4 Inch vs 6 Inch Concrete: When to Go Thicker

Use 4 inches for foot traffic (patios, sidewalks). Use 5-6 inches for vehicles (driveways, garage floors). That's the core rule. The extra thickness costs roughly $0.50-1.00 per square foot—worth it where needed, wasted money where it isn't.

Quick Decision Guide

Project	4 Inches	5-6 Inches
Patio	✓	—
Sidewalk	✓	—
Walkway	✓	—
Shed pad	✓	—
Driveway	—	✓
Garage floor	✓ (parking only)	✓ (workshop/lift)
Parking pad	—	✓
RV pad	—	✓ (6"+)

Simple version: Will vehicles drive on it? Use 5-6 inches. Foot traffic only? Use 4 inches.

When 4 Inches Is Right

4-inch concrete is appropriate when loads are limited to:

• People walking (150-250 lbs per person)
• Outdoor furniture (distributed across legs)
• Bicycles (~200 lbs with rider)
• Wheelbarrows (300-500 lbs loaded)
• Lawn equipment (push mowers, spreaders)

Projects That Should Be 4 Inches

Patios: Foot traffic only. Even heavy outdoor furniture distributes weight across multiple points. 4 inches has been the standard for decades because it works.

Sidewalks: Pedestrians, bikes, wheelbarrows—nothing that stresses 4-inch concrete.

Walkways: Same logic as sidewalks.

Shed pads: Light storage loads. Unless you're storing a vehicle or extremely heavy equipment, 4 inches is sufficient.

Garden borders and curbs: Decorative or light functional use.

See patio thickness guide for detailed patio specifications.

When 5-6 Inches Is Required

Vehicles change everything. A car weighs 3,000-5,000+ lbs concentrated on four tire contact patches. This creates:

• Point loading that thin concrete can't distribute
• Flexing as vehicles move across the slab
• Repeated stress from daily use
• Edge stress when tires track near slab edges

Projects That Need 5-6 Inches

Driveways: 5 inches minimum for passenger vehicles. 6 inches for trucks, SUVs, or if you want maximum durability. See driveway thickness guide.

Garage floors (heavy use): 4 inches works for basic parking, but workshops or car lifts need 5-6 inches.

Parking pads: Any area where vehicles will park regularly.

RV and boat storage: 6+ inches for heavy recreational vehicles.

Equipment pads: HVAC units, generators, or other heavy equipment.

The Cost Difference

Extra thickness isn't as expensive as you might think:

Thickness	Concrete per 100 sqft	Material Cost*
4 inches	1.23 cubic yards	~$185
5 inches	1.54 cubic yards	~$230
6 inches	1.85 cubic yards	~$280

*At $150/yard for ready-mix

Cost difference per 100 sqft:

• 4" to 5": ~$45 more
• 4" to 6": ~$95 more

Real Project Examples

10×20 Driveway section (200 sqft):

• 4 inches: $370 in concrete
• 6 inches: $555 in concrete
• Difference: $185

12×12 Patio (144 sqft):

• 4 inches: $265 in concrete
• 6 inches: $400 in concrete
• Difference: $135 (unnecessary expense for a patio)

20×24 Driveway (480 sqft):

• 4 inches: $890 in concrete
• 6 inches: $1,335 in concrete
• Difference: $445

That $445 buys 15-20 extra years of driveway life. The 4-inch driveway will likely need replacement in 10-15 years; the 6-inch driveway lasts 25-30 years.

For detailed cost breakdowns, see concrete cost per yard.

The Durability Difference

Thickness affects how long concrete lasts under stress:

Scenario	4-Inch Lifespan	6-Inch Lifespan
Patio (foot traffic)	25-30 years	25-30 years (no benefit)
Driveway (vehicles)	10-15 years	25-30 years
Garage (parking)	20-25 years	25-30 years
Garage (heavy use)	10-15 years	20-25 years

Why the difference?

Under vehicle loads, thin concrete flexes with each pass. This flexing creates micro-cracks that grow over time, especially with freeze-thaw cycles. Thicker concrete resists flexing, dramatically extending lifespan.

For foot traffic, the loads are too light to cause flexing—so extra thickness provides no durability benefit.

The 4-Inch Driveway Myth

Many homeowners (and some contractors) believe 4 inches is adequate for driveways because:

• "It meets code" (code is minimum, not optimal)
• "My neighbor has 4 inches" (and it's probably cracking)
• "Contractor said it's fine" (some cut corners to lower bids)

Reality: 4-inch driveways routinely fail within 10-15 years. The cracking pattern is predictable:

1. Edge cracks appear first (highest stress zone)
2. Cracks along tire paths develop
3. Cracks widen and multiply each freeze-thaw season
4. Sections begin to settle or break apart

By the time damage is obvious, the only fix is replacement.

Form Board Reference

Form boards determine slab thickness. Know what you're getting:

Lumber	Actual Dimension	Use For
2×4	3.5 inches	Too thin for most slabs
2×6	5.5 inches	Standard driveways
2×8	7.25 inches	Heavy-duty driveways

Watch for: Contractors using 2×4 forms for driveways. The resulting 3.5-inch slab is even thinner than the inadequate 4-inch standard.

Frequently Asked Questions

Is 4 inches enough for a driveway?

No. While 4 inches may meet building code minimums, it's inadequate for vehicle traffic. Expect significant cracking within 10-15 years. Use 5-6 inches for driveways—the extra cost is minimal compared to early replacement.

How much more does 6-inch concrete cost?

Approximately $0.95 more per square foot in concrete material (about 50% more). For a 400 sqft driveway, that's roughly $380 extra—a worthwhile investment for a driveway that lasts 25-30 years instead of 10-15.

Is thicker concrete always better?

No. Thicker concrete provides no benefit where loads are light. A 6-inch patio offers no advantage over a 4-inch patio for foot traffic—you're just spending more on concrete. Match thickness to actual use.

Key Takeaways

• 4 inches: Patios, sidewalks, walkways (foot traffic)
• 5-6 inches: Driveways, parking areas, heavy-use garages (vehicles)
• Cost difference: ~$0.50-1.00 per square foot
• Lifespan difference: 10-15 years (4" driveway) vs 25-30 years (6" driveway)
• Don't over-build patios or under-build driveways

Next Steps

• Calculate your project: Concrete Calculator
• Driveway estimates: Driveway Calculator
• Patio estimates: Patio Calculator
• Complete thickness guide: Thickness Guide
• All resources: Concrete Guides