What Is Concrete Flatwork?
Concrete flatwork is any horizontal concrete surface poured directly on the ground. Driveways, patios, sidewalks, garage floors, basement floors, and shed pads are all flatwork. The term comes from the construction industry to distinguish horizontal pours (flat) from vertical pours (walls, foundations, columns). If a contractor says they specialize in flatwork, they mean they pour and finish the surfaces you walk and drive on, not the structural elements that hold up buildings. Most residential concrete work is flatwork, which is why understanding the basics applies whether you are planning a driveway, a patio, or a simple shed pad.
Common Types of Residential Flatwork
| Type | Typical Size | Cost per Sq Ft | Key Spec |
|---|---|---|---|
| Driveways | 400 – 800 sq ft | $4 – $15 | 5–6 in. thick, 4,000 PSI, rebar reinforced |
| Patios | 100 – 400 sq ft | $6 – $15 | 4 in. thick, decorative finishes common |
| Sidewalks | 50 – 200 sq ft | $6 – $12 | 4 in. thick, broom finish for traction |
| Garage floors | 200 – 600 sq ft | $4 – $8 | 4–6 in. thick, vapor barrier underneath |
| Shed pads | 60 – 200 sq ft | $4 – $8 | 4 in. thick, gravel base, simplest flatwork project |
| Pool decks | 200 – 800 sq ft | $8 – $18 | 4 in. thick, slip-resistant or stamped finish |
Every type follows the same basic process: prepare the subgrade, build forms, place reinforcement, pour concrete, finish the surface, and cure. The differences are in thickness, mix strength, finish type, and reinforcement. A driveway needs heavier specs because it carries vehicles. A shed pad can use lighter specs because it only supports static weight. For project-specific guides, see our concrete driveway guides and concrete slab guides.
What Makes Good Flatwork (Every Type)
Whether you are pouring a driveway or a patio, the quality of any flatwork project depends on the same five factors. Cutting corners on any one of them leads to cracking, settling, or surface failure.
Subgrade preparation
Subgrade GuideThe ground underneath the slab must be compacted and level. Most flatwork requires 4 to 6 inches of compacted gravel as a base layer. Pouring concrete on uncompacted soil is the single most common cause of slab failure because the ground settles unevenly under the weight, creating stress cracks.
Proper thickness
Thickness Guide4 inches is the minimum for foot traffic (patios, sidewalks). Driveways need 5 to 6 inches to handle vehicle weight without cracking. Garage floors depend on whether you park passenger cars (4 inches) or heavy equipment (6 inches). Going thinner than spec to save money is false economy because thin slabs crack under load and cost more to replace than to pour correctly.
Right concrete mix
PSI GuideStandard flatwork uses 3,500 to 4,000 PSI concrete. Driveways and garage floors should use 4,000 PSI minimum because they carry repeated vehicle loads. Patios and sidewalks can use 3,500 PSI. In freeze-thaw climates, air-entrained concrete (5 to 7% air content) prevents surface scaling from salt and moisture cycles.
Control joints
Control Joints GuideConcrete shrinks as it cures, and it will crack. Control joints are cuts made every 8 to 12 feet that give the concrete a controlled place to crack, below the surface, where you cannot see it. Without them, cracks appear randomly across the surface. Every flatwork project needs them regardless of size.
Proper curing
Curing GuideConcrete does not dry, it cures through a chemical reaction that requires moisture. Letting the surface dry too quickly (especially in hot or windy weather) weakens the top layer and causes scaling, dusting, and premature cracking. Good flatwork contractors apply curing compound or wet-cure the surface for at least 7 days.
Flatwork vs. Structural Concrete: What Is the Difference?
| Factor | Flatwork | Structural Concrete |
|---|---|---|
| Orientation | Horizontal (flat on grade) | Vertical or elevated (walls, columns, elevated slabs) |
| Purpose | Walking, driving, or storage surface | Carries building loads (roof, floors, soil pressure) |
| Typical thickness | 4 – 6 inches | 8 – 24+ inches |
| Reinforcement | Wire mesh or light rebar | Heavy rebar, post-tension cables |
| Who does it | Flatwork contractors | Structural/foundation contractors |
| Permit required? | Sometimes (driveways, large patios) | Almost always |
This distinction matters when you are hiring. A contractor who specializes in flatwork has the tools and experience for finishing surfaces smooth and level. A structural contractor builds forms for walls and foundations. Some contractors do both, but many specialize in one or the other. Asking a structural crew to pour your patio, or a flatwork crew to pour your foundation, usually produces a worse result than hiring the right specialist.
Planning a Flatwork Project?
Whether it is a driveway, patio, or shed pad, submit the project to check for contractors whose listed flatwork specialties and service area fit the request.
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