How Much Does a Concrete Slab Cost?

Concrete Slab Cost: Everything You Need to Know

Whether you're adding a shed foundation, building an outdoor workshop, extending a patio, or preparing for an addition, a concrete slab is often the most cost-effective foundation choice. In 2026, basic concrete slab installation costs $4–$8 per square foot, including materials and labor. That means a common 20x20 slab (400 sq ft) runs approximately $1,600–$3,200.

Concrete Slab Prices by Common Size

• 10x10 slab (100 sq ft): $600–$1,000
• 12x12 slab (144 sq ft): $750–$1,400
• 16x16 slab (256 sq ft): $1,100–$2,100
• 20x20 slab (400 sq ft): $1,600–$3,200
• 24x24 slab (576 sq ft): $2,400–$4,600
• 30x30 slab (900 sq ft): $3,800–$7,200

Slab Cost Factors

Thickness

This is one of the biggest cost drivers. Standard thicknesses and their uses:

• 4 inches: Sheds, light storage, patios — $4–$6/sq ft
• 5 inches: Garages with passenger vehicles — $5–$7/sq ft
• 6 inches: Heavy trucks, workshops, RV pads — $6–$9/sq ft
• 8+ inches: Commercial loads, structural applications — $9–$14/sq ft

Reinforcement

Wire mesh (welded wire reinforcement) is standard and adds $0.25–$0.50/sq ft. Rebar provides superior crack resistance and is recommended for vehicle slabs, heavier loads, or expansive soils — adds $0.75–$1.50/sq ft. Fiber-reinforced concrete (synthetic fibers mixed into the concrete) is sometimes used instead of or in addition to steel.

Sub-Base Preparation

A proper slab needs 4–6 inches of compacted crushed stone base. This material and labor typically adds $0.50–$2/sq ft. In regions with expansive clay or soft soils, a proper base is especially critical — it prevents the settling and cracking that leads to premature slab failure.

Vapor Barrier

For slabs in garages or enclosed structures, a plastic vapor barrier beneath the concrete prevents moisture migration from the ground. This adds $0.10–$0.30/sq ft — a small cost with significant impact on moisture control and concrete longevity.

Concrete Mix and Strength

Residential slabs typically specify 3,000 PSI or 4,000 PSI concrete. Higher-strength mixes cost more but provide better durability for high-load applications. Air-entrained concrete (for freeze-thaw climates) is standard in northern states. Your contractor should specify the appropriate mix — find a slab contractor near you who understands local soil and climate conditions.

Specialty Slab Types and Their Costs

Garage Slab

A standard two-car garage slab (24x24 = 576 sq ft) at 5-inch thickness with rebar runs approximately $3,000–$6,000. Costs vary by region — Florida and southern states tend toward the lower end; the Northeast and Pacific Coast toward the higher end.

House Foundation Slab

A monolithic slab foundation for a full house is a major project. Costs depend on home size, local code requirements, and soil conditions. Expect $5–$15/sq ft for a residential foundation slab, meaning a 1,500 sq ft home might have an $8,000–$22,000 slab foundation cost. See our detailed guide on concrete foundation costs for more information.

Equipment Pad

HVAC equipment pads (3x3 to 5x5) are small slabs that cost $200–$600 typically. Generator pads, hot tub pads, and similar small concrete work can often be completed in half a day by an experienced crew.

Pouring Concrete in Different Climates

Concrete placement is weather-sensitive. In cold climates (below 40°F), special precautions are required — blankets, heaters, and heated mix water add cost. In very hot climates, rapid drying can cause cracking if the pour isn't properly managed. Both scenarios may add 5–15% to project cost during extreme weather seasons.

Getting an Accurate Quote

When getting quotes for a concrete slab, make sure each contractor specifies:

• Slab dimensions and thickness
• Concrete PSI strength and type
• Reinforcement type (mesh, rebar, fibers)
• Sub-base depth and material
• Whether vapor barrier is included
• Any excavation required

Browse concrete slab contractors on ConcreteListings to find local professionals who provide detailed, transparent quotes.