Concrete Slab Cost

A concrete slab is the flat, poured base under a patio, shed, garage, workshop or house addition. Contractors price it by the square foot of surface, with thickness and reinforcement folded in. LawnStarter puts the national average at $6.60 per square foot installed, with a typical range of $4.34 to $7.73. Inch Calculator splits the bill roughly evenly: $2 to $5 per square foot for materials and another $2 to $5 for labor.

Cost by slab size

Averages: LawnStarter, at $6.60 per sq ft. Ranges apply LawnStarter's $4.34–$7.73 per sq ft range to each area.

Inch Calculator, using its $4 to $8 combined range, puts a 30' x 30' slab at $3,600 to $7,200. For a quick estimate, multiply length by width in feet, then by your local price per square foot. Small slabs often cost more per foot than the table suggests, because many contractors have a minimum charge for mobilizing a crew and a truck.

Cost by thickness

Thicker slabs use more concrete and carry heavier loads. LawnStarter's average installed prices by thickness:

Four inches is the standard for most residential slabs. Going from 4 to 6 inches adds 50% more concrete, which is why the per-foot price climbs. Local code or your engineer may require a specific thickness for a garage or a living space.

Cost by project type

Source: LawnStarter.

A slab for a home addition or a slab-on-grade house foundation is a larger, engineered job with footings, plumbing rough-ins and inspections, and is priced separately from a simple flatwork slab.

What goes into the price

Concrete. Ready-mix concrete delivered by truck costs about $125 to $165 per cubic yard, according to Inch Calculator. One cubic yard covers about 81 square feet at 4 inches thick, so a 20' x 20' slab needs about 5 cubic yards before waste. Contractors typically order 5% to 10% extra. Very small jobs may be mixed on site from bags instead.

Site preparation. The ground has to be cleared, leveled and compacted, then topped with a gravel base. Sloped yards, tree roots or poor soil add excavation and fill. Forms are set around the edges to hold the wet concrete.

Reinforcement. Steel keeps cracks from spreading. Inch Calculator lists wire mesh at $0.20 to $0.30 per square foot for the material and rebar at $2 to $3 per square foot installed; LawnStarter adds about $0.35 per square foot for wire mesh.

Labor. Pouring, screeding, floating, finishing and cutting control joints are skilled work that has to be done within a short window before the concrete sets. The crew size and hours depend on the slab size and access for the truck.

Add-ons and upgrades

Source: LawnStarter.

A vapor barrier matters under any slab that will be enclosed, such as a garage, workshop or room, because it keeps ground moisture from wicking up into flooring. Thickened edges strengthen the perimeter where loads concentrate, and are common under shed and garage walls. Insulation is worth adding under a heated space.

Decorative finishes

A plain broom finish is included in the base price. Decorative finishes are added on top (LawnStarter, per sq ft):

Stamped concrete is the most popular upgrade for patios because it imitates stone or brick at a lower price than real pavers. Epoxy is the usual choice for garage floors. Polished and stained concrete are common for basements, shops and modern interiors.

Concrete slab vs. pavers and asphalt

Concrete is usually the cheapest permanent hard surface for a patio or shed base. Pavers cost more up front but individual pieces can be replaced if one cracks or settles; see our paver patio cost guide. For driveways, asphalt is typically cheaper per square foot but needs resealing every few years; compare in our asphalt driveway cost guide.

Can you pour a slab yourself?

A small shed pad or walkway can be a DIY job if you are comfortable with forms, mixing and finishing. Bagged concrete makes sense up to a cubic yard or so; beyond that, a ready-mix delivery is easier, but you will need several helpers ready to place and finish the concrete before it sets. Large slabs, garage floors and anything that will carry a structure are better left to a contractor, who brings the equipment, knows local code and can deal with problems such as soft soil and drainage. Mistakes in concrete are hard and expensive to fix: a slab that cracks or slopes the wrong way usually has to be broken up and poured again.

Questions to ask contractors

1. What thickness and what reinforcement are included?
2. Is the gravel base, compaction and forming in the price?
3. Is a vapor barrier included where needed?
4. Where will control joints be cut, and how soon after the pour?
5. Who handles the permit, and is removal of old concrete or soil extra?
6. How long should the slab cure before it is used, and is there a warranty on cracking?

Sources

1. LawnStarter: How Much Does a Concrete Slab Cost in 2026? (by Jane Purnell, updated Dec 11, 2024)
2. Inch Calculator: Concrete Slab Cost Guide