How To Fix Crumbling Concrete Basement Floor? (Solved)

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Concrete floors are prone to crumbling over time, and nature plays a significant part. However, a few other causes play in, damaging your neatly made basement concrete floors.

So, what should you do when that happens? And how best should you fix your crumbling basement floors to prevent similar cases in the future? This article offers insight into the best ways to fix a crumbling concrete basement floor.

Why Is the Concrete Floor in the Basement Crumbling?

Your basement’s concrete floor may crumble after some time, and that’s reasonably expected if it’s constantly exposed to degrading elements like water and acids like sulfates.

Moreover, with constant strikes as you work on your DIY projects, the hammering and pressure you create give way to crumbling. Concrete combines aggregates, including sand, gravel, cement, and crushed stones.

Another common cause of a crumbling basement floor is the unintentional mixing of the material that makes up the concrete with a mineral material called pyrrhotite.

Pyrrhotite is an iron sulfide, once this mineral is reached by water or the constant humidity that concentrates on a basement floor it starts a chemical interaction that affects the integrity of the concrete causing crumbling.

Pyrrhotite will not only affect the basement floor but also the walls and foundation, so one way to quickly and visually rule out or confirm this problem is to look for crumbling concrete in the basement walls.

The cement usually acts as the holding matter, sometimes weakening if exposed to water over long periods.

Pyrrhotite is a very serious problem that can structurally affect a house, but the truth is that the concrete floor can be weakened on its surface by other chemical reactions of concrete aggregates with moisture and this is something that does not compromise the structure and only affects aesthetically.

Acids are the most damaging since they disintegrate the material, weakening bonds and compromising the cohesion between particles. Combined or working together, all these factors lead to the eventual concrete floor crumbling.

How Do You Fix Crumbling Concrete in a Basement?

A few best non-intrusive and cost-effective ways of fixing crumbling concrete in a basement exist. However, some homeowners would go all in, removing the floor and replacing it with a new one.

That may work and perhaps solve the problem pretty well. But it’ll take a lot of labor and time and, of course, cause more disturbance.

Replacing damaged concrete floors can cost between $10 and $25 per square foot, which can weigh heavily on your pockets. So how best do you fix a crumbling concrete basement floor?

Sealing the cracks on crumbling concrete floors is the best and most recommended way of fixing crumbling concrete floors. However, it’s usually best to be quick and start working on your floor immediately. It starts crumbling before the damage becomes more profound.

Here’s how you can fix the crumbling concrete basement floor:

Step 1: Clean the Entire Area and Apply Some Bonding Agent – Ensure that you remove every bit of crumbled cement. You can chisel the loose sides to dislodge the loose parts and remove the crumbles by sweeping them away.

Using a vacuum cleaner will ensure that the entire area is clean. You may also scrub the area with water and a tough bristle brush, but that’s only necessary if vacuuming isn’t satisfactory enough. You may brush some bonding agent on the crack or the damaged area.

Step 2: Prepare and Pour a Consistently Thick and Creamy Mortar – A mason trowel and concrete mixture should be fine. However, ensure that it’s thick and consistently creamy to bond well.

You can also ensure that it mixes well by using an electric mixer and achieve perfect uniformity. Finally, apply the mortar on the damaged floor, spreading it evenly using a trowel. Ensure that you spread properly and level the new concrete by scraping any remaining or protruding bumps.

Step 3: Let the New Concrete Dry Out – You should give your new concrete about 24 hours to dry out properly. You can also cover the floor using cardboard box pieces if, perhaps, it’s under direct sunlight.

While doing so, please ensure that it doesn’t come directly in contact with the wet concrete. Your crumbled concrete basement floor should be fixed after these three essential steps.

How Best Do You Repair an Old Concrete Basement Floor?

An old concrete basement floor is far, much different from a crumbling one. However, remember that old floors also crumble, and repairing them using the steps above should fix them.

Restoring your floor’s initial glitter should always do the trick, and you can either resin, polish, or dye it. Moreover, you can also paint it to give it a newer appeal that’s better for the eyes.

However, time always takes a toll on concrete, and if the damage is profound (Such as crumbling, cracking, and breaking), patching and sealing should work fine.

Can New Concrete be Poured Over Old Crumbling Concrete?

You can pour new concrete over an old, crumbling one. That should offer an additional layer that covers the old floor, giving it a much better appeal. However, you must remove the loose crumbles by chiseling them out, cleaning the area using a brush, and vacuuming it.

That should guarantee a more lasting new concrete that properly binds with the old one. Applying a binding agent should facilitate binding and ensure it stays there permanently.

Is It Normal for Basement Floors to Crack or Crumble?

Basement floor cracking is expected and shouldn’t worry you much. Even better, you don’t have to worry about compromising support and impacting your home’s structural integrity.

A basement floor is constantly exposed to moisture and water saturation, it is normal for the concrete floor to weaken and for cracks and crumbling to appear.

However, cracked and crumbled basement floors can be unsightly, which makes repairs a priority. Besides, cracks create water to seep in, which should prompt emergency repairs if that’s the case.

Is There a Way to Paint the Crumbling Concrete Floor?

Directly painting your crumbling concrete floor won’t make it any better. However, using a floor primer should consolidate the surface better and make painting much more possible, offering a medium for the paint to bond to.

However, the best way that guarantees a better result is to fix it by sealing the cracks and damaged parts with new concrete. That should make the surface more uniform, and painting should be quite a breeze and high quality.

How to Seal Crumbling Concrete

You can seal crumbling concrete by pouring a new cement layer on it. However, it’s best to ensure the area is clean to facilitate proper binding. Remember that once crumbling begins, it creates more weak points that may need to be removed.

Removing every bit of loose cement should make the process more fruitful instead of just applying the concrete without checking adequately. Sealing can be a much better option if replacing it may take time, more effort, and cost highly.


Fixing crumbling concrete basement floor is easy, and even though it shouldn’t worry you about your home’s compromised structural integrity, repairing it helps restore your basement’s initial glitter.

Remember that floor crumbling is expected if predisposing elements like acid and water are present and vigorous activity puts pressure on the floors as you work on your projects.


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