity depends on factors like:

Material quality: High-quality epoxy and polyurethane products provide the best durability.

Foundation movement: If the foundation continues to shift due to soil settlement or hydrostatic pressure, new cracks may form nearby.

Waterproofing conditions: A polyurethane injection is flexible and can withstand minor movement, while an epoxy injection is rigid and better for structural reinforcement.

At Aqviz, we’ve seen properly injected cracks remain sealed for decades, provided the foundation is well-maintained and free from excessive movement or drainage issues.

Are Foundation Crack Injections Eco-Friendly?

The environmental impact of foundation crack injection depends on the materials used and their long-term benefits. While traditional epoxies and polyurethanes are synthetic chemicals, many modern formulations are designed with low-VOC (volatile organic compound) emissions and minimal environmental impact.

How Much Does It Cost for Foundation Crack Injection?

The cost of foundation crack injection varies based on crack size, repair complexity, and materials used. On average, homeowners can expect to pay $300 to $800 per crack, with some larger or deeper foundation cracks costing more.

Here’s a breakdown of the key cost factors:

Crack Length:

• Small cracks (under 5 feet) – $300 to $500
• Medium cracks (5 to 10 feet) – $500 to $700
• Large cracks (10+ feet) – $800+

Material Used:

• Epoxy injection (structural) is slightly more expensive than polyurethane (waterproofing).
• High-quality resins cost more but provide longer-lasting repairs.

Accessibility:

Hard-to-reach cracks (e.g., behind finished walls or in tight crawl spaces) may add $100 to $200 in labor costs.

DIY vs. Professional Repair:

• DIY kits cost $75 to $300, but they often lack the pressure equipment and expertise for deep penetration.
• Professional repairs ensure proper adhesion and longevity, making them a worthwhile investment.

At Aqviz, we always recommend professional injection for critical structural or waterproofing repairs, as improper sealing can lead to costly future issues.

When Should You NOT Inject Cracks Into Foundations?

You should avoid foundation crack injection when you see the below behaviors in the foundation.

1. Large structural damage or foundation failure
2. Horizontal cracks in basement walls
3. Extremely wide gaping cracks
4. Active foundation movement to expand cracks
5. Cold or damp conditions for epoxy injection
6. Hairline cracks that do not penetrate the foundation
7. The foundation builds with noninjectable materials like stone, brick, or cinder block.

If you can’t use epoxy crack injection you can use these foundation waterproofing membranes for the foundation. 

Read more about: Ultimate Basement Construction Guide

What is Self-Healing Crack Injection?

Self healing crack injection is a specialized injection system that uses materials like microencapsulated polymers or crystalline waterproofing agents. It activates when exposed to moisture, allowing cracks to seal themselves over time.

What is Smart Crack Injection?

Smart crack injection is an advanced injection method that uses sensors, nanomaterials, or adaptive polymers to monitor crack conditions and adjust sealing properties based on environmental changes.

What are UV Activated Sealants?

UV activated sealants are special sealants that harden or expand when exposed to UV light, ensuring precise control over curing and improving adhesion in difficult repair conditions.

What is Glow-in-the-Dark Leak Detection?

A technique that uses fluorescent or phosphorescent dyes in sealants or injected resins, allowing cracks and leaks to be detected easily under UV or low-light conditions.