Uneven Driveway? Here's What's Causing It and How to Level It

Why Your Driveway Is Uneven and How to Fix It

A driveway that was flat when it was poured does not always stay that way. Sections sink, edges heave, joints develop lips, and water starts pooling in areas that used to drain. Beyond being unsightly, an uneven driveway creates trip hazards, damages vehicles, and gets worse over time.

The fix depends on what is causing the unevenness. This guide walks through every common cause, how to identify which one you are dealing with, and the repair options from simplest to most comprehensive.

Common Causes of Uneven Driveways

1. Soil Settlement

What it looks like: Gradual, broad sinking — often affecting an entire section or one end of the driveway.

Why it happens: The soil beneath the driveway was not adequately compacted before construction, or fill material was placed without proper compaction. Over months or years, the soil compresses under the weight of the concrete and traffic, creating voids beneath the slab.

This is especially common in new construction where excavated soil was backfilled around foundations. The disturbed soil has not had time to consolidate naturally.

2. Erosion and Washout

What it looks like: Localized sinking, often near downspouts, slopes, or areas where water concentrates.

Why it happens: Water flowing beneath or alongside the driveway gradually washes away base material and soil. The voids left behind cause the slab above to settle. In Oregon's rainy climate, erosion is one of the most common causes of driveway settlement.

Key indicator: Settlement that worsens after heavy rain events, or settlement near gutter downspouts, roof drip lines, or slope transitions.

3. Clay Soil Shrink-Swell

What it looks like: Seasonal changes — the driveway may be more level in wet months and more uneven in dry months, or vice versa.

Why it happens: The Willamette Valley's clay soils expand significantly when saturated and shrink when dry. This cyclical volume change creates movement in the soil beneath the slab. Over many cycles, the soil structure breaks down and permanent settlement occurs.

4. Tree Root Heaving

What it looks like: A section lifts upward, creating a bump or ridge. The lifted area often follows a line pointing toward a nearby tree.

Why it happens: Tree roots growing beneath the slab push sections upward as the roots increase in diameter. Our detailed guide on tree root damage to driveways covers this cause and its solutions in depth.

5. Frost Heave

What it looks like: Sections lift upward, usually in winter, and may partially settle back in spring.

Why it happens: Water in the soil beneath the slab freezes and expands, pushing the slab upward. When it thaws, the slab settles back — but not always to its original position. Repeated cycles create permanent unevenness.

While less severe in the Willamette Valley than in colder regions, frost heave does occur during cold snaps, especially in areas with poor drainage where soil moisture is high.

6. Poor Original Construction

What it looks like: Uneven from the beginning or very early in the driveway's life. Sections at noticeably different grades, poor joints, inconsistent thickness.

Why it happens: Inadequate base preparation, insufficient compaction, inconsistent slab thickness, or improper grading during original construction. Unfortunately, the only way to fully correct construction defects is replacement.

How to Assess the Severity

Walk your driveway and measure the unevenness:

• Less than 1/2 inch difference: Minor. Primarily cosmetic. Grinding or do-nothing may be appropriate.
• 1/2 to 2 inches: Moderate. Creates trip hazards and drainage issues. Leveling is recommended.
• More than 2 inches: Significant. Indicates substantial base failure or void formation. Professional assessment needed.
• More than 4 inches: Severe. Replacement is typically more cost-effective than leveling.

Also check whether the unevenness is getting worse. Place a pencil or coin at a crack or joint and check it monthly. If the gap is growing, the underlying cause is active and ongoing.

Repair Options

Concrete Grinding

Best for: Minor lips and height differences at joints (less than 1 inch). Trip hazard removal.

A diamond grinding machine shaves down the high side of a joint or crack to create a smooth transition. This removes the trip hazard without addressing the underlying settlement.

Cost: $3-$8 per square foot of grinding area. Pros: Quick, inexpensive, no curing time. Cons: Only addresses the symptom. Does not raise settled sections. Grinding reduces slab thickness at the joint. Durability: Permanent for the ground area, but if settlement is ongoing, new lips will develop.

Mudjacking (Slab Jacking)

Best for: Settled sections with voids beneath, where the slab is intact and settlement is 1-3 inches.

Small holes (1.5-2 inches) are drilled through the slab. A cement-based slurry is pumped under pressure beneath the slab, filling voids and lifting the concrete to its original grade. The holes are patched after the slab is level.

