Concrete Crack Repair Methods

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Use this section as a guide to determine which product you should use. Applied Technologies has been supplying the waterproofing industry since 1998 with quality concrete crack repair materials and equipment. This includes concrete cracks in foundations, retaining walls and concrete slabs. Use this page as a guide to help you decide which repair method is best for your concrete crack. This section covers cracks such as hairline, actively leaking, structural, slab cracks or a floor crack in a concrete basement. Read on to learn the best concrete repair method.

Concrete Foundation Crack Repair - The Basics

The best way to repair a concrete crack in a foundation wall is by injecting it from the inside. The repair is quick and is therefore inexpensive. Injection ports are attached to the surface and a paste is applied over the crack surface. This cures and forms a strong seal to hold the injected epoxy or polyurethane in place. Then the liquid epoxy or polyurethane resin is injected into the crack. Once inside the crack, the soil on the exterior and the surface paste on the interior holds the liquids in place as they react. And then the repair is complete!

Polyurethane Foam vs Epoxy Injection

By far the number one question our new customers ask is "Should I use epoxy or polyurethane foam to fix my basement crack?" The vast majority of cracks in a foundation wall that leak water should be repaired using a polyurethane foam. This is for several reasons.

More economical than epoxies
Easier to use
Cure faster
Expand and fill voids
Most cracks do not need re-inforcing from epoxies

Polyurethane Foams

Urethanes react with moisture in the crack to foam and expand inside the wall. This completely fills the void from top to bottom and all the way through. In fact, the urethanes can expand up to 30x their initial volume. Urethane foams are flexible and move with the expansion and contraction of a foundation wall from freeze/thaw cycles. Much less resin is needed with urethane foams since they expand in volume. That makes them much more economical than epoxies. Finally, urethane injection is relatively easier to do than an epoxy injection.

Polyurethanes Pros

Less expensive
easier to use than epoxies
Inject actively leaking cracks
Fills larger width cracks
Flexible

Polyurethane Cons

Not a structural repair

Polyurethane Foundation Crack Repair Kits

Polyurethane Resins

Epoxies

Epoxies weld the crack together and restore structural strength. The bond strength can be much higher than concrete. Movement is eliminated in the concrete wall during expansion and contraction cycles.

Foundations that are moving or have a continuing stress load on them may need additional repair methods to stabilize the wall and prevent further damage. The epoxy is stronger than the concrete, but the continued stress load may cause the concrete to crack again.

Epoxy Pros

High strength weld
Stronger than concrete
Structural repair of crack

Epoxy Cons

More expensive than urethanes
Bond strength is lower when done in a wet crack
Concrete can re-crack if the wall is still moving
Epoxy Concrete Basement Crack Repair Kits

Epoxy Materials

Is the Foundation Crack a Structural Defect

It can be assumed that a crack is structural if:

Runs at 45 degrees or less
Is horizontal
Is over 1/2" wide
The wall has deflected across the crack

Nearly 100% of concrete foundations crack. This is because as the concrete cures, it shrinks in volume. This shrinkage causes stress on the concrete and to relieve that stress, it cracks. This is okay and the foundation is designed to handle the crack. The most common places on a foundation wall where this occurs at the corner of a window, where the wall "steps down" or in the middle of a long wall. These cracks are nearly vertical in nature and usually 1/2" or less. We recommend using a urethane foam for these cracks.

For a crack that is horizontal, runs at 45 degrees or less, or the wall has deflected, it can be assumed that the crack is structural and an epoxy should be used. The epoxy will restore the strength of the concrete wall. Please remember that cracks greater than 3/4" wide, horizontal or have deflection indicate that there is a stress on the foundation that must be remedied. Even though the epoxy will restore the concrete's strength, the stress may be more than any epoxy can withstand.

Low Pressure or High Pressure Injection for Concrete Cracks

Where to use low pressure

Wider than hairline (wider than a fingernail or 1/32")
Surface of the wall is dry

Low pressure injection using surface mounted ports, single or dual cartridge resin cartridges and a hand trigger injection gun is the most common method to repair a crack. Professional waterproofing contractors know that this system works for 90% of cracks that they encounter.

Click Here for low pressure injection polyurethane kits

Click here for low pressure injection epoxy kits

Where to use high pressure

Narrower than hairline (less than fingernail thick)
Actively leaking water
Previously repaired cracks
High pressure injection kit

High pressure injection uses drill in place packers to get the resin into the crack. A grease gun filled with resin is attached to the packer. This process is used on actively leaking, hairline or cracks that have already been filled with hydraulic cement. Higher pressures are needed to get into a hairline crack than a trigger injection gun can generate. Also, water on the wall surface from actively leaking cracks will not allow the surface paste used with low pressure systems to adhere to the concrete.

Click here for high pressure injection kit

Actively Leaking Concrete Basement Cracks

A foundation crack that is actively leaking water can only be repaired by using a polyurethane foam. They set up much faster than an epoxy so the water will not push all of the resin out before it has cured and expanded.

Our Acta-Leak Concrete Crack Repair Kit will stop the water from coming in a basement.

Because the surface of the concrete wall is wet, a surface paste cannot be used to adhere ports or to keep the resin in the crack as it reacts. But it is still possible to perform the repair by using the high pressure method.

Holes are drilled alongside of the crack and packers are inserted. The polyurethane resin is then placed into a grease gun. The grease gun is attached to the packers and the resin is pumped into the crack. On contact with water the polyurethane will begin to foam and expand, stopping the water.

Click here for the Acta-Leak Crack Repair Kit

Hairline Concrete Wall Crack Injection

At Applied Technologies we define a basement crack as "hairline" if you cannot get a fingernail into it. This is roughly 1/32" wide. Cracks as narrow as this can let in water. A low pressure injection using a manual dispensing gun may or may not be able to generate enough pressure to get the resins into the crack. A good tip on injecting them by low pressure is to warm the cartridges in water. This will make the resin thinner and more likely to enter the hairline crack.

For cracks that are extremely narrow, the high pressure system can be used to repair these cracks. This is done by drilling packers into the wall and using a grease gun loaded with resin to inject the materials. The grease gun method can generate much higher pumping pressures to get the resins into the crack.

The Acta-Leak Concrete Crack Repair Kit will repair hairline cracks.

Previously Repaired Basement Cracks

This technician will use the Acta-Leak Crack Repair Kit method to repair this crack sealed with cement

If your foundation crack was repaired previously by hydraulic cement, it is still possible to inject a urethane foam. The technician who first fixed the leak chiseled a vee-notch in the wall and then packed it with cement. Applied Technologies does not recommend you chisel out this cement.

We recommend the Acta-Leak Crack Repair Kit for cracks that have been previously repaired.

Basement Wall to Floor Seam Leak

It is common for the seam formed where the slab meets the wall to leak. This water usually is coming up from below the floor due to the water table rising after rains. Injecting a urethane foam into this seam will stop the water in the area it is injected into. However, we DO NOT recommend injecting urethane foams of any type or manufacturer into this seam. This is because if the water is not able to enter the basement area, high water pressures can develop that causes a structural problem in the concrete slab or wall. A functioning drain tile and/or sump pump system is required for a proper long term solution for this problem.

Concrete Block Walls and Injections

A static mixer is placed over a cartridge of concrete crack injection material. The material will then be injected through a surface port and into the foundation crack

Static mixers snap tightly into our surface ports. Surface ports allow the concrete crack injection materials to enter the crack.

Injection of polyurethane concrete foundation crack repair material. All repairs are done from the inside of the basement.

Extremely tight hairline concrete cracks can be injected with a high pressure grease gun.