Why Does Outdoor Concrete 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 and result in uneven concrete.

Primary Causes of Sinking Outdoor Concrete

1) 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.

2) 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.

Check out PolyLevel in Action!

Foundation Repair Solution: Concrete Lifting / Leveling Using PolyLevel

Does your driveway, sidewalk, walkway, concrete steps or patio have problem areas where sunken concrete has caused uneven surfaces and tripping hazards to form?

Conditions where outdoor concrete has already begun to sink are not uncommon in Arizona and are often the result of shifting or a weak soil base or erosion.

Symptoms of Sunken / Sinking Concrete

• Sinking concrete steps or sidewalks
• Cracked, bumpy and uneven driveways or patios
• Cracking and sinking under concrete slabs
• Washout of soils under concrete slabs
• Repeated cracking of concrete slabs

• Strong but light. PolyLevel® weighs only about 4lbs. per cubic ft., compared to 120lbs. per cubic ft. for standard fill material. PolyLevel® ’s light weight makes it useful where denser fill material might impose an undesirable load on weak soils. Despite its light weight, PolyLevel® can support substantial loads; it typically provides greater lifting power than mudjacking.
• Waterproof. Once cured, PolyLevel® will not wash away. PolyLevel® ’s waterproofing properties can be beneficial in certain applications.
• Stable and inert. PolyLevel® does not react with soil or moisture; it will not leach harmful chemicals into the soil.
• Quick curing. Down time is minimized with PolyLevel® concrete repair. Full loading of the foundation, roadway or other structural element can usually happen about 15 minutes after the material is injected.
• Adjustable. Adjusting the density and expansive force of the 2-part foam affords a wide range of geotechnical uses. Lifting force can be adjusted by fine-tuning the chemical reaction that causes the foam to expand. An experienced applicator can factor not only the weight of the structural element but also soil characteristics and temperature and weather conditions. Special formulations are possible for applications where water must be displaced.
• Noninvasive. PolyLevel® injection equipment isn’t bulky, enabling applicators to access confined areas. When properly injected, PolyLevel® is not as messy or disruptive as other slab and foundation-lifting techniques.