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How To Repair Foundation Cracks In Concrete Walls (Details Guide)

How To Repair Foundation Cracks In Concrete Walls

Foundation wall cracking is a pretty common problem if you live somewhere where the weather is not always on your side. They’re usually caused by some settling of a house on the foundation or the foundation beneath it. Cracks like this, you have to take care of because they can be an entry point for water or cold air to seep through. 

How to Repair Foundation Cracks in Concrete Walls For This kind of crack you have to use a special kind of cement which is hydraulic cement and this is the only kind of cement that expands as it dries. But when it comes to any other kind of cement they will contract slightly when dry. 

If you are thinking about how you can use this cement on the cracks, don’t worry! We have just the right kind of process explained down here with some of the other kinds of repair methods with exclusive tips that you won’t find anywhere else.

How To Repair Foundation Cracks In Concrete Walls

Concrete walls are a common choice for building foundations due to their strength and durability. However, over time, cracks may develop in these walls, which can compromise the structural integrity of your home. Repairing foundation cracks in concrete walls is a crucial maintenance task to ensure the long-term stability of your property. In this step-by-step guide, we will walk you through the process of repairing foundation cracks in concrete walls, from assessing the damage to completing the repairs.

Step 1: Safety Precautions

Before you begin any repair work, safety should be your top priority.

Make sure you have the following safety equipment:

  1. Safety goggles to protect your eyes from debris.
  2. A dust mask to avoid inhaling harmful dust.
  3. Sturdy work gloves to shield your hands from sharp edges.
  4. A first-aid kit on hand for minor injuries.
  5. Adequate ventilation if you’re working in a confined space.

Step 2: Assess the Damage

The first step in repairing foundation cracks is to assess the extent of the damage. Not all cracks require the same level of attention.

Here’s how to assess the cracks:

  1. Examine the size and width of the cracks. Small, hairline cracks are typically less concerning than larger, wider cracks.
  2. Check for any signs of water leakage through the cracks.
  3. Determine if the cracks are structural or non-structural. Structural cracks may require professional assessment.

Step 3: Gather Tools and Materials

To repair foundation cracks in concrete walls, you will need the following tools and materials:

  1. A hammer and chisel or a concrete saw for widening cracks.
  2. Wire brush or a stiff brush to remove debris from the crack.
  3. Hydraulic cement or epoxy injection kit for filling the cracks.
  4. Caulking gun (if using an epoxy injection kit).
  5. Masonry trowel for smoothing the repair material.
  6. Concrete sealer for finishing the repair.
  7. Plastic sheeting or drop cloths to protect the surrounding area.

Step 4: Prepare the Crack

Proper preparation is essential for a successful repair. Follow these steps to prepare the crack:

  1. Use a wire brush or stiff brush to remove any loose debris, dirt, or dust from the crack.
  2. For wider cracks, use a hammer and chisel or a concrete saw to widen the crack to about ¼ inch wide and at least 1 inch deep. This creates a proper surface for the repair material to adhere to.

Step 5: Apply the Repair Material

Depending on the size of the crack and whether it is actively leaking, you can choose between hydraulic cement or an epoxy injection kit:

For non-leaking cracks:

  1. Mix the hydraulic cement according to the manufacturer’s instructions until it reaches a paste-like consistency.
  2. Apply the hydraulic cement into the crack using a masonry trowel, pressing it firmly to ensure proper adhesion.
  3. Smooth the surface of the repair with the trowel.

For leaking cracks (using an epoxy injection kit):

  1. Follow the instructions provided with the epoxy injection kit.
  2. Typically, you will need to inject the epoxy resin into the crack using a caulking gun, filling it from bottom to top.
  3. Allow the epoxy to cure according to the manufacturer’s guidelines.

Step 6: Finishing Touches

Once the repair material has cured, you can apply the finishing touches to ensure a seamless appearance and added protection:

  1. Sand down any excess repair material to make it flush with the surrounding wall.
  2. Apply a concrete sealer to the entire repaired area to protect it from moisture and further damage.
  3. Allow the sealer to dry completely.

Step 7: Clean Up

Dispose of any waste materials and clean your tools promptly. Properly dispose of any hazardous waste according to your local regulations.


