Why Does Concrete Sink and Settle?
Concrete sinks when the soil beneath it erodes, a tree root decays and leaves a void, poorly compacted fill settles, or expansive clay shrinks in dry weather. Identifying which one is at work matters before you repair: the cause determines whether leveling will be a lasting solution or a temporary one.
Soil Erosion Beneath the Slab
The most common cause of concrete settlement is erosion of the soil beneath the slab by water flowing under it. When water from rain, drainage, or underground sources flows under a concrete slab, it carries fine soil particles with it. Over time, this erosion creates voids empty spaces beneath the slab that the concrete eventually sinks into. Mudjacking and polyjacking both address this directly by filling the voids and lifting the slab. Correcting the drainage problem that allowed water to flow beneath the slab reduces the likelihood of re-settling.
Tree Root Decay
Tree roots that grow beneath concrete slabs push up the slab as they grow, then when the tree is removed or the root dies and decays, the void left by the decaying root allows the slab to sink into the gap. This produces a very specific pattern: a slab that was lifted and cracked by a root, then sinks into the void as the root decays. Leveling fills the void and lifts the slab, but does not prevent future root intrusion from remaining trees. (For more on this, see How Much Does Concrete Leveling Cost?.)
Poor Original Compaction
Concrete slabs poured over inadequately compacted fill continue to settle as the fill compresses under the slab’s weight and traffic loads. This settling is most common in areas where fill was placed for construction purposes (building pads, utility trenches, landscaping) and the concrete was poured before the fill had fully consolidated. Leveling addresses the resulting voids; however, if fill continues to consolidate, re-settling is possible. (For more on this, see Can I Prevent Concrete From Sinking Again After Leveling?.)
Expansive Soils
Clay soils expand when wet and shrink when dry, causing concrete slabs to heave upward in wet periods and sink below level in dry periods. This cyclical movement eventually cracks slabs and causes settlement. Leveling a slab on expansive soil is a less durable solution than on stable soil, because the same soil movement that caused the original settling will continue after leveling. In expansive soil areas, mudjacking or polyjacking provides temporary improvement but is not a permanent fix without addressing the soil condition. (For more on this, see Mudjacking vs. Polyjacking vs. Replacement: Which Is Right?.)
Concrete Leveling Cost at a Glance
| Cost Factor | Typical Range | Notes |
|---|---|---|
| Mudjacking (cement-soil slurry) | $3 to $6 per square foot | A 100-sq-ft sunken section runs $300 to $600, though contractor minimums of $450 to $950 keep a job that small near $500. Ready for traffic in 24 hours. |
| Polyjacking (polyurethane foam) | $5 to $25 per square foot | The same 100-sq-ft section runs $500 to $2,500. Ready for traffic in 15 to 30 minutes. |
| Full concrete replacement (comparison) | $8 to $18 per square foot | including demolition and disposal. Mudjacking sits well below it, while foam on a badly settled slab can approach it. |
Cost figures on this page were checked against published pricing on August 28, 2026. How we source cost data.
Add-ons: drainage correction ($300 to $4,000), crack repair ($150 to $800), joint sealing ($300 to $1,000). These are not included in leveling quotes but are needed for a durable result.
Planning Your Project Budget
The cost ranges in this article are based on industry data and are intended as planning benchmarks, not fixed prices. The actual cost for your project depends on your specific home, your local labor market, the current price of materials, and the scope the contractor confirms after a site inspection.
Always get at least two written quotes on equivalent defined scope before committing to any home services project. Wide price variation between quotes usually reflects differences in material quality, scope completeness (what is included and what is not), or contractor overhead and experience level rather than simple price competition.
Use the cost data in this article to ask better questions during the quoting process: What material is included? What does that per-square-foot or per-linear-foot rate include and exclude? Are permits, cleanup, and disposal included? What is the warranty on labor? These questions turn a quote into a comparable basis for decision-making.