Why Is My Concrete Sinking Over Time?

Concrete sinks over time and there are so many reasons behind it. Read on to find out why! 

Why Is My Concrete Sinking?

Concrete is one of the most durable, easy to produce, and economical building materials. That is why it is the most commonly used material for building foundations, exteriors, and pavements.

Similar to the many other building materials we know of, concrete is still prone to cracking, chipping, crumbling, and sinking. Some companies call this slab settlement – the sinking or movement of a concrete slab when the soil underneath it is no longer capable of carrying its weight. This frequently happens on driveways, walkways, sidewalks, garage floors, and foundations.

Primary Cause of Sinking Concrete

Slab settlement usually comes in forms of uneven, cracked, or sunken concrete. Homeowners usually discover it by seeing concrete that’s uneven, cracked, or sinking. 

There are repairs that can be done to get the sunken concrete lifted again, but without addressing the core reason behind sinking concrete, a repair is only temporary. The concrete will soon crack, crumble, and sink again.

To be more prepared in case your concrete sinks, here are some of the most common reasons for slab settlement:

Water Issues

The main reason for slab settlement are water issues. Water can damage both the concrete, the soil underneath it, and the structures that surround it. Heavy rain or flooding can cause these to weaken and soften which would further cause the concrete to break and sink.

During winter, water also freezes and thaws, and this causes the soil beneath a slab to crumble and break. When it weakens, it will no longer have the same capability to support the slabs.

Water can also flow over and under the slab from downspouts that run directly on the ground beside concrete sidewalks and driveways, causing the soil underneath to wash out completely and leave an empty space where support for the concrete used to be. 

Washout of Soils

All structures are built over soil and over time, it can lose its integrity or completely get washed out. This can happen due to weather conditions that can push water underneath the slabs, getting the soil to move along with it, leaving the concrete slabs with nothing to support its weight.

When the soil under the slabs gets washed out, it creates an empty space that the concrete will sink into eventually.

Dry Soil Conditions

Different seasons bring about different conditions that all affect the integrity of the materials used to build and support a structure. 

Some seasons bring droughts that can cause soils to shrink. These extended periods of dry conditions can result in unstable sub-surfaces and empty spaces that lead to sinking concrete.

Similarly, when droughts end and rains start pouring, the dry soil will become wet and moist. This condition of soil under concrete will not be strong enough to support and lift it, further causing the slabs to fall.

Lack of Slab Support

Concrete slabs are built on top of strong soil because it needs the support to keep it even. When one part loses the support it has underneath, concrete slabs can crack, break, shift, and slip away.

Some constructions use artificial support such as lumber and wire, but typically, especially in residential properties, the concrete slabs are placed on soils that are strong enough to support them as pavements, driveways, and such. 

Types of Soil

Different soils have different load-bearing capabilities. When the capacity is exceeded, the soil will compact and settle and cause the concrete slabs to sink, crack, crumble, and become uneven. This is very common on driveways and sidewalks – areas that are utilized more often by people and vehicles. 

Another thing to note is the possibility for the soil underneath a concrete slab to settle and get compact on its own, without needing pressure. Soil generally has large amounts of clay that will shrink substantially when it gets dry. As the clay shrinks, the soil crumbles, and that causes the concrete slab to sink and break. 

Frost Heaving

Frost heaving is the expansion of soil when the temperature dips below freezing. This happens during winter, when melting snow penetrates the soil beneath concrete slabs. The freezing water causes the soil to swell upwards and the concrete slabs to shift and move from where they are settled. 

When temperatures get back to normal and the ground dries out, the soil contracts and shrinks to sizes that are no longer enough to support the slabs on top of it. Frost heaving leaves the sections of the slabs unsupported and more susceptible to sinking.

Improper Grading

Improper grading is when land slopes towards or away from a home’s foundation caused by rainfall. When this happens, the water runs off and penetrates the soil easily, creating moisture under the slabs. 

Excess moisture in soil creates instability that leads to sinking concrete. Improper grading is frequently a factor for properties that need concrete repair. 

Tree Root Growth

When trees grow near concrete, the roots can extend into the soil underneath. As the tree grows, the root system also does. This can cause irregularities in the soil supporting the concrete slabs. 

As the root system further grows and irregularities in the soil occur, it becomes more sensitive to external factors such as foot traffic and weather conditions. When that happens, concrete slabs can sink, crack, and buckle without the change of weather and water damages.

Burrowing Animals

Naturally, there are many underground animals that burrow through soil. Mice, rats, and other animals can find its way around your property and burrow its way through the soil that supports your concrete.

When underground animals burrow through soil, they create semi-permanent pathways for them to find their way around a certain area. This creates gaps in the soil under your concrete slabs, causing them to sink and break.

Poor Craftsmanship

There are plenty of external factors that affect your concrete and cause slab settlement, but sometimes, it can also be because of the materials used for the concrete slabs themselves. 

Not all concrete mixes are the same and they depend on the budget given to the contractors in charge of the job. When on a very tight budget, contractors may not have other options but to use sub par quality materials which create generally weak concrete slabs. 

Other than budget, lack of proper training and knowledge on mixing cement can also cause the slabs to be unstable even with proper support around and underneath. 

Fixing a Sinking Concrete

Sunken concrete is not something you have to live with forever. You have better options for concrete repairs around you and it is just a matter of when you are planning to get it done!

Our professionals at Extreme Spray Foam repair slab settlement using high-quality spray foam. Call us today and get your concrete fixed and back to its optimal condition! We proudly serve all properties in Northeast Georgia and Upstate South Carolina.

Extreme Spray Foam Is Proudly Serving Georgia & Upstate South Carolina


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