Concrete Slab Thickness Guide
Slab thickness depends on what will sit or drive on it. A thicker slab costs more but resists cracking under load — going thinner than recommended is the most common reason residential slabs fail early.
Recommended thickness by use
- Walkways and patios (foot traffic only): 4 in is standard.
- Driveways (passenger vehicles): 5–6 in, often with wire mesh or rebar reinforcement.
- Driveways carrying trucks or RVs: 6–8 in with reinforcement, on a well-compacted base.
- Footings: Sized by local building code based on load and frost depth — check with your building department rather than using a flat rule.
Estimating volume
Multiply length × width × thickness (in feet) to get cubic feet, then divide by 27 to get cubic yards. A 10 ft × 10 ft patio at 4 in thick needs about 1.23 yd³ before waste. Ready-mix trucks are typically ordered in quarter-yard increments, so round up accordingly and add 10% waste for spillage and uneven forms.
Base and reinforcement
A compacted gravel base under the slab improves drainage and reduces cracking from freeze-thaw movement — see the gravel driveway guide for base depth guidance. Reinforcement (wire mesh or rebar) is sized separately based on the slab's span and expected load.