Mudjacking and Slab Jacking in Montgomery County, Alabama

What slab jacking is for

Slab jacking, sometimes still called mudjacking, raises a flat concrete slab that has dropped by injecting material into the void beneath it through small ports drilled through the surface. As the material fills the void and pressurizes, the slab lifts. It applies to non-structural concrete: driveways, sidewalks, front stoops, pool decks, patios, garage floors, and interior slabs where fill has settled.

It does not replace underpinning. If the load-bearing footings of the house have moved, the answer is piers, not injection. The distinction is straightforward: slab jacking supports concrete from below by filling space, while underpinning transfers structural load down to competent soil. Filling a void under a driveway is a maintenance repair. Transferring the load of a house is structural work.

Two materials, two use cases

Traditional mudjacking pumps a cementitious slurry, typically sand, cement and water, through injection holes commonly around an inch and a half to two inches across. It is less expensive per unit of lift, it is well proven, and the material is heavy. Cure time is longer and the slab generally should not carry vehicle traffic immediately.

Polyurethane foam injection uses a two-part polymer that expands in place, sets within minutes, and goes in through holes typically around five eighths of an inch. It weighs a fraction of what slurry weighs, it is closed-cell so it does not absorb water, and the slab is usually back in service the same day. It costs more.

On soft or wet clay subgrade in this region the weight difference is not a marketing point, it is the deciding factor. Adding thousands of pounds of slurry on top of soil that already failed to support the slab is a reasonable way to repeat the problem in three years. On firm subgrade where the void came from erosion rather than soil weakness, slurry is perfectly appropriate and cheaper.

Why flatwork sinks here specifically

Concrete flatwork in Montgomery County usually settles for one of three reasons, and knowing which applies to yours predicts whether the repair will hold.

Uncompacted fill. Material placed under a drive, patio or garage at construction and never compacted to specification consolidates over the following years under its own weight and under traffic. This is the most common cause on houses built in the last few decades, particularly on the cut-and-fill pads common around Pike Road, Millbrook and Prattville.

Erosion. Water running off a roof valley, along a driveway edge, or out of a poorly placed downspout carries fine material out from under a slab edge and leaves a cavity. This dominates on the sandier Fall Line Hills ground north of the Alabama River, where the soil moves readily once water concentrates.

Shrink-swell cycling. Slabs poured over expansive clay ride the annual moisture cycle, and as the clay contracts through a dry late summer it can pull away beneath the slab and open voids that never fully close.

Good candidates

• A driveway panel that has dropped at the apron or garage joint, creating a lip
• Walkway sections offset enough to catch a toe
• A patio pitching back toward the house instead of away from it
• A stoop pulling away from the front door threshold
• A garage slab that has settled but is not cracked into small pieces
• A pool deck section that has dropped relative to the coping
• An interior slab in a converted garage or shop where fill has consolidated

Concrete that has broken into many fragments, spalled through, lost its reinforcement, or crumbles at the edges is usually a replacement rather than a lift. A contractor who tells you that is being straight with you, because replacement is the smaller job for them.

What the work actually looks like

Ports are drilled through the slab on a grid, spacing determined by the size of the panel and the extent of the void. Material is injected under controlled pressure while the slab is monitored, usually with a level or laser, and injection moves progressively across the panel so the lift is even rather than concentrated at one point. When target elevation is reached, injection stops, ports are patched, and the surface is cleaned.

Two things are worth understanding. First, a lifted slab will show the patched ports; they are visible, and on a decorative surface that matters. Second, the crack pattern that was there before will still be there afterward, because lifting a slab does not knit concrete back together. If the slab was cracked, it will be a lifted cracked slab.

Fix the water or repeat the job

Slab jacking treats the symptom. If the void was created by water, and it usually was, the water needs correcting at the same time or the material will simply fill a space that is going to be re-excavated by the next storm season. That means extending downspouts, correcting grade along the slab edge, and looking at where sheet flow crosses the concrete. This work is inexpensive relative to the lift and it determines whether you buy the repair once or repeatedly.

What affects the price

The cost drivers are square footage of slab being lifted, how much lift is required, which material is used, how much void volume needs filling, access for the equipment, and whether the slab needs to be back in service immediately. Void volume is the one that surprises people, because it is not visible from the surface; a panel that has dropped an inch may sit over a cavity considerably deeper than that at one end.

Seal the joints once the lift is done

Lifting a slab back to grade reopens or re-establishes the joints between panels and between the slab and the structure, and those joints are where water gets underneath in the first place. Leaving them open means the next few seasons of runoff go straight back into the space you just paid to fill.

The expansion joint between a driveway and a garage slab, between a patio and the house wall, and between adjacent panels should be cleaned out and sealed with a flexible joint sealant suited to exterior use and to the movement expected. Rigid mortar or concrete patching in a moving joint cracks out within a season and does nothing.

This is inexpensive work relative to the lift itself and it is frequently left out of the quote. Ask whether joint sealing is included. If it is not, ask what it would cost to add, and do it at the same time rather than as a separate trip. It is the difference between a repair that lasts and one that becomes a recurring expense.