Why Does Concrete Sink?

Written By Leah LeitowPublished on 06/2/2021Updated on 10/7/2025

Concrete is used throughout the construction world for several reasons, namely its durability and longevity. But, like all building materials, even concrete can fall victim to damage for a variety of reasons. This is true not only for the concrete within your home, but outside your house – patios, pool decks, sidewalks, and driveways – as well.

Let’s take a closer look at why the concrete structures on your property might be sinking and failing, as well as what you can do to protect them.

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What Causes Concrete Damage and Sinking?

Damage to concrete structures in, under, or around your home can come from many sources. Broadly speaking, the causes of damage either begin in the soil under your home and other structures on your property, or in the climate itself.

Soil-Based Problems

The soil underneath a property is just as important as the strength of its foundation. It could be argued that it is more important. After all, your foundation rests on this soil and relies on its stability just as the structure of your property relies on its foundation

Soil-based problems come in these main forms: instability and erosion. Poorly compacted soil is a fairly common problem that starts when a property is being constructed. The movement of soil around the site during construction disturbs it. Though construction companies take the time to replace and compact the soil, it is never as stable as it was before excavation. If soil is poorly compacted, it can begin to shift and settle, leaving voids between your home and the ground.

Erosion is often connected to poorly compacted soil and climate-based factors and issues. Heavy rainfall, for example, can wash away exposed soil that is poorly compacted and has nothing to hold it in place. As the soil washes or blows away in periods of intense dehydration, it leaves concrete structures under-supported. This can lead to settlement, cracking, and sinking.

Climate-Based Issues

Climate-based issues can affect your property either from below, through the soil, or from above by direct contact with concrete structures. The main climate factors that affect soil are excess moisture, extreme dehydration, and frost heave.

If the climate you live in is very wet or humid, the amount of water in the soil can vary drastically. Rainfall can increase saturation levels, of course, but there are also some areas that simply have very marshy soil. Incredibly wet, loose soil can lead to subsidence in all kinds of structures. This process of sinking can cause cracking and further sinking. Excessive dehydration, by contrast, shrinks and cracks. When it does this, it leaves large gaps which your foundation can fall, or settle, into.

Frost heave is what happens when the moisture in the soil freezes and expands quickly. This can cause a hump or bulge in your basement or flooring. If subsequent dehydration causes the soil to shrink, however, this bulge can collapse and become a depression.

Street Creep

Street creep is a unique problem that can put huge amounts of pressure onto your property. You see, it’s not just the concrete on your property that you have to worry about; the concrete slabs on the street impact your home, too. In winter, the cold weather causes concrete slabs to contract and shrink, opening up the spaces between them. This can allow small stones and other debris to pack into these spaces. When the slabs expand once more in summer, they may not be able to displace this debris and as a result, will put pressure on your driveway and property.

Each of these issues is unique but inescapably linked to the others. At the very root, however, most problems in concrete structures within your home come down to a mix of moisture and pressure, whether it be in the soil under your home or the air around it. Moisture is the biggest enemy of concrete. After all, concrete is a porous material; when placed in a humid environment, it will absorb water. Most concrete foundations, walls, and flooring can deal with a certain amount of moisture and pressure, of course. They are designed to cope with it. However, if there is too much water or pressure or not enough support, they will begin to crumble and crack.

Animals and Tree Roots

Animals and tree roots can also do significant damage to the concrete structures you have around your home. If, for example, you have trees with invasive root systems planted within 20 feet of a concrete structure, the soil beneath your structures can shift unevenly, causing your structures to sink. Burrowing animals can leave behind similar gaps.

You’ll never know which of these forces is causing problems for your property, though, if you don’t know what signs of damage to look for. If you think something may be going amiss out in your yard, you’ll want to keep an eye out for unusual animal behavior around your property, gaps in the foundation line near your home, and pooling water or unusually damp soil near your porch, patio, driveway, or other concrete structures.

Signs of Damage and Sinking

Of course, while bulges, tilting, and depressions are sure signs of damage to concrete floors or other structures on your property, are other more subtle signs that you can look out for. Learning to recognize these signs will help you to catch damage before it snowballs into a huge, structural problem. Smaller signs of damage or the onset of sinking or settlement in your property’s concrete surfaces within your home. These are:

Spreading Cracks, Pitting, Flaking, and Staining

Cracks in concrete are fairly common and can come about as a house or other concrete on the property settles. If the cracks are static and do not seem to be letting in water, you can relax a little. If, however, the cracks are spreading this is a sign that the structures in question are under continuing strain and may need to be repaired or bolstered.

The top layer of concrete also can flake away, leaving the surface patchy and pitted. If moisture seeps into the pores of untreated concrete and becomes trapped, this moisture will expand and turn to ice during temperature drops and freeze-thaw cycles. This expansion can destroy the concrete’s pores, weaken the concrete, and lead to slabs that experience pitting and flaking. Concrete’s porous natures also makes it vulnerable to staining when left untreated.

Dampness, Mold, and Mildew

If you notice a sudden rise in humidity within your home and you can’t find any obvious reason for it– like a leaking window or burst pipe–then damage to your concrete floors is likely. If you find that certain floors or other areas are wet to the touch, then you should begin your investigation with these areas.

Mold and mildew are sure to follow wherever there is dampness, but they can also cause problems. As well as being unsightly, certain species of mold can be dangerous to your health and property. They can even attract pests like cockroaches. Mold and mildew will, of course, concentrate on the spaces that are most humid.

Repairing Sinking or Cracked Concrete

The possible solutions for cracked, sinking, or bulging/bowed concrete are numerous and the best possible repair methods are decided by the underlying causes. Cracks and depressions caused by a damaged foundation, for example, require different solutions than those caused by excessive hydrostatic pressure in the soil around your home.

FSM provides several specialized solutions including foundation repairs and concrete lifting. If the problematic concrete is closely tied to your foundation, you may need a solution like foundation piers to stabilize and potentially lift the concrete slabs back into place. If the concrete is not foundation in nature – a separate patio, driveway, sidewalk, or pool deck area – revolutionary polyurethane injections can be used to lift the concrete. This is a quick, economical, non-invasive way to address the unstable soil underneath the concrete slabs and permanently repair them.

If you are interested in learning more about these techniques or are ready to fix your sinking concrete once and for all, contact the expert team at FSM to schedule a free inspection and repair quote. It pays to have experience on your side, as well as repairs tailored to your unique repair needs.

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FAQs

Will there be any visible signs of repair after concrete lifting?

The repair process requires drilling small holes in the concrete, which are then filled and sealed after lifting. These patches may be visible but can often be made to blend with the existing concrete over time.

Can all concrete slabs be lifted?

Most sunken or uneven concrete slabs can be lifted, including driveways, sidewalks, patios, and pool decks. However, severely damaged slabs that are cracked or crumbling may require replacement instead.

Why does concrete sink?

Various factors can lead to concrete sinking, including:

Soil settlement or erosion
Water oversaturation from rain or snow melt
Inadequate drainage
Root intrusion from trees
Freeze-thaw cycles
Installation issues

Addressing these foundational issues promptly is crucial to circumvent future structural complications and damage to the foundation. The experts at Foundation Systems of Michigan will identify the root causes and recommend suitable repair strategies during a free inspection.

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