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What is the Difference in Epoxy and Polyurethane in Concrete Crack Injections?

What is the Difference in Epoxy and Polyurethane in Concrete Crack Injections
What is the Difference in Epoxy and Polyurethane in Concrete Crack Injections

This discussion has been around for as long as both products have existed. Like most disagreements, you’ll find the manufacturers on separate sides of the aisle, along with their distributors and end-users. “My product is better” “No, MY product is better.” Anyone get any flashbacks from childhood?

Difference In Epoxy and Polyurethane in Concrete Crack Injections

When it comes to injecting Foundation Cracks, the industry generally uses two products, but there are a couple extra out there as well:

  1. Non-expanding Epoxy Resin

The strongest repair available. Non-Expanding Epoxy bonds best with concrete. This resin will stand the test of time and will not be worn away by water or the elements. The only downside to using Epoxy is that you need a skilled, trained technician to install. This material does not come in the “do it yourself” kits sold at box stores. Again, proper training is required to install correctly, but this is by far the strongest material to inject into a Concrete Crack.

  1. Expanding Polyurethane Foam

While Epoxy is the strongest material used on Concrete Cracks, Polyurethane is the most common. This is due to one overwhelming reason: it is extremely easy to install. So easy, in fact, that kits of it are sold at any box stores and even online. Handy homeowners can purchase the kits and give it a go. Problem with this is that Polyurethane has the highest “Call back” rate in the industry. The material breaks down, and as a skilled technician is not needed for the injection, many times one is not used. Companies can hire and “train” these technicians quickly, with their purpose being to install as much product as possible, neglecting quality. In some cases, Polyurethane is used, like around Sewer Pipes or in large, shifting cracks. Otherwise, Epoxy is best.

  1. Bentonite

Bentonite is an expanding clay that is used on the outside of foundation walls to waterproof them. A foundation can be dug out and this dry powder laid all around. Once the powder comes into contact with water, it expands and seals. The problem with this is the repair is not instant (it may take a few rains to completely seal) and the clay product can come in through the cracks in the wall, so definitely not recommended with a finished basement. Used mostly by construction companies decades ago, we now have moved to more reliable and instant forms of repair, including Epoxy and Polyurethane.

  1.  Hydraulic Cement

This one is merely included to show the “band-aid” patch that is done. Never is Hydraulic Cement anything more than a surface patch for a Foundation Crack Repair. While it will stop water on a temporary basis, this is not a permanent solution. It cannot be done on a Foundation Crack when selling a home and be considered a “professional repair.” Whenever we see this, we see it for what it is, an attempt to stop the water temporarily and save $.

Learn more – Hydraulic Cement: Uses and Applications

Drilling Holes

Very often, we come across Concrete Crack Repairs that have metal injection ports on them. An old-time way of repairing cracks was to literally drill into them and inject an expanding Polyurethane. A technician would drill a hole next to the crack into the foundation, angled toward the crack. The idea being that the port crosses the crack in the wall. Then, the tech will inject the foam.

Problem with this is there is no way to ensure the whole crack is filled. It is a “spray and pray” method. The second problem is that if that repair does not hold, you cannot inject from the inside anymore, it MUST be repaired from the outside.

There are still a couple companies out there that do this old-fashioned method. Why? Because it is what they have always known. And how many times do we continue doing what we have known just for the sake that we know it?

How Foundation Crack Injection Works

Here’s a step-by-step process on how foundation crack injection works.

  1. First, your crack is covered using an epoxy bonding solution. This prepares your crack for the injection.
  2. Next, your crack is injected using a 2-part epoxy solution that completely fills the void, waterproofing and reinforcing your wall.
  3. That’s it. Simple as that.

Summing Up

Just like any industry that uses technology, over time the technology gets better. As part of the industry, it is our responsibility to use the best techniques and materials.

  • Non-Expanding Epoxy Resin is the best product to use for your Concrete Crack Repairs.
  • Polyurethane can be used in certain situations but is by no means a default product.
  • Bentonite can work as well, but is sloppy and can take a few rains to be effective.
  • Hydraulic Cement is a band-aid.
  • Drilling Holes is to be avoided at all costs.

“Not Everything’s Better When Wet”


Austin Werner

Austin Werner is the Owner of The Real Seal LLC, a basement waterproofing and foundation repair company. Austin believes that having a highly trained and happy team is the key to success. This is reflected through hundreds of 5 star customer reviews his company has received online.

12 Responses

  1. Read your article with interest.
    I would appreciate a minute of your time.
    A worker filled a crack (not more than 1/2″ wide with “something”.
    It evidently was an expanding crack filler. It is greenish yellow.
    I have tried to remove the overflow with numerous items. He grinded the crack smooth.
    Not even muriatic acid will remove it.
    Do you think it is polyurethane?
    I need to know, before I try to paint over it.
    Many thanks.

