Sinking & Settling Outdoor Concrete in NYC

photo of a sinking concrete sidewalk with cracks in Saint Albans

When a concrete slab sinks, it often cracks as well. This sidewalk not only looks bad; it's also unsafe for pedestrians and bicyclists.

Notice how much newer the damaged concrete is than the stable slabs around it. Replacement was not a long-term solution in this case, because the original problems with the soil were not addressed.

The Problem:

Broken and/or misaligned concrete (sidewalks, patios, driveways, etc.) poses a safety hazard, while also detracting from appearance and real estate value.

Telltale Signs:

  • Sinking Concrete Steps or Sidewalks
  • Concrete Driveways & Patios Sinking Or Tilting Down
  • Cracking & Sinking Sections Of Slabs
  • Washout Of Soils Under Concrete Slabs

What Caused It:

The soils underneath the concrete were either washed away or unable to support the weight of the masonry.

How to Fix It:

We fix smaller concrete slabs that have settled using a technique called mudjacking, slabjacking or grout injection. This process involves pumping a mixture of water, soil, sand, and Portland cement underneath the slab to fill voids and (in some cases) raise the slab back up.

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Why Does Outdoor Concrete Sink?

Concrete is heavy! When the soils underneath a concrete slab are unable to support its weight, the slab will sink. If part of the concrete slab is supported by soils and other sections are not, the unsupported pieces may crack away from the other section.

The soils underneath an outdoor concrete slab can fail to support the weight of the slab for these two primary reasons:

A hoofprint in the mud, showing compacting soils

Soil Shrinkage, Compaction & Settling

Different types of soil have different load-bearing capacities. When a soil's load-bearing capacity is exceeded, the soil will compact and settle.

It's also possible for the soil beneath a slab to settle and compact of its own accord. Soil that contains large amounts of clay and/or silt will shrink substantially when it gets dry.

As the soil compacts underneath a concrete slab, the unsupported slab will sink as well, usually cracking in one or more spots.

Water washing away mud and sediment in rainy weather.

Washout Of Soils

The soil that is underneath your driveway, patio, or concrete steps may not necessarily remain there to provide adequate support for the concrete element.

As water moves underneath your concrete slabs, it can wash away the soil that's supporting the weight of the concrete. As this happens, it creates a void, or empty space, underneath. Over time, with nothing to support it, your concrete slab can begin to sink or cave in.

Repairing Residential Concrete Slabs

A severely damaged, sinking sidewalk with washed out sand underneath in Whitestone.

Water has washed away the soils underneath a section of this concrete sidewalk.

As it did, a void, or hollow area, was created underneath the concrete. With nothing to support it, the concrete eventually collapsed.

Mudjacking is a repair technique that can stabilize sinking concrete by filling in empty spaces or voids with a mixture of "mud" or "slurry." This is a fast, effective process that can usually be completed in less than a day.

This "slurry" mixture is composed of water, soil, sand, and Portland cement that will harden to create a stable supporting base underneath the concrete slab.

Mudjacking will do more than simply stabilize the sinking concrete. As the slurry is pumped underneath the concrete slab, it will also lift the slab, potentially returning it to its original position.

As slurry cures, it creates a long-lasting, sustainable solution for supporting the weight of the concrete above.

Slurry will not be affected by compaction and washout like your previous soils were, and mudjacking (aka slabjacking) costs much less than demolishing and reconstructing sunken concrete.

More about concrete slab mudjacking.

Contact Us For Settling Concrete Slab Repair in NY!

Our in-house contractors at Quality 1st Basement Systems specialize in structural stabilization for foundation problems of all kinds -- including sinking, settling outdoor concrete slabs like the ones found in sidewalks, patios, steps, walkways, driveways, and many similar surfaces.

We offer free settling outdoor concrete quotes throughout our New York service area.To schedule your appointment, contact us by phone or e-mail today!

We proudly serve Brooklyn, New York City, Bronx, areas such as Flushing, Staten Island, Manhattan, Queens, Elmhurst, Ridgewood, Astoria, and nearby.

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