Repairing foundation cracks in concrete walls is a crucial maintenance task that can help preserve the structural integrity of your home. By following this step-by-step guide, you can assess the damage, gather the necessary tools and materials, and perform the repairs safely and effectively. Regular inspections and prompt repairs can extend the life of your concrete walls and prevent costly structural issues in the future. If you’re unsure about the severity of the cracks or feel uncomfortable with the repair process, it’s always a good idea to consult a professional for expert guidance.

When To Be Concerned About Cracks In Block Walls

It’s very unlikely that those small hairline cracks that you see on the block walls in your home, maybe above the doors and windows, are actual structural problems. It’s usually just a little thermal expansion that can be fixed very easily by just using a little lightweight spackling. 

But the type of crack that you need to be concerned with are those that are a little wider than that, maybe 3/16 of an inch or more, and where one side of the crack is not level with the other side of the crack, that can indicate some active structural movement. 

Also, if you have any doors in your home that don’t fit the hand quite as well as they used to, another telltale sign. In either of those situations, you need to call out a foundation specialist and allow them to look very closely at that area of your home. 

How To Repair Horizontal Cracks In Concrete Foundation Walls

You repair a horizontal crack in your concrete wall the easiest thing that you can do is buy a crack repair kit from where you will get all the necessary products in a bundle with a proper instruction guide. To use this kit for repairing follow the instructions down below:

How To Repair Foundation Cracks In Concrete Walls

Step 1

The first thing that you need to do is use the extreme 1200 epoxy directly to the wall where the horizontal cracks are. Once you fill in the horizontal gaps you also need to fill in the mortar joints along the horizontal line where the carbon fiber strap is going to lie. 

Step 2

Now you need to trawl them all out so that you have a smooth surface for the carbon fiber strap to lay on. Start from the top and go all the way to the bottom of the wall. 

Step 3

Now it’s time to use the extreme 800 Epoxy. With this epoxy, you have to roll onto the wall. Use a paint pan to make it easier. The goal here is to completely saturate the wall where the carbon fiber star will lay. Start rolling the epoxy from the top going all the way to the bottom. 

Step 4

Use the vertical mortar line as your guide so that you know where you apply the epoxy. Once you’ve covered the wall with epoxy you’re ready to put the carbon strap onto the wall. Start from the top and lay it down on the wall. Once you’re done laying the carbon strap you have to apply another layer of epoxy to make sure it adheres to the wall. 

Step 5

Let the wall cure for a couple of days and then you can come back and paint over the wall. the carbon fiber strap is so unobtrusive that it will hardly show once you paint over it. 

How To Repair Leaking Cracks In Concrete Foundation Walls

In these types of cracks, the injection repair method works best. In this method, you have to fill the gaps with polyurethane injectable grout which is flexible and has a working pressure of 8000 PSI. It will be stronger than the wall itself. 

Make The Crack Bigger

To start with the repair you have to start with a chisel and a hammer to open up the crack. If you are indoors this method of cracking will eliminate the dust and noise. Make sure to clean up any old cement from the gaps so you have a nice surface to work with. 

Chip the gap in a V formation so that you can drill and put anchor plugs in there. The reason for this is, that when you put in your gear rock product you have something to adhere it to and grab it tightly. 

Install Injection Ports

Now you have to install the infection ports into the holes that were spaced out approximately six inches apart and you will be able to install the gear rocks inside the cracks and then the injection fill will be injected through the ports and cap those off. 

Prepare The Injecting Tool

For this job you’ll need a Flo rock anchoring adhesive which can be used for many purposes and one of them is to do the crack injection repairs. This is a two-part system. When you squirt the product out you need to mix the two parts.

Apply Flo rock

Now you have to push the product on those injection points and spread the product on top. You all need to wet the crack before applying the polyurethane once the injection ports are in and the flow rock is set so that the polyurethane gets mixed with the water and expands properly. Let it sit for 60 minutes and get hard before applying the polyurethane. 

Spray The Injection Ports

Use a spray bottle to spray some regular water inside the injection ports to activate the polyurethane and cure this properly inside the cracks. 

Inject The Polyurethane Grout 

Now carefully inject the polyurethane inside the injection ports so they can expand inside and get stronger than the concrete by the time you’re done. When the epoxy starts to push out of the port close down the ports and let it cure for 48 hours. After curing you can cut those ports out or just leave them just like that. 

How To Repair Hairline Cracks In Concrete Foundation Walls

Often people paint over a hairline crack to fill it up. But for some of the slightly bigger ones you will need to go through the filling process. You can use a gap sealant which is a caulking compound. 

