Sunken Slab Repair Terms Explained: A Plain-English Glossary
If you are getting quotes to fix a sunken driveway, patio, or garage floor in Des Moines, the estimates can read like a foreign language. This sunken slab repair glossary translates the terms you will see so you can understand what each line means, compare providers fairly, and ask sharper questions. Every entry starts with a plain definition, then tells you why the term matters for your slab and your wallet. Read it once and no contractor jargon should catch you off guard again.
- Concrete Leveling: raising a sunken slab back to level
- Concrete Lifting: another name for the same fix
- Slab Jacking: lifting a slab by pumping material under it
- Mudjacking: leveling with a cement-based slurry
- Polyurethane Foam Injection: leveling with expanding foam
- Self-Leveling Concrete: a pourable overlay that flattens itself
- Settling: the slow sinking of a slab over time
- Expansive Clay Soil: soil that swells and shrinks with moisture
- Frost Heave: ground pushing concrete up in freezing weather
- Void: an empty gap under your slab
- Injection Ports (Drill Holes): small holes drilled to pump material through
- Cure Time: how long before the slab can take weight
- Slab Replacement: tearing out and repouring the concrete
- Crack Filling: sealing cracks to keep water out
- Resurfacing: a thin new layer over worn concrete
- Tripping Hazard: an uneven edge that can catch a foot
- Joint Caulking: sealing the seams between slabs
- Mobilization Fee or Minimum Charge: the base cost to bring a crew out
Understanding Sunken Slab Repair Basics
Most confusion in a sunken slab repair glossary starts here, because the trade uses four or five names for lifting concrete and they overlap. These entries sort out which fix is which.
Concrete Leveling
Concrete leveling is the process of raising a sunken or tilted concrete slab back to its original, even position. Instead of tearing out the slab and pouring new concrete, a crew lifts the existing slab from underneath. It matters to you because leveling usually costs less than replacement and keeps your existing concrete in service. If a quote says "leveling," the provider plans to save your slab, not replace it.
Concrete Lifting
Concrete lifting means raising a slab that has sunk, using material pumped beneath it to push it up. In practice, lifting and leveling describe the same service; some companies use one word, some the other. Do not assume a "lifting" quote and a "leveling" quote are different jobs. Compare the method, the material, and the scope instead of the label.
Slab Jacking
Slab jacking is the general technique of pumping material under a sunken slab to jack it back into place. Both mudjacking and foam injection are types of slab jacking. When a provider says slab jacking, ask which material they plan to use, because the material affects hole size, weight added under the slab, and cure time.
Mudjacking
Mudjacking is a leveling method that pumps a cement-based slurry, sometimes called mud, through drilled holes to lift a sunken slab. It is the older, time-tested approach, and it often costs less than foam. The trade-offs are larger drill holes and heavier material under the slab, which matters on soft central Iowa clay. A good specialist will tell you when mudjacking fits your slab and when it does not.
Polyurethane Foam Injection
Polyurethane foam injection is a leveling method that pumps expanding foam under a slab through small drilled holes; the foam expands, fills the empty space, and lifts the concrete. The foam is light, so it adds little weight to soil that is already giving way, and slabs can usually take traffic within minutes to hours. It typically costs more than mudjacking per job. Providers who offer both, like Des Moines Concrete Leveling Pros, can explain which fits your slab's condition, load, and budget instead of pushing the only method they own.
Self-Leveling Concrete
Self-leveling concrete is a pourable cement product that spreads out and flattens itself to create a smooth, even surface. It fixes dips and rough spots on top of a slab, most often indoors on garage or basement floors. It does not lift a sunken slab; it only smooths the surface. If your slab has dropped an inch at the garage door, you need lifting, not a self-leveling pour.
Why Slabs Sink: The Ground Under Your Concrete
Settling
Settling means the gradual sinking of a concrete slab as the soil beneath it compresses or washes away. It is the most common reason driveways, sidewalks, and patios end up uneven. A little settling is normal in the first years after a pour; a slab that keeps dropping or tilts toward the house is worth a look. Settling is also the main problem that sunken slab repair in Des Moines is built to fix.
