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Repair, lift or replace: reading a failing slab
Sunken driveways, tilted walks and cracked patios are everywhere in Greater New Orleans, and for good reason: soft, wet ground keeps moving long after the concrete is poured. The right fix depends on why the slab failed and whether that cause is finished. Some slabs can be patched, some can be lifted back into place, and some need to come out entirely. This page explains how to read the damage, what each option can and cannot do on settling soil, and how to judge a repair or replacement quote.
Read the damage before choosing the fix
Different problems leave different marks. Hairline cracks that stay tight are usually shrinkage and are cosmetic. A slab that is still in one piece but has dropped at one end or along one edge has lost support underneath. Many cracks radiating from one area, or pieces that rock when stepped on, suggest a base that has washed out or ground that has settled unevenly. A flaking, rough surface is a different issue altogether, caused by weak finishing or wear.
Before calling anyone, look at the pattern and note when it started. Did the problem appear after a heavy storm, a plumbing repair or work on a nearby tree? Is it getting worse? Photos taken a few months apart are useful evidence for the contractor.
Settlement that keeps going versus settlement that has stopped
On much of the south shore, soft clay and organic soils keep consolidating slowly for years, and water drawn out of the ground contributes to the gradual sinking the region is known for. A slab that settled over loose fill after construction may eventually stabilize. One sitting on soft, compressible ground may keep drifting downward.
That distinction shapes the choice. Lifting a slab that sits on ground that is still settling may need to be repeated in future years. Replacing it without addressing the ground may only reset the clock. Ask the contractor what they think caused the settlement and whether it is likely to continue, and weigh the options with that in mind.
Lifting a slab with foam or grout
Slab lifting is common in the region. The contractor drills small holes through the concrete and pumps material underneath, either a cement-based grout, often called mudjacking, or an expanding polyurethane foam. The material fills voids and raises the slab back toward level. Foam is lighter, which can matter on soft ground; grout is heavier but has a long record of use.
Lifting works best when the slab is largely intact and has settled as a unit. It is a poor fit for a slab shattered into fragments, one with a flaking surface, or one resting on soil that a leak or bad drainage is still carrying off. Holes are patched afterward and usually remain faintly visible. Ask how many holes are planned and how they will be filled.
When replacement makes more sense
Replacement is often the better choice when the concrete is broken into several pieces, the surface is badly worn, the slope is wrong and sends water toward the house, or the original slab was too thin for its use. It is also a chance to fix the base, improve drainage, change the layout and add reinforcement.
A replacement quote should say how the old slab gets demolished and removed from the site, what will be done with the ground underneath, and how the new slab will be built. If the problem came from soft soil, look for a plan to remove unsuitable material and build a compacted base, not just to pour fresh concrete on the same ground.
Patching cracks and surface damage
A hairline or narrow crack can be routed clean and packed with an elastic sealant that keeps out rain and weeds. That slows further damage but does not change why the crack formed. Cracks that open and close with the seasons need a flexible filler, not a rigid one that will pop out.
Thin surface resurfacing products can refresh a worn but structurally sound slab. They depend on a clean, solid surface and generally will not hide or stop movement below. Where a slab has shifted or broken, a surface coating usually cracks along the same lines. Ask for honest expectations about how long a patch is likely to hold.
Water, leaks and drainage behind the damage
Water is behind much of the damage. A downspout draining against a slab edge, a leaking pipe under a driveway, or a low spot that holds water after every storm can soften the soil and carry base material away. Fixing the concrete without fixing the water tends to repeat the failure.
Look at where water goes during a heavy rain and share photos with the contractor. If a plumbing or sewer leak might be involved, having it checked before repairs begin is worth doing. Drainage changes such as redirecting downspouts, adding a drain or correcting the fall are often part of a lasting fix.
Matching new concrete to old
Replacing only part of a driveway or walk saves work but leaves a visible difference. Fresh concrete starts out paler and more even in tone than its weathered neighbor, so a perfect blend is unlikely. Choosing to replace whole panels between existing joints, or a full section up to a natural break, makes the change look intentional.
Where a new section meets an old one, dowels can help keep the joint level. Decorative concrete is especially hard to match, so for stamped or colored surfaces ask whether replacing a larger area would look better.
Questions for a repair or replacement quote
- What do you think caused the damage, and is it likely to continue?
- Would lifting, patching or replacement work here, and why?
- If lifting, which material, how many holes, and how will they be filled?
- If replacing, how will the ground and base be improved?
- What drainage changes are included?
- How will new concrete meet the old, and how will the color difference be handled?
Repair, lift or replace — common questions
Should I lift or replace my sunken driveway?
If the slab is mostly in one piece and has dropped as a unit, lifting it with foam or grout is often worth considering. If it is broken into many pieces, badly worn, too thin or sloped toward the house, replacement usually makes more sense. On ground that keeps settling, either option may need follow-up later. A contractor can inspect it and explain which suits your slab.
Does slab lifting last on soft New Orleans soil?
Lifting fills voids and raises the slab, but it does not stop the ground below from consolidating. Where settling came from loose fill that has since stabilized, a lift can hold for a long time. Where the soil is soft and still compressing, the slab may drift down again and need another lift in the future. Ask the contractor what to expect for your site.
What is the difference between mudjacking and foam lifting?
Both raise a settled slab by pumping material underneath it through drilled holes. Mudjacking uses a cement-based grout, while foam lifting uses an expanding polyurethane. Foam is much lighter, which some contractors prefer on soft ground, and usually needs smaller holes. Grout is heavier and has been used for a long time. A contractor can explain which they recommend and why.
Can cracks in my patio just be filled?
A crack that is thin and not moving can be cleaned out and sealed with a flexible product so rain and weeds stay out, and that slows the damage. Filling does not fix the reason the crack formed. If a crack keeps widening, one side is higher than the other, or pieces rock underfoot, the slab has a support problem that needs a different approach. A contractor can tell the two apart.
Will new concrete match my old driveway?
Not exactly, at least at first. New concrete is lighter and more even in color than slab that has weathered, and the difference usually softens only partly over time. Replacing whole panels between existing joints, or a full section up to a natural break, makes the change look deliberate. Decorative surfaces are the hardest to match, so plan the boundary with the contractor.
Why does the same spot keep sinking after repair?
Repeated sinking usually means the cause is still active: soft soil that keeps consolidating, a plumbing or drain leak washing material away, or runoff that saturates the ground at that spot. Fixing the source of the water, removing weak soil or rebuilding the base may be needed before any concrete repair will last. Share the history with the contractor at the visit.
Talk through your project
Start with the address, what you want poured or replaced, rough dimensions, and a few photos of the area and any existing concrete.
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