  • The first thing you have to do is scrape off the surface to remove any loose strips that may be there 
  • Now push the caulk following the line in thin lines so you don’t make any mess 
  • When you are done caulking, push the filler inside with a raper and scrap off the excess product from the surface 
  • Wipe your blade off regularly so the caulk doesn’t spread anywhere else
  • Once you’ve done that take a paintbrush, dip it in water, and brush over the caulk. This will smooth out the edges and help it blend in

How To Repair Large Cracks In Concrete Foundation Walls

When you have a large crack in a concrete foundation wall you need to chisel out all the loose concrete from the crack to make it more open. Drill the wall and put in grease fittings inside the crack. 

A grade fitting is a fitting that has a gasket on it. So when you drill the while you can put the grease fitting in and tighten the gasket on it causing it to expand and will hold it extremely tight into the hole that you’ve drilled. 

Now you can take a grease gun and put it on the end of the grease fitting to pump a hydro active gel and that gel goes through the crack through the outside and expands through the crack up. 

You also need to brush super slurry outside the crack, which is a crystalline ingredient that grows into concrete. It crystallizes through the porous nature of concrete filling all the nook and cranny of the crack turning it into a waterproof membrane. 

Lastly, you need to use a super Krete product to cover up the crack as a finishing cement that is going to grow around the Hydroactive gel seal from inside to outside. It will also turn the whole crack into one solid pillar. 

How To Fix Cracks In Concrete Block Walls

Mortar joints can fail from top to bottom of foundation walls which can weaken the wall structure. This can leave voids for moisture, damage, and unwanted pests. Block mortar failure can be caused by bowing, shearing, tipping, and water damage. For this repair you need

  • A caulking gun
  • Polyurethane caulk
  • A razor blade

Step 1

The first thing you have to do is, remove about a quarter inch off the tip at an angle. That way you’ll have a nice smooth cut that will allow quite a bit of caulk to come through. 

Step 2

Next, squeeze just a little bit of caulk out so that you can get it right to the tip, and then start filling in the cracks from the bottom to the top. 

Step 3

Use your finger to push the caulk into the crack and just help smooth it out a little bit. Dab it back and forth across the wet caulk to blend it into the cement block. This type of caulk is printable so if you want you can paint over the caulk after about 24 hours. 


Are Cracks In Block Walls Normal?

Throughout the time you might see any type of cracks like vertical cracks, horizontal cracks, diagonal cracks, star-step cracks, long cracks, variable width cracks, etc. You must be thinking, about which one is the worst. Honestly, none of the above. The worst crack you can have is an active crack. That means if you notice the crack is growing over time and you need to get it checked out immediately. 

How Do You Fix A Cracked Foundation Wall Outside?

This kind of crack is considered a non-structural crack and it can be fixed by installing carbon fiber straps or epoxy injections or installing steel-driven push piers. 

What Is The Best Material To Repair Concrete Cracks?

These kinds of cracks are pretty fixable and you only need Ply Sticks which is a pliable product to fix these kinds of cracks.  Clean up the crack with a brush, pack it into the cracks with a screwdriver, hold your torch at a 45-degree angle, and melt the product throughout the cracks to fill it up. 

How Do You Repair Cracks In Concrete Block Walls?

Use a chisel and hammer to widen the crack to a minimum of one-quarter inch. Remove any loose material with a brush. Now apply textured acrylic concrete repair caulk to fill in the crack. Use a trowel to smooth and spread out the product. 

Can You Fix A Foundation Crack From The Outside?

Generally, foundation cracks can be fixed by putting carbon fiber straps along the outside wall using two-part epoxy resin injection which keeps the crack strong from any further damage. 

Can Flex Seal Be Used On Foundation Cracks?

Yes, you can use flex seals on foundation cracks, wall waterproofing, small holes on the foundation wall, etc. 

How Do You Tell If A Crack In A Wall Is Serious?

There are many types of cracks that can rear on the inside and outside of a wall but if you notice the crack growing bigger over time then it is considered a structural crack and you need to be concerned about it.

Final verdict

Being a house owner, you always have to be on edge if you notice any cracks on the walls. No matter if the crack is small or big you need to inspect the causes by calling in professionals. If there is any foundational or constructional lacking that your contractor missed there will be noticeable damage to the walls.