Slab lifting in Miami: foam, grout, or replace

Concrete slabs on grade drop for one reason: the ground under them went away. In Miami-Dade that almost always means water moved it, either from a leaking supply line, a broken drain, stormwater with nowhere to go, or tidal cycling through a failed seawall. The slab itself is usually fine. It is spanning a hole, and eventually it cracks or tilts into it.

First: find out why

Lifting a slab over an active leak is buying time at full price. Before anything is injected, the sensible sequence is to establish where the water came from: a meter test for a supply leak, a camera for a drain, a walk of the roof water and the surface grade after rain, an inspection of the seawall if the property is on water. Sometimes the answer is obvious, an irrigation line running under the driveway. Sometimes it takes an afternoon. It is still cheaper than doing the lift twice.

The second preliminary is mapping the void. Tapping the slab across its area tells you where it is hollow, and shooting elevations tells you how far it has dropped and in which direction. Together they set the injection pattern. A pattern chosen without them is guesswork with a machine attached.

Polyurethane foam injection

Two liquid components are pumped through ports of about 5/8 inch drilled through the slab. They react on contact, expand, fill the void, and lift the slab. The reaction is fast, reaching load-bearing strength in roughly fifteen minutes.

• Weight. The decisive advantage in Miami. Foam is a fraction of the weight of the equivalent volume of cementitious grout. Adding several tons of material to ground that already failed to support a slab is a poor plan, and this avoids it.
• Speed. Most residential jobs are a single day, and the surface is back in service the same afternoon.
• Water. Cured polyurethane does not wash out, which matters where the void formed because water was moving through.
• Precision. Lifting is controlled to a fraction of an inch, monitored with a laser as it happens.
• Cost. Higher per hole than grout, but fewer holes are needed. A driveway or walkway section commonly runs $1,400 to $2,500; a pool deck or large patio $3,500 to $6,500.

Cementitious grout, or mudjacking

The older method. A slurry of cement, sand, and sometimes fly ash is pumped through larger holes, typically an inch and a half to two inches, filling the void and raising the slab hydraulically.

• Cheaper per cubic foot. Genuinely so, which keeps it competitive on very large voids.
• Heavy. The problem in this county. On competent ground the added load is irrelevant. Over soft fill or organic soil it is not.
• Slower. Cure before loading is typically 24 to 48 hours.
• Larger holes. More visible patches, and more of them.
• Erodible. Where water is still moving through the ground, a cementitious fill can be washed out over time in a way cured polyurethane is not.

None of that makes it wrong. It makes it a method with a narrower window: large void, competent surrounding ground, cost-sensitive, appearance underneath irrelevant.

Replacement

Sometimes the right answer. A slab that has broken into many small pieces cannot be lifted as a unit, because there is no unit. Neither can one that has been patched repeatedly, that is heavily spalled, or that is thin and under-reinforced enough that lifting would simply crack it in new places.

The rough test is panel size. If the slab has dropped as one or two large pieces with clean joints, it lifts. If it is a mosaic, it goes. And where replacement is the answer, the void underneath still has to be dealt with first, or the new slab starts the same journey.

Interior slabs

Lifting an interior floor is the same operation with an access problem attached. Ports have to be cored through whatever the finished floor is and then patched, which is why interior work carries a premium of roughly $1,200 to $4,500 on top of the lift itself. Tile is the awkward case: matching a discontinued tile is often impossible, so the practical approach is to core through grout lines and sacrificial tiles where spares exist, and to have that conversation before the drill comes out.

What lifting does not fix

A slab lift addresses the slab. If the house itself has settled, if a footing has moved, if walls are cracking in a pattern, that is a different scope, and lifting a patio will not touch it. The two do sometimes share a cause, which is a good reason to shoot elevations inside the house while somebody is already on site with the equipment. The settlement conversation is in underpinning methods, and the full scope detail for this work is on the slab leveling page.

Get a free quote

Call (786) 841-1091 or send the quote form. Describing what you are seeing costs nothing, and so does the written quote that follows.