Mud Jacking Explained: How Foam Injection Fixes Sunken Concrete

If you've got a sunken driveway, patio, or walkway, you may have heard about mud jacking as a faster, cheaper alternative to full replacement. But how does it actually work, and is foam injection really as reliable as it sounds? After lifting hundreds of settled slabs across the Denver metro, CC Concrete LLC breaks down exactly what mud jacking involves and when it's the right fix.

Wondering if your sunken slab is a good candidate for mud jacking? Request a free on-site estimate from CC Concrete LLC →

What is mud jacking?

Mud jacking is a repair method that raises a sunken concrete slab back to level by injecting material underneath it through small drilled holes. The original technique used a cement-based slurry ("mud"), which is where the name comes from. Today, many contractors —including CC Concrete LLC— use a modern polyurethane foam instead, since it's lighter, cures faster, and puts far less stress on the surrounding soil.

Either way, the goal is the same: fill the void beneath the slab and lift it back into place, rather than tearing it out and pouring new concrete.

How foam injection works, step by step

• Small holes are drilled: Typically about the size of a dime, spaced strategically across the sunken area.
• Foam is injected under pressure: A two-part polyurethane foam is pumped through the holes into the void beneath the slab.
• The foam expands and lifts: Within minutes, the foam expands to fill the gap and raises the slab back to level.
• Holes are patched: The small injection holes are sealed, leaving minimal visible trace of the repair.

The entire process is typically completed in a few hours, and the surface can usually be walked or driven on the same day.

Why foam instead of traditional mud jacking?

Polyurethane foam has become the preferred method for most residential repairs, and for good reason:

• Lightweight: Foam weighs a fraction of traditional cement slurry, reducing the risk of further settling.
• Faster cure time: Foam sets in minutes rather than days.
• Smaller injection holes: Foam requires less drilling, making the repair less invasive.
• Precise control: Contractors can control the lift more accurately, reducing the risk of over-lifting.

Is mud jacking right for your slab?

Mud jacking works well when the slab itself is structurally sound and has simply settled unevenly. It's a poor fit when the concrete is already cracked, broken into pieces, or severely deteriorated — in those cases, lifting won't fix the underlying damage, and replacement is the more reliable option.

For a closer look at how to tell the difference, see our guide on concrete lifting vs. replacement.

Frequently asked questions about mud jacking in Denver

How much does mud jacking cost compared to replacement?

Mud jacking typically costs 40 to 50% less than full replacement, generally running $400 to $1,200 per section depending on size and the amount of lift needed.

How long does the foam last?

A properly installed foam lift can last for many years, especially when the underlying cause of settling — like poor drainage or soil erosion — is also addressed.

Will the injection holes be visible?

The holes are small, typically about the size of a dime, and are patched immediately after the lift. Most homeowners find them barely noticeable once sealed.

Can I walk or drive on the slab right away?

Yes. Unlike a fresh concrete pour that needs days to cure, foam sets within minutes, so the surface is typically ready for normal use the same day.

A faster fix, when the slab qualifies

Mud jacking with foam injection is one of the fastest, least invasive ways to fix a sunken concrete slab — but it only works when the concrete itself is still in good shape. CC Concrete LLC gives you a straightforward, honest assessment so you know whether foam injection or replacement is the right investment for your property. Schedule your free on-site estimate today →