Driveways and patios sit directly on soil, and when that soil loses its support, the slabs above it sink. Concrete raising corrects this by lifting the settled slab back to grade without removing it. One widely used form of this work involves injecting polyurethane foam beneath the concrete. This article explains why driveways and patios settle, how polyjacking fits into the repair options, what the process involves, and where the method has limits.
Why Driveways and Patios Settle
A slab depends on the soil below it for nearly all of its support. When that soil washes away, compresses, or shifts, the slab drops into the space left behind. Several conditions cause this.
Water and Soil Erosion
Water is the most common cause. Rain runoff, leaking pipes, and downspouts that empty near the slab can carry fine soil away from the base. Voids form slowly, and the slab eventually settles into them. Settlement often appears first at edges, joints, and corners, where water enters most easily.
Compaction, Roots, and Soil Movement
Soil that was not compacted properly during construction can keep settling for years after the concrete is poured. Clay soils swell when wet and shrink when dry, which moves the ground with the seasons. Tree roots can also disturb the base, either by pushing upward or by leaving voids as they decay.
How Driveway and Patio Settlement Differs
Driveways carry the weight of vehicles, so a settled slab can worsen when cars and trucks cross it. Long driveways often have many joints, and each joint can drop at a different rate. Patios usually sit next to the house, and a patio that slopes toward the foundation can send water toward the structure. In both cases, uneven edges create tripping hazards and allow water to collect.
Signs a Driveway or Patio May Need Lifting
Several visible conditions suggest a slab has settled:
- Slabs that sit at different heights along a joint
- A patio or driveway that slopes toward the house
- Water that collects on the surface after rain
- Raised edges that catch shoes, tires, or equipment
- A hollow sound when the slab is tapped, which can point to a void below
These signs show that something has moved, but they do not identify the cause, so an assessment of the soil and drainage usually comes first.
How Concrete Raising Works
The method relies on a simple principle. Material is pumped into the void beneath the slab, and the pressure of that material pushes the slab upward. Small holes are drilled through the concrete, and a hose delivers the material in measured amounts. The crew checks the slab with levels while it rises and stops when it meets the adjoining surfaces. Two materials are common.
Polyjacking
Polyjacking uses polyurethane foam made from two liquid components that expand after injection. The foam fills voids, hardens within minutes, and weighs less than cement slurry. Lighter weight matters where the soil is soft and could compress under added load. The holes are small, and the surface is usually ready for use soon after the work ends.
Cement Slurry
Mudjacking uses a mixture of cement, water, and soil or sand. The slurry is heavy and fills large voids well. The holes are typically larger than those used for foam, and the mixture needs time to cure before the surface carries traffic.
What Polyjacking Services Include
Work of this kind generally follows a set sequence from assessment to cleanup.
- Inspection. The crew measures the height difference, checks for cracks, and identifies the likely cause of settlement.
- Drilling. Small holes are drilled in a pattern across the sunken slab.
- Injection. Foam is delivered through the holes in controlled amounts while the slab is monitored.
- Adjustment. The crew checks the slab with levels and stops when it aligns with adjoining concrete.
- Finishing. The holes are patched, and excess material is cleaned from the surface.
Most residential projects take a few hours, and foam is often ready for use soon after injection, though timing varies with slab size and weather.
Benefits Compared With Replacement
Replacing a slab means breaking out the old concrete, removing debris, rebuilding the base, pouring new concrete, and waiting for it to cure. Lifting avoids most of those steps. The work often finishes in hours, produces less waste, and keeps the existing finish and color. Landscaping and nearby structures are also less disturbed. Lifting does not repair cracks, but it corrects the settlement that often causes cracks to widen.
Limits and Conditions That Affect Results
The method does not suit every slab. Concrete that is crumbling, heavily cracked, or broken into many pieces may not rise as one unit and may need replacement. Surface damage such as scaling requires a separate repair. If water continues to wash soil away, the slab can settle again after lifting, so drainage problems need correction as well. Lifting too fast can crack a slab, which is why controlled injection and constant level checks are standard practice.
Questions to Ask a Provider
Owners who decide on lifting usually need to select a provider. Useful questions include why the slab sank, which material is recommended, and how the crew will control the lift. Owners can also ask for proof of licensing and insurance, a written scope of work, and the terms of the warranty. Comparing answers from more than one provider makes differences in process and materials easier to see.
Lift It Pro as an Example
Businesses such as Lift It Pro offer concrete lifting for residential properties, and an owner reviewing any provider of polyjacking services can apply the same questions. Useful topics include the assessment method, the materials used, the expected timeline, and the drainage advice that comes with the repair. Examples of completed driveway and patio projects can also show what results to expect.
Conclusion
Driveways and patios settle when the soil beneath them loses support, and lifting restores the slabs by filling voids and pushing the concrete back to grade. Foam and cement slurry each have a place, depending on soil conditions, slab size, and the amount of lift needed. Owners who understand the causes, the process, and the limits can judge whether lifting suits their concrete and plan for the drainage conditions that affect how long the repair lasts.