Cost: $500-$1,500 per section (typically covers 50-150 sq ft per section). Pros: Non-destructive. Raises the slab back to grade. Much cheaper than replacement. Cons: Heavy slurry can cause additional settlement over time. Larger holes than foam. Requires 24-48 hours before vehicle traffic. Durability: 5-10 years. May need to be repeated if the underlying cause of settlement is not addressed.

Polyurethane Foam Leveling

Best for: Same applications as mudjacking, with better performance characteristics.

Similar to mudjacking but uses expanding polyurethane foam instead of cement slurry. Smaller injection holes (5/8 inch), lighter material, faster cure, and more precise control.

Cost: $800-$2,000 per section. Pros: Lightweight (does not add load to weak soil). Cures in 15 minutes. Smaller holes. Waterproof (does not erode). More precise leveling. Cons: More expensive than mudjacking. Not suitable for very large voids (foam expansion has limits). Durability: 8-15 years. Foam does not erode, degrade, or add settlement-causing weight.

Partial Slab Replacement

Best for: Sections that are broken, cracked apart, or have settled more than 3 inches. Areas where the base needs to be rebuilt.

The damaged section is saw-cut and removed. The base is excavated, repaired, and recompacted. New concrete is poured to match the surrounding grade. Dowel bars tie the new section to the existing slab.

Cost: $500-$2,500 per section. Pros: Addresses the root cause by rebuilding the base. Provides a 30+ year fix for the repaired area. Cons: New and old concrete will not match in color. Creates visible joints. More disruptive and time-consuming. Durability: 25-40 years with proper base preparation.

Full Driveway Replacement

Best for: Widespread settlement, base failure throughout, very old driveways, or when you want to correct grading, drainage, and appearance issues comprehensively.

Everything is removed and rebuilt from the subgrade up. This is the only option that addresses every issue simultaneously: base failure, drainage, thickness, grading, joints, and appearance.

Cost: $6-$10 per square foot for concrete, $3-$7 for asphalt. Pros: Complete solution. Addresses all underlying issues. New surface, new base, correct grades. Cons: Most expensive option. 3-7 days of construction. Full driveway closure. Durability: 30-50 years for concrete, 15-25 years for asphalt.

Decision Matrix

| Settlement Amount | Slab Condition | Base Condition | Recommended Fix | |---|---|---|---| | Less than 1/2 inch | Intact | Sound | Grinding or monitor | | 1/2 - 2 inches | Intact, minor cracks | Partially eroded | Foam leveling or mudjacking | | 1/2 - 2 inches | Cracked | Unknown | Professional assessment, likely partial replacement | | 2 - 4 inches | Intact | Voids present | Foam leveling (if voids are accessible) | | 2 - 4 inches | Cracked/broken | Failed | Partial or full replacement | | More than 4 inches | Any | Failed | Full replacement |

Preventing Future Settlement

Whatever repair you choose, address the cause to prevent recurrence:

1. Fix drainage. Redirect downspouts away from the driveway. Ensure the ground slopes away from the slab edges. Install drain channels if water flows across the driveway.
2. Maintain gutters and grading. Clogged gutters dump concentrated water next to the driveway. Eroded landscaping exposes slab edges to undermining.
3. Manage trees. If root heaving caused the problem, install root barriers and consider selective root pruning or tree removal.
4. Seal cracks promptly. Water entering through cracks erodes the base from above. Sealing cracks annually prevents this.
5. Proper base on new work. If replacing sections, insist on a minimum 6-8 inches of compacted aggregate base. On clay soils, use geotextile fabric between the subgrade and base.

Oregon-Specific Advice

Timing

• Level in spring or summer when the ground is at its driest and most stable.
• Avoid leveling in winter — saturated soils and active freeze-thaw make results less predictable.
• Fix drainage before leveling — otherwise the leveled slab will settle again.

Clay Soil Considerations

If your property sits on Willamette Valley clay, expect some seasonal movement. Foam leveling accommodates this better than mudjacking because the lightweight foam does not add load to already-weak soil. A 6-8 inch aggregate base during replacement isolates the slab from clay movement.

Insurance and Liability

Homeowner's insurance typically does not cover driveway settlement unless it is caused by a covered event (like a broken water main). However, if someone trips on your uneven driveway and is injured, you could be liable. Addressing trip hazards is a liability management priority.

Next Steps

Browse our services page to see concrete leveling and replacement options. View examples of completed leveling projects on our portfolio, or contact us for a free assessment of your uneven driveway.

For related reading, our guide on concrete slab repair vs. replacement helps you decide when leveling makes sense versus starting fresh.