Expansive Clay Soil
Expansive clay soil is soil that swells when wet and shrinks when dry, moving anything that sits on top of it. Central Iowa has plenty of it, which is a big reason Des Moines slabs sink and crack more than homeowners expect. Wet springs swell the clay, dry summers shrink it, and your slab rides that cycle year after year. A provider who mentions clay soil is thinking about why your slab sank, not just how to lift it.
Frost Heave
Frost heave is upward movement of soil and concrete caused by water in the ground freezing and expanding. Iowa's freeze-thaw winters push slabs up in cold months, and the slabs do not always come back down evenly in spring. The result is uneven concrete at joints and edges. Heave and settling can look similar, so ask the estimator which one they think caused your problem.
Void
A void is an empty pocket under a slab where soil has washed out or compressed away. Voids leave the slab unsupported, so it cracks or drops under weight. Leveling fills the void at the same time it lifts the slab, which is why the fix lasts instead of just looking better for a season. If an estimator mentions void filling, they plan to support the slab, not only raise it.
On the Job: Glossary of Sunken Slab Repair Process Terms
Injection Ports (Drill Holes)
Injection ports are the small holes drilled through a slab so leveling material can be pumped underneath it. Mudjacking holes are usually about the size of a soda can top; foam holes are closer to the size of a dime. After the lift, the crew patches the holes with cement. Ask how many holes the job needs and how visible the patches will be on your finish.
Cure Time
Cure time is how long a repair material needs to harden before the slab can carry normal weight. Foam typically sets within minutes to hours; mudjacking slurry needs longer, often a day or more, before you drive on it. Cure time decides when you get your driveway back, so ask for it in writing on the quote. It is one of the clearest practical differences between the two methods.
Slab Replacement
Slab replacement means removing the old concrete entirely and pouring a new slab in its place. It is the right call when concrete is badly crumbled, shattered into small pieces, or sunk beyond what lifting can recover. Replacement costs more and takes longer than leveling, including days of cure time before use. An honest estimator will tell you when your slab is past saving, because lifting broken rubble wastes your money.
Finishing Touches and the Paperwork
Crack Filling
Crack filling is sealing cracks in concrete with a flexible material to keep water and debris out. It matters because water that slips through a crack washes out the soil below and freezes in winter, making the crack and the sinking worse. Crack filling often gets bundled with leveling as a protect-the-fix step. On its own, it is a low-cost maintenance item, not a structural repair.
Resurfacing
Resurfacing means applying a thin new layer of cement product over worn or flaking concrete to give it a fresh, uniform surface. It is a cosmetic fix for surface damage like pitting and scaling. Resurfacing does not lift anything, so a sunken slab needs leveling first, then resurfacing if you want it to look new. Quotes that combine both should list them as separate line items.
Tripping Hazard
A tripping hazard is a raised or sunken edge in a walking surface, often where one slab section sits higher than the next, that can catch someone's foot. Sidewalk lips of even half an inch cause falls, and they are a common reason homeowners call about leveling in the first place. Fixing the hazard usually means lifting the low slab so the edges line up. If a walkway serves guests or an aging family member, this is the term that turns a cosmetic issue into a safety one.
Joint Caulking
Joint caulking is sealing the gaps between slab sections with a flexible sealant so water cannot get underneath. Those joints are the main path water takes to wash out soil and create voids. Caulking after a lift helps the repair last through Iowa's wet springs and freeze-thaw winters. Expect it as a small line item on many leveling quotes.
Mobilization Fee or Minimum Charge
A mobilization fee, or minimum charge, is the base amount a contractor charges just to bring a crew and equipment to your home. Small jobs, like one sunken sidewalk square, often get priced at the minimum even if the work itself is quick. Knowing this helps you group repairs; leveling the walkway and the patio in one visit usually beats two separate trips. For a fuller picture of what drives price up or down, see our guide to what sunken slab repair costs.
Using These Terms
With this sunken slab repair glossary in hand, you can read a quote line by line and know what each item does: the lift, the void fill, the crack filling, and the joint sealing. You can also ask the questions that separate a specialist from a script, like which method fits your slab and how long the cure time runs. That is enough to compare bids with confidence and spot the ones that skip steps.
If you need concrete leveling, Des Moines Concrete Leveling Pros can help.
Related guide: sunken slab repair — Complete Guide
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