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How to Repair a Cracked Basement Wall

Basement wall cracks can lead to sticky doors, flooding basements, and expensive repairs. In most situations, basement wall cracks are the result of a moving concrete footing caused by poor construction or soil erosion. Basement walls also form the foundation of a home, so most basement wall cracks should be addressed and corrected. Today, we will discuss repairing basement wall cracks from a do-it-yourself perspective and the methods the pros use.

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Why Did My Foundation Wall Crack?

Many times basement wall cracks are a result of an unstable concrete footing. Instability can be caused by poor footing installation, but many times this movement is caused by soil erosion. Soil erosion is usually caused by poor drainage around the basement wall, which can allow water to puddle and flow. If the issue is severe, the footings can actually flood, causing the soil instability to worsen.

In some situations, the erosion is caused by the overuse of sprinkler systems and landscaping installed too closely to the basement wall. Sprinkler systems should be used sparingly, as they tend to pump gallons of water very close to the foundation. When combined with the effects of large roots from shrubbery pressing against the wall, sometimes a crack will form. Basement wall cracks of this nature can be troublesome to repair because they can require the excavation of the landscaping.

Can I Repair a Basement Wall Crack Myself?

If the basement wall crack is less than ¼”” or so wide, chances are good you can repair the crack yourself. Some basement walls are poured concrete, while others are formed from lightweight hollow blocks, often reinforced with concrete and rebar. The thickness of the basement wall may vary depending on the design, but it will always be at least 8” thick, so you may need access to both sides of the wall to make the repair. If you decide access to both sides of the wall below ground is required, it may be better to hire a professional because the project will require digging.

What Will Happen If I Don’t Fix a Basement Wall Crack?

The age, severity, and location of the crack will usually indicate if it is a major issue. For example, small cracks along a mortar joint in a concrete block basement wall are typical and generally are not cause for alarm. Cracks in mortar are common, but mortar should not be falling out. Tiny cracks in mortar typically just indicate the mortar dried quickly and shrunk. Cracks like these can usually be corrected with a simple epoxy crack filler, often applied with a caulk gun.

However, cracks that appear vertically, suddenly, or not in the mortar joint often indicate a serious problem. In most cases, the home’s concrete footer has failed or been broken and will require repair or the problem will likely become worse. In these instances, structural support provided by the footer has failed and the enormous weight of the home has caused the concrete to crack and push into the ground. If this happens, the structural issue must be corrected before any attempt to repair the basement wall crack because or the issue will recur.

How to Repair a Cracked Basement Wall (Step-by Step)

In this example, we will be repairing a basement wall using an epoxy and sealer. We will assume that whatever issue caused the crack has been corrected, and we are left with a crack that is letting water, insects, and possibly radon gas into the basement. Our goal is to seal any crack(s)  ⅛” or larger. We will be using a commonly used kit which will include the materials, but not the tools. The project may require:

  • Hammer
  • Caulk Gun
  • Putty Knife
  • Masonry Chisel
  • Disposable Rag
  • Hair dryer
  • Mineral Spirits

Step 1 Prepare For the Epoxy

Each manufacturer of basement wall crack filler will have slightly different instructions, but most will work in a similar way. The first step is to prepare the crack for the injection of an epoxy and sealer. In this method, we will drive an appropriately sized finish nail into the crack to establish a channel for the epoxy. The nails should be placed every 12” or so and be just wide enough to stay in the crack without falling out. It is important to use a finish nail because a nail with a head will get in the way in a later step.

Step 2 Install the Injection Ports and Sealer

Next, we will need to apply the epoxy. Some kits will require the epoxy to be mixed, while others will come ready to use from a caulk gun, but both methods will require injection ports. To install the ports, simply slide them over the nails driven into the crack earlier, epoxy them into place, and place the included cap over the port. Next, apply a generous amount of crack sealer into the crack as well as the base of the injection ports and allow it to cure for 8-10 hours.

Step 3 Install the Epoxy

After the sealer has cured, we are left with a completely sealed crack with capped injection ports extending from the crack. Using a caulk gun or supplied applicator, remove the cap and inject the epoxy. Ideally, the epoxy will be applied from the bottom most injection port first, working upward. When a lower port is full, the cap is replaced and we move onto the next higher port. 

When epoxy can be seen squeezing out of the adjacent injection port, that port is full so we move on to the next until all of the ports are full and capped. For appearance, it’s a good idea to have a disposable rag dipped in mineral spirits handy to smooth out any sealer extending from the crack. We can also smooth out any sealer that has collected around the base of the ports to help disguise the repair.

Step 4 Finishing Up

The final step in repairing a basement wall crack is to allow the product to cure. With most basement wall crack repair kits the curing period is about a week, but this may be affected by the ambient temperature in the basement. After the product has cured, we can use a utility knife, reciprocating saw, or other tool to cut away the remaining injection ports plastic. We then use a bit of sealer and a putty knife to fill in the void and allow it to cure as well before painting, if desired. 

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