    1. Hi William!

      Happy to help. From what you are describing, it seems they injected the crack with a polyurethane. You should be able to remove it with a drywall knife and smooth it down with sand paper. It is possible they used a hybrid chemical as well that is harder to remove. They shouldn’t have left that overflow and should have cleaned it up prior to leaving the job site. It doesn’t hurt anything, it’s just ugly. You can also try a paint scraper to get it off.

  2. Hi Austin,
    I recently found leaks in my basement. The leak is through the horizontal joint between the concrete stairs, whose shoe is sitting on a concrete foundation wall. The joint might have expanded over time due to different settling along the foundation wall. After any rain, water leaks through this joint, as it is along the nosing of the first step of the stairs; so all water from upper steps runs over this nosing, which now leaks. Although the joint between the concrete stairs shoe and foundation wall is not structural, it is horizontal. What is the recommended solution to stop the leak? Epoxy resin or polyurethane injection? If so, would you inject from inside (in the basement) or outside between the stair riser and tread (through the nosing)? I very much appreciate your time.

    1. Hi Sean,

      If I had a guess, I’d say that there is a door at the top of the stairs going outside as well, correct? The best solution for a horizontal seam at the top of the foundation by the stairs would be Exterior Sealing. The door itself and frame may need flashing repairs or caulking. Outside, if there is a stoop, it may need to be removed to apply an elastomeric tar seal to the outside of the foundation, and then re-built.

      If you are able to see the crack/joint in the foundation, it is possible to inject with epoxy, but I’m worried the water may be coming more from above and it would just push the water to another area.

  3. \ | I am illustrating the side view of the leak in the drawing
    \ | on the left, where it is indicated by x.
    \ ——–
    \ |
    \ |
    \ ———-
    \ concrete stairs |
    \ |
    —————– ———–
    basement | concrete || concrete |
    | foundation || step |
    | wall | ——— sidewalk ————————–
    | |
    | |

    1. Yes, great drawing with what you have available, Sean! I do think the exterior sealing would be the best solution, as well as addressing any sealing/flashing issues with the door there.

  4. |||||||||||||||
    bb |||||||||||||||||||||||||
    bb |||||||||||||||||||||||||
    bbbbbbbbb |||||||||||||||||||||||||||
    bbbbbbbbb |||||||||||||||||||||||||||
    bbbbbbbbbbbb LLLLLLLLLLLLL
    bbbbbbbbbbbb wwwwwww |||||||||||||||||
    bbbbbbbbbbbb wwwwwww |||||||||||||||||
    bbbbbbbbbbbb wwwwwww oooooooooooooooooooooooooooooooo
    bbbbbbbbbbbb wwwwwww
    bbbbbbbbbbbb wwwwwww
    bbbbbbbbbbbb wwwwwww
    bbbbbbbbbbbb wwwwwww
    bbbbbbbbbbbb wwwwwww

    Thanks Austin. Yes, there is an exterior door on the highest step, but the leak is through the nosing of the lowest step. I tried to illustrate the side view again above. Hope this time my drawing works.
    In my drawing,
    L is the leaky line above the foundation wall.
    w indicates the foundation wall.
    b stands for basement area under the stairs.
    o means outside, where the concrete side walk is located.

    1. Thank you, Sean. Yes, this seal will be best done from the exterior. The steps may need to be removed to get to the foundation top, and the door may need to be resealed.

  5. Thanks, will epoxy be a lifetime solution, as the foundation may settle further, or summer/winter temperature variation may open the gap again?

    1. Hello Sean!

      If your foundation is settling, no epoxy or polyurethane will last forever. The foundation settlement must be handled first and foremost. It is often misrepresented in the industry that is okay for a foundation wall to be constantly moving. It is not. If a crack continues to re-open and leak after repair, this means there is some foundation movement that needs to be handled first.

      If the foundation is no longer settling, the epoxy is a lifetime warrantied solution. If it were to ever leak, the company should come back out to repair at no charge.

  6. Thanks, my other question is what epoxy brand do you recommend, since there are many brands out there? Also, I’ve seen epoxy resins coming in one bottle, which does not mix with anything else, as opposed to those you talked in your videos, which come in two bottles, 2 to 1 ratio mixture? Really appreciate your time.

    1. Hello Sean!

      We recommend you go with a contractor that will provide a warranty. There are many epoxy brands out there, and the big box store epoxy is not the top-of-the-line epoxy you want to use. We prefer a 2-part Straight Epoxy mix for most of our foundation crack repairs. Polyurethane can be used, but only in certain situations where Epoxy would not be practical (like pipe penetrations or cracks larger than 1/2″ wide.

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