Injection Basement Waterproofing With Epoxy & Polyurethanes

In this guide, we will discuss injection basement waterproofing.

Cracks in your basement concrete walls or floors may seem like a little issue, but it’s really not. And while it’s not a matter of immediate urgency, a little line today may develop into wider cracks in the future.

When the lines become wider, it will lead to water seepage and compromise the structure of your home.

Cracks in your basement are usually a result of dry shrinkage and thermal movement, but thankfully there are several means by which they can be sealed.

One of such approaches is injection-based waterproofing. This method is easy to execute, and it doesn’t require that you carry out any excavation. It is also cheap, so you don’t have to worry too much about the cost.

You can repair poured foundation cracks with a low-pressure injection of epoxies or polyurethane foam. In the case of concrete floor crack repair, you can also use some epoxies and polyurea materials.

GUIDE: Bentonite Waterproofing

You can execute this task all by yourself if you’ve had some prior experience. Then again, you can hire a seasoned professional to do it for you.

Regardless of whether you do the job yourself or hire a contractor, injection basement waterproofing shouldn’t take you more than an hour or two to complete.

Let’s discuss all you need to know about injection basement waterproofing.

Keep reading!

How Do Crack Injections Work?

It is very common for basements to leak, and even if a small crack isn’t leaking today, it will do so eventually.

Over the years, crack injections have been a common approach to fixing separations, and more contractors are beginning to tow the same line when it comes to foundation repairs.

This shouldn’t come as a surprise, since crack injection repairs are permanent, effective, and inexpensive.

According to statistics, basement waterproofing contractors have a lower than a 1% call back rate for injection basement waterproofing work. Some contractors even warranty the injection repair for the lifespan of the building.

A spring-assisted dispensing tool that is similar to a caulking gun can be used for injection basement waterproofing. The tool uses a dual cartridge system, which holds the epoxies and polyurethane foam needed for sealing the cracks.

This type of repair aims to fill the cracks from the front to the rear with epoxy or polyurethane. If you’re fixing the basement walls, then a low-pressure injection is recommended to guarantee that the cracks are filled up.

Low-pressure injections are great for cracks that are 0.002 to 1 inch wide for walls that are about 12 to 13 inches thick. Besides the walls, it is also ideal for filling cracks in concrete floors and ceilings.

Epoxies Or Polyurethanes, Which Is Better?

Homeowners tend to be confused when it comes to choosing between epoxy or polyurethane when it comes to fixing cracks in their basement’s concrete works.

As for which material is better, there isn’t any real answer to that. It all depends on the severity of the cracks and what you intend to achieve.

Keep in mind that both of these materials can seal the cracks, so you can expect your contractor to go with the material they have more experience with.

There are some general rules though.

In a case where the crack needs to be structurally fixed, and you need the area to be stronger than the concrete surrounding it, then epoxy is your best bet.

But in a case where you’re fixing the crack solely to prevent water leakages, then polyurethane is the material you should use.

Let’s discuss both materials separately.

Epoxy Injection Waterproofing

There are different viscosities of epoxies for crack injections. There is the ultra-thin kind, as well as the paste-like type. Both of which are meant to seal cracks of different sizes.

It is recommended that you use the viscosity required to inject at a crack with pressures less than 40 PSI. As a simple rule of thumb, the wider the crack, the thicker the material required.

One of the major upsides of using epoxies is that they have impressive comprehensive strength. At 12,000 PSI, it surpasses that of most concrete.

For this reason, epoxies are best suited for cracks that require only structural repair.

As for the downside of using epoxies, you will find that they cure very slowly.

It takes several hours to become hard after application. Although this can also be considered an advantage, because the longer it takes to harden, the better the chances of it flowing into the tightest crevices.

On the flip side, the flow can move out of the back of the crack before it gets hard if the backfill outside the wall is separated from the foundation.

Keep in mind that behind every crack is a void, which is why the crack leaks in the first place.

Polyurethane Injection Foam Waterproofing

If you are concerned that the filling material can leak out behind the crack, then your best choice would be polyurethane foam.

This material is elastomeric and it sets very fast, which is why they are great for only crack sealing and waterproofing, but not a structural repair.

Thanks to their elastomeric nature, they can accommodate slight concrete movement, which allows the seal to remain intact.

They have the ability to harden and foam in a matter of minutes after they are injected, and this reduces the chances of the material flowing out of the crack while still in a liquid state.

Even if a little leak out, it will find the void and fill it up.

This material is ideal for a simple crack filling procedure. However, they add basically no extra comprehensive strength, although that is not needed in most residential applications.

With a low-pressure crack injection, basement crack and foundation repair kits can fix cracks from within, which takes away the need for soil excavation.

The kits come with all the materials and tools required to seal cracks which span from 10 to 60 feet in length.

Some even come with a user’s manual, which provides a step-by-step guide to see you through the process.

Depending on the type of crack you’re dealing with, you can choose a repair kit that uses either epoxy or polyurethane foam.

Polyurethane crack injections are ideal for non-structural leaking cracks, which develop as a result of concrete shrinkage. On the other hand, epoxy injection kits are great for more severe cracks which are threats to the structural integrity of your walls.

How To Execute A Successful Low-Pressure Crack Injection For Basement Waterproofing

Follow the steps below to carry out the process appropriately.

As we have mentioned before, the type of polyurethane or epoxy you use depends on the uniqueness of each job.

This includes the width of the crack, the thickness of the walls, and other conditions.

Step one: Install the injection ports

The surface ports, which are small, hard plastic tubes, are the components that allow you to pass the sealing materials into the cracks. Thanks to this, you will not need to drill into the concrete before you begin the repair.

This reduces the workload by a significant amount, as there will be no need to clean up debris afterward.

You should place the base of the port directly over the crack and bond it to the surface using an epoxy paste.

As a rule of thumb, you should space the ports about an inch apart per inch of wall thickness.

Step 2: Seal the surface

With an epoxy adhesive, seal over the surface ports and any exposed cracks.

The paste should cure in a time frame of 20 to 40 minutes, and this will provide a surface seal with amazing bond characteristics, which will hold firm under the pressure from the injection.

The exposed crack is covered with the paste, so only the portholes will be uncovered.

Step 3: Inject the crack

Start injecting at the lowest port on the wall up until the epoxy or polyurethane starts to spill out of the port above it. Doing this will indicate that the crack has been filled up to that level.

Now you can plug the first port using the cap then move up to the following port. Repeat this process until you have filled up the entire crack with either of the filling materials you choose.

Allow the compression spring on the dispensing tool to press the sealing material into the crack utilizing slow and constant pressure. This will reduce any chances of leaks, and permit adequate time for the material to fully enter the crack.

Step 4: Remove the ports

You should wait for about 48 hours at room temperature so the epoxy or polyurethane to cure and enter deep into the cracks.

You can use a hammer or trowel to remove the injection ports. You can improve the appearance of the surface by chipping off the extra epoxy surface seal with a sanding disk.

You can also use a sealer that can be peeled off after the repair has been completely cured.


Injection basement waterproofing is cost-effective and easy to execute. You can do it yourself using the information provided here, or hire a professional.

Thanks for reading.

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