Basement Floor Leaks And Cracks – Causes & Repair Options

Have you noticed water seeping through basement floor cracks? If you have then you have a serious problem on your hands.

Leaky floors mean that moisture is constantly flowing into your basement, and when there is moisture there is mold growth.

Mold as we know is dangerous to human health, as it can be both toxigenic and allergenic at the same time. That aside, who wants to live in a room that constantly leaks?

I’m guessing you don’t, and that’s why you’re reading this article in the first place.

Not to worry, I’ll be giving you all the information you need regarding basement floor leaks and cracks, their causes, and how you can fix them.

Keep reading!

Causes Of Cracks In Basement Floor

There are 3 main reasons why there are cracks in your basement floors.

Let’s go over them one by one.

Shrinkage: Shrinkage can be attributed to the poured concrete walls and floors drying faster than they should. When it dries up too fast, it causes the concrete to shrink, and this causes the floor to crack.

Shrinkage usually happens just after a building has been constructed.

Settling: Settling occurs when the ground beneath the basement floor keeps on compressing under the weight of the poured concrete.

When this happens, cracks will be formed as a direct result of ground compression. The cracks are usually minor in cases where the ground beneath the basement floor compresses for a short time.

However, if the ground continues to settle for longer periods, then the cracks will be wider and more problematic.

Movement: This is probably the most common cause of cracks in basement floors. When the soil under the floor shifts, the cracks begin to form.

Similar to settling, the shorter the movement time, the smaller the cracks, and vice versa.

Should I Seal My Basement Floor?

The answer to this question is yes, you should seal your basement floor to protect your space from further leaks and their consequences.

When your basement floor leaks, serious damage can be done to your structure if not repaired quickly.

The damages that crack causes can run into thousands of dollars in repair, and I’m sure you don’t want to spend huge sums of money on something you could have prevented earlier.

Leaks can also leave your carpets soaked, and in turn, cause them to produce an awful smell.

That aside, damp carpets and basement floors are perfect environments for dangerous mold to grow. And as I have mentioned earlier, mold is dangerous to human health.

Stains can also occur from leaks, and that messes up the general aesthetics of your basement.

The good news is, sealing your basement walls and floors isn’t a difficult task. You can have a contractor do that for you, or you can do it yourself.

Don’t panic if you have no idea how to go about it, I’ve broken down the processes for you step by step.

Leaky Basement Floor Repair

Follow these simple steps to fix your leaking basement floor.

Step 1: Find the leak

You can’t stop a leak if you have no clue where the water is coming from. Finding the leak will be a lot easier if the basement is unfinished, as there will be fewer obstacles to deal with.

Typically, anywhere you find a pool of water is where the leak will be. Another pointer to the source of the leak is a damp foundation seam.

If you can’t spot the leak, then you can just clean up the water in the basement and observe the floor. It will only be a matter of time before the water starts trickling out again.

In the case of a finished basement, you may need to raise your carpet, pads, or other floor decorations to be able to trace the leak.

As you can expect, the leak in your basement floor is definitely from a crack in the floor or the seam around the area where the floor and foundation meet.

Still, you have to be sure that the water you see on your basement floor isn’t dripping down from the walls.

Step 2: Prepare Your Surfaces

To repair your leaky basement floor, you will first have to ensure that the area is clear and ready to be fixed. This will involve moving away from any furniture or property that may be obstructing your view.

You also need to be sure of the type of sealer you plan to use. Some sealers and patching materials cannot be used over painted surfaces.

So check the product label to be sure you are using the right sealer for that particular painted surface.

If the sealer cannot adjoin with your painted basement floor, then your efforts and money will end up being a waste.

One more thing you have to do before applying the floor sealer is to sweep across the space to remove dust particles that may prevent the sealer from properly adjoining with the floor.

You can also use a vacuum cleaner to pick up all the debris before you begin.

For basement floor cracks that are wider than 25 inches, you certainly have to clean the debris from the cracks before applying the sealer.

If the crack is still loaded with water, then you have to wait until it dries off before application.

Step 3: Apply Patching Compound And Waterproofing

Carefully apply the patching compound into the floor cracks as instructed on the pack. Once the compound has settled, you can then proceed to add the waterproof mix.

In a case where you cannot stop the moisture in the cracks, then be sure to use a water-soluble sealer. If you don’t, the sealer will not adhere to the edges of the leaking joints and floor cracks.

Once again, take a look at the manufacturer’s instructions on the pack to be sure of the compound to water ratio.

Step 4: Apply Sealant

Grab a paintbrush and apply the sealant into the pores of the cracks. A hard bristled brush will be your best option.

I have to warn though, do not to apply the sealant on the concrete if it hasn’t been treated with the patching compound and waterproofing material. Also, do not apply it more than 2 inches away from the leaking area.

The next step is to wait and allow the sealer to dry. You can leave it overnight to become hard, then apply a second coat for better fortification.

Cost To Fix Heaving Basement Floor

Fixing your heaving basement floors could be a simple or difficult task, depending on the extent of the damage done. If you feel the job is too much for you to handle, then you have no other choice but to hire the services of a professional.

But what would all this cost? Stick around and find out.

Average Cost of Minor Repairs

Simply put, the more severe the damage is, the more it will cost you in repair. This is largely a result of the number of materials the contractor will use, the number of laborers required, and the time the job will take.

You can expect to spend less on minor repairs such as small surface cracks caused by shrinking. In this case, a simple concrete overlay can be used to seal the cracks.

As for the cost, well it’s really on the low side. A basic concrete overlay will cost between $3 and $7 per square foot.

You actually have a second option, which is to seal the cracks yourself with a commercial sealant. You can go to any home improvement store near you to buy one. It costs between $9 to $20 per bottle.

Average Cost of Major Repairs

A basement floor that has passed through extensive damage over time will cost a lot more to fix. In a case where the floor is beyond saving, then you will have to break and replace the floor in its entirety.

Although this would be the more expensive option.

Keep in mind that strengthening and stabilizing (underpinning) a floor or slab consumes a lot of time and requires hard labor. Underpinning one section of your sinking basement floor could cost you from $3,500 upwards (depending on the level of repairs needed).

For general strengthening, you can expect to spend about $300 per square foot.

Other factors can determine how much you’d be spending on basement floor repairs, besides the size of the cracks.

One of such factors is your area of residence, as we all know that some states are generally more expensive to live in than others.

Another factor that will play a role in price is the reputation or status of the contractor you are dealing with. Consider these factors as you proceed.


You can fix cracks and leaks in basement floors yourself or with the help of a professional, but it all depends on the level of damage done.

Be sure to use the information provided in this article to get your basement floors fixed.

Thanks for reading!

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