Is My Basement Floor Sinking? [How To Identify And Fix A Sinking Concrete Floor]

You might have noticed some unusual changes on your basement floor and are now starting to worry. Are you suspecting that the floor is sinking? Well, we have consulted the experts to give you an in-depth understanding of what could be going on and how to solve it.

Your basement floor may be sinking if you see some of the signs below. Let’s demystify this problem by showing you how to identify the signs before the damage gets worse:

  • Cracks in the foundation
  • Cracks in the walls, or above door frames and windows
  • Doors and windows not opening easily
  • Uneven floor

Continue reading to learn how you can tell your basement floor is sinking. We'll also delve into the causes, the repairs to do, and how much they cost.

A large deep crack in concrete foundation of house, Is My Basement Floor Sinking? [How To Identify And Fix A Sinking Concrete Floor]

How Can You Know If Your Basement Floor Is Sinking?

A sinking floor, if not attended to promptly, can compromise the structure of your home. It is therefore paramount to know the signs early enough so that you can tackle the issue before the damage degenerates further.

Cracks In The Foundation

Deep crack in old brick wall

Cracks in the walls of your basement are an obvious sign that your floor is sinking. However, not all cracks are due to this reason. So, how can you tell when a crack is due to a floor sinking?

Cracks Widening With Time

This type of crack appears like a thin hairline on the surface of the concrete floor and is not harmful to the structure of your home. They are caused by loss of moisture when the concrete and mortar harden, leading to shrinkage, but do not change over time. 

On the other hand, if you notice cracks years after building your home, or the cracks become wider or longer with time, then there is some movement going on in your floor.

Wider Cracks At The Top

If the cracks in your basement wall are much wider at the top than at the bottom, then this could mean that your floor is sinking. It is advisable not to fill the cracks right away. Instead, call in a professional to establish the real problem.

Cracks In The Walls, Or Above Door Frames And Windows

Cracks appearing in an interior wall

Cracks in the drywall and plaster could mean there is a problem with the foundation such as the basement sinking or it could be due to poor plastering. If repaired cracks open again after being repaired, then it is an indication that there is a problem with the floor.

Also, drywall cracks at the corners of the door and windows at any level of your home could be a sign there’s a problem with the foundation in your basement. You may also notice the nails popping out of the drywall.

Doors And Windows Not Opening Easily

Worn out internal parts of doors and windows and high humidity levels could prevent your doors and windows from opening easily, or it could be a sinking problem causing the doors and windows to fall out of their frames. 

You can tell if this problem is due to the floor plummeting downwards by placing a four-foot level on top of your door or window. If it is level, it could be due to another problem, but if it is not level, then there is a likelihood the floor is sinking. 

Also, if you are living in an old home and the windows stick only occasionally, then it could be a moisture-related problem as higher levels of moisture causes the wood to expand.

Check this four-foot level on Amazon.

Uneven Floor

An uneven concrete floor in your basement or a sagging wooden floor in the upper rooms should be of great concern. This could be due to a sinking basement floor or due to other reasons such as shifting of the interior columns in the basement or crawlspace.

Another reason causing the unevenness could be due to floor joists hanging or sagging, which are normally common especially in homes with a crawlspace.

This problem is almost always due to a sinking floor.

What Causes Your Floor To Sink And How To Repair?

The movement of soil make the crack between pile and tile floor

A floor in the basement that is sinking is a very serious problem because it can affect the overall foundation of your home. It should be addressed as soon as you notice the signs explained above.  

The following are the most common causes of basement floors sinking:

Rising Foundations

Some soils have chemical properties that absorb a lot of water causing the foundation to be raised upwards, creating a void under the basement floor. If not repaired, it can cause the floor to sink.

Also, after the water is absorbed, it dries up after some time. The cycle of absorption and drying can cause fissures to be created on the basement floors.

You can solve these problems as follows:


Have a look at this jack hammer on Amazon.

This method of filling the void under the foundation involves drilling small holes on the concrete floor and then injecting in material to fill the void. The materials used vary from one company to another, but the most common is a limestone or cement slurry often referred to as “mud” and the process is referred to as mud-jacking.

The slurry dries and hardens within minutes lifting the concrete floor. It is not invasive and is therefore not messy.

Replacing The Foundation

If there is extensive damage to your basement floor due to sinking, the only option is to replace the foundation. This is a highly invasive, expensive, and work-intensive method. 

Ideally, all the landscaping and yard around your home will have to be removed, the foundation excavated, and the soil dumped around the house. 

Temporary supports will be installed, the wall rebuilt, and the supports removed. Finally, all the dirt and soil that was initially removed will be returned. 

In most cases, the soil will take a year or so to settle, though it can take longer depending on the type of soil, the amount of rainfall, and the materials used to build.

If you do the foundation correctly on stable soil, the settling experience should be minor. 

Pillar Pads Sized Wrongly

During the building of a home, pillars are installed in the basement or the crawl space to transfer the weight of the home to the soil below. If they are the wrong size, they will not provide the proper weight distribution. Instead, they will sink and may sink with the basement floor.

Most professional contractors will address the issue by jacking and lifting the house upwards. They will jackhammer around the support beams and pour in footing pads. This restores the house to its former position, and floor concrete is poured again.

Soil Erosion Below the Basement Floor

Flooding or heavy rains can cause the soil under the foundation to be eroded over time, leading to an empty space under the foundation. This means your floor no longer has support and could cause the floor to sink.

Your contractor will most likely address this issue by installing foundation piers and may combine them with mud-jacking. A foundation push pier is the ultimate solution to supporting a home that has a sinking foundation or wall. It is suitable for use in most soil conditions. 

Foundation Push Piers

This pier is installed by first removing the soil and exposing the foundation footing where it will be driven.

The foundation bracket is fixed securely onto the current footing and sections of the pier are pushed hydraulically through the bracket until stable soil or bedrock is reached.

The weight of your home will then be transferred to the piers, and onto the soil bearing the load. When this is done, the contractors will then try to lift the foundation, elevating the foundation back to its primary position. 

How Much Does It Cost To Repair A Sinking Floor?

Concrete construction of basement

Thinking about the repair costs can overwhelm you. However, look at the repairs as a way of preventing further damage to your basement floor, which could end up being more expensive, and also as a way of prolonging the life of your home. 

A permit will be needed to repair your foundation, and the costs will be determined by the extent of the damage, the materials used, and the labor.

Generally, contractors can install piers at a cost ranging between $1,000 and $3,000 per unit, while mud-jacking would cost between $500 and $1,300.

In Closing

A sinking basement floor could signal major structural damage to your home, which should be addressed as soon as you spot the signs.

A professional is best placed to handle any repairs needed after assessing the damages and providing the most appropriate solution. 

Have a look at our previous posts on what to do when there are cracks on your basement floor, and how to build a basement on clay soil:

Cracks In A Basement Floor Are They Normal And When To Worry

Can You Build Basement In Clay Soil?

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