Lift a settled slab foundation the right way. Depth and cause determine the method

A slab-on-grade foundation that has settled is one of the most over-diagnosed problems in residential foundation repair. Walk into the average homeowner's living room with a sloped floor and three different contractors will give three different recommendations. Polyurethane foam injection and slab piers, and only one of them is usually correct for that specific slab; mudjacking is not one of Epp's methods. The cause of the settlement and the depth of the void are what determine which method works. Epp Foundation Repair has been lifting slab foundations across Nebraska, Iowa, Kansas, and Missouri since 1994, and the first thing we tell homeowners is that there is no universal lift method. Epp Foundation Repair starts every slab inspection by mapping the settlement pattern with a digital level or laser, identifying whether the slab has dropped at the perimeter, at the center, or in localized spots. That pattern tells us what is happening below the slab. A perimeter drop usually means the soil supporting the edge of the slab has consolidated or eroded. A center drop usually means a plumbing leak created a void, or the original sub-slab fill was poorly compacted. Local depressions usually mean a discrete void from a buried organic, a collapsed sewer line, or expansive clay heave reversing.

A concrete slab has almost no flexural strength relative to its dead load. The slab is rigid enough to span small voids, but once the unsupported area exceeds roughly 3 to 4 feet, the slab cracks and drops into the void. By the time a homeowner notices a sloped floor, the void below is usually larger than the visible cracking suggests. The repair has to fill the void and re-support the slab. Not just lift the visible part. Across Nebraska, Iowa, Kansas, and Missouri, the most common cause of slab settlement we see is consolidation of poorly compacted granular fill placed below the slab during original construction. Slab-on-grade construction in the 1970s through the early 2000s often used on-site loess or fine sand as sub-slab fill, placed in 12- to 24-inch lifts without proper compaction. Over 20 to 40 years that fill slowly densifies, especially after a wet-dry cycle, and the slab drops 1 to 3 inches. In the Kansas-Missouri clay belt the more common pattern is expansive clay heave at the slab center (from a plumbing leak wetting the clay) followed by clay drying and contracting, leaving a void.

The two lift methods Epp uses, and why mudjacking isn't one of them

Polyurethane foam injection (also called polyjacking, or PolyLift in Epp's own job labels). A two-part polyurethane resin is injected through 5/8-inch ports drilled in the slab. The foam expands 20 to 30 times, fills voids, compacts loose soil, and lifts the slab. Foam is the right answer for shallow voids (within 4 to 6 feet of the slab bottom) and for slabs lifting loads under about 1,200 pounds per square foot. It is the fastest method (most jobs cure in 15 minutes, slab is walkable same day) and the least invasive (5/8-inch holes versus 1 1/4-inch holes for the older mudjacking method). Mudjacking (cement slurry injection), for comparison, pumps a cement-and-sand slurry through 1 1/4-inch ports drilled through the slab. The slurry is heavier than foam and applies more lift force, which is why some contractors still use it on very large voids. Epp Foundation Repair does not perform mudjacking on any job, residential or commercial, because the slurry's weight can re-saturate clay soils and recreate the original problem; when a slab needs more lift force than foam provides, Epp goes to slab piers instead. Slab piers. When the void is deeper than 6 feet below the slab, when the settlement is ongoing because the underlying soil layer is unstable, or when the slab is loaded heavily enough that foam will not hold, the right repair is slab piers. A small section of slab (about 18 inches square) is cut out at each pier point. A push pier or helical pier is driven through the slab opening down to load-bearing strata, the slab is lifted on the pier head, and the cut-out is patched. This is the most expensive method but the only one that works when the settlement cause is deep soil consolidation rather than a shallow void.

Epp Foundation Repair sends a diagnostician (not a salesperson) to every slab inspection. The inspector maps elevation across the floor with a digital level or laser, locates the low point and the high point, identifies any visible cracks and measures their offset, checks plumbing for active leaks, and looks for evidence of past or present moisture in the sub-slab fill. On homes built over expansive clay, the inspector probes through one or two test holes to confirm the soil type and moisture content directly below the slab. The diagnosis takes 60 to 90 minutes. We come out of that inspection with a recommendation: foam, slab piers, or occasionally slab replacement. Epp Foundation Repair does not perform mudjacking, so it is never among the recommendations. We will not quote a lift method before we know what is below the slab. ## Regional context: why NE/IA/KS/MO slabs settle the way they do

Nebraska and western Iowa sit on a layer of windblown loess that can run 30 to 100 feet deep. Loess is structurally stable when dry but collapses suddenly when saturated. A soil failure mode called hydrocollapse. A sustained plumbing leak, a downspout dumping water against the foundation, or a high water table after a wet year can trigger hydrocollapse below a slab and produce 1 to 4 inches of settlement in a span of months. In the Kansas-Missouri clay belt, the dominant soil concern is the opposite: expansive clay (plasticity index above 30) that swells 15% when wet and shrinks the same amount when dry. Slab edges over clay heave in spring and drop in late summer, year after year. The 50-plus freeze-thaw cycles NE and IA see each winter add a third stressor by freezing sub-slab moisture and lifting localized sections.

Epp Foundation Repair will tell you up front when slab jacking is not the right service. We will not lift a slab that has structural cracks wider than 1/2 inch through its full thickness. That slab needs to be replaced. We will not lift a slab over an active plumbing leak until the leak is repaired (the leak will recreate the void). We do not lift slabs to correct cosmetic settlement under 1/2 inch unless the homeowner has a tripping hazard or door-clearance problem. Small settlement often is not worth the cost to fix. Slab jacking stabilizes and re-supports the slab; it does not repair existing cracks in the slab, so visible cracks remain visible after the lift (crack repair is a separate step). Epp Foundation Repair is BBB A+ rated and a two-time BBB Integrity Award winner (2011 and 2016). Every slab lift comes with a written scope, a measured lift target, and a written warranty on the work. Foam jobs are backed by Epp's 5-year PolyLift warranty against failure of the material to lift or stabilize due to defects in materials or workmanship; slab pier jobs are backed by Epp's slab pier warranty.

Epp Foundation Repair does not price mudjacking; every quote covers polyurethane foam or slab piers. A Customized Repair Estimate after on-site inspection reflects your scope, soil conditions, and accessibility. If you have a sloped floor, a doorway that has fallen out of square, a crack in a slab that has dropped on one side, or a hollow sound when you tap the floor, schedule a free inspection. The longer a slab settles, the more soil moves out from under it, and the more expensive the eventual lift becomes.