Concrete Slab Cost: Foundation, Garage, and Utility Slabs

How Much Does a Concrete Slab Cost?

Concrete slabs are the workhorses of construction, providing flat, durable surfaces for everything from home foundations to garage floors to HVAC equipment pads. Understanding slab costs helps you budget accurately whether you are building new construction, adding a shop, or pouring a simple utility pad.

Here is what concrete slabs cost in 2026:

| Slab Type | Thickness | Cost Per Sq Ft | Example Size & Cost | |---|---|---|---| | Utility pad (AC, generator) | 4 inches | $6 - $10 | 4x4 ft: $150 - $250 | | Shed or outbuilding pad | 4 inches | $5 - $9 | 10x12 ft: $700 - $1,200 | | Patio slab | 4 inches | $6 - $12 | 12x16 ft: $1,200 - $2,500 | | Garage floor (2-car) | 4-5 inches | $7 - $12 | 20x24 ft: $3,500 - $6,000 | | Workshop / barn floor | 5-6 inches | $8 - $14 | 24x36 ft: $7,000 - $12,000 | | Residential foundation | 4-6 inches | $8 - $15 | 1,500 sq ft: $12,000 - $22,500 | | Commercial foundation | 6-8+ inches | $10 - $18 | Varies widely |

Concrete Slab Cost Breakdown

Materials (40-50% of Total)

Concrete: Ready-mix concrete in Oregon costs $130 to $170 per cubic yard delivered. One cubic yard covers approximately 80 square feet at 4 inches thick. For a 500-square-foot garage slab at 5 inches thick, you will need roughly 8 cubic yards of concrete ($1,040-$1,360 in material alone).

Aggregate base: Compacted gravel beneath the slab typically costs $25-$45 per ton, installed. A standard 4-inch base requires about 0.6 tons per 10 square feet.

Reinforcement: Wire mesh runs $0.40-$0.80 per square foot. Rebar (typically #4 rebar on 18-inch centers) costs $0.75-$1.50 per square foot including placement.

Vapor barrier: A 10-mil polyethylene vapor barrier beneath the slab costs $0.10-$0.25 per square foot. Required by code for habitable spaces and recommended for garages and workshops.

Forms: Lumber for forming is a relatively small cost ($200-$600 for most residential projects) but necessary for clean, straight edges.

Labor (45-55% of Total)

Labor is the largest cost component for concrete work. Forming, pouring, screeding, floating, finishing, and cleanup require skilled crews and are time-intensive. Labor rates in Oregon range from $40 to $70 per hour per worker, with a typical residential slab requiring a crew of 3-5 people for 1-2 days.

Equipment (5-10% of Total)

Equipment costs include:

• Concrete pump (if truck cannot reach the pour site): $300-$1,000 per pour
• Power trowel / finishing equipment: Typically included in labor pricing
• Excavation equipment (if grading is needed): $150-$300 per hour

Slab Types in Detail

Foundation Slabs

A foundation slab (also called a slab-on-grade foundation) serves as both the structural foundation and the floor of a building. This is the most common residential foundation type in Oregon outside of hillside construction.

What makes foundation slabs different:

• Thickened edges: The slab perimeter is thickened to 12-18 inches to serve as the footing, adding structural capacity where walls bear on the slab.
• Reinforcement: Code requires rebar in foundation slabs, typically #4 rebar on 12-18 inch centers in both directions, with additional reinforcement at thickened edges.
• Vapor barrier: Required by Oregon building code for habitable spaces. A 10-mil or 15-mil poly sheet beneath the slab prevents moisture migration through the concrete.
• Insulation: Energy code in Oregon may require rigid foam insulation beneath or around foundation slabs, depending on the climate zone and building type. Adds $1-$3 per square foot.
• Plumbing and utility rough-in: Drain pipes, water lines, and electrical conduits must be placed before the pour. Coordination with other trades is essential.

Cost: $8-$15 per square foot for the slab itself, not including the utilities embedded in it.

Garage Slabs

Garage slabs need to handle vehicle weight, resist oil and chemical stains, and provide a level surface for parking and working.

Key specifications:

• Thickness: 4 inches minimum for passenger vehicles; 5-6 inches if you will park trucks, RVs, or heavy equipment
• Reinforcement: Wire mesh minimum; rebar recommended for heavy-use garages
• Floor slope: Slight slope toward the door (1/8 inch per foot) for drainage
• Control joints: Every 8-10 feet to control cracking
• Finish: Broom finish for traction, or trowel finish if you plan to apply epoxy coating later

Typical cost for a 2-car garage (20x24 ft = 480 sq ft): $3,500-$6,000 including base prep, forming, pouring, and finishing. Three-car garages (20x36 ft) run $5,000-$9,000.

Workshop and Barn Slabs

Workshop and barn floors see heavier use than typical garages and may need to support equipment, vehicles, or heavy storage.

Key specifications:

• Thickness: 5-6 inches for light workshop use; 6-8 inches for heavy equipment
• Reinforcement: Rebar grid (#4 on 12-18 inch centers) for heavy loads
• Joints: Control joints every 10-12 feet; isolation joints around equipment pads
• Floor drains: Built-in drains are common in workshops and barns. Add $300-$800 per drain.
• Finish: Power-troweled for a smooth, easy-to-clean surface; apply hardener or epoxy for chemical resistance

Typical cost for a 24x36 ft workshop (864 sq ft): $7,000-$12,000.

Utility and Equipment Pads

Small concrete pads for HVAC units, generators, hot tubs, and other equipment are straightforward projects with relatively low costs.

Typical pad sizes and costs:

| Equipment | Pad Size | Cost | |---|---|---| | AC condenser | 3x3 ft or 4x4 ft | $150 - $350 | | Generator | 4x4 ft or 4x6 ft | $250 - $500 | | Hot tub | 8x8 ft to 10x10 ft | $600 - $1,500 | | Garbage can enclosure | 4x8 ft | $300 - $600 | | Shed pad | 8x10 ft to 12x16 ft | $500 - $1,500 |

Equipment pads are typically 4 inches thick with wire mesh reinforcement. Hot tub pads should be 5-6 inches with rebar to handle the significant weight (a filled hot tub can weigh 3,000-5,000+ pounds).

Oregon Building Codes and Permits

When Permits Are Required

In most Oregon jurisdictions, permits are required for:

• Foundation slabs: Always require a building permit and inspections
• Garage additions: Require a building permit if attached to a structure or if the garage is a new structure
• Slabs over a certain size: Some jurisdictions require permits for slabs over 120 or 200 square feet
• Utility pads: Generally exempt from permits unless electrical or plumbing connections are involved

Permit costs in Oregon range from $75 to $500+ depending on the project scope and jurisdiction.

Inspections

Foundation and structural slabs require multiple inspections:

1. Footing inspection: Before pouring, the inspector verifies excavation depth, reinforcement placement, and soil conditions
2. Pre-pour inspection: After forms, reinforcement, and utilities are in place
3. Final inspection: After the slab is poured and cured

Scheduling inspections adds 1-3 days to your project timeline. Your contractor should coordinate all inspections.

Reducing Concrete Slab Costs

Right-Size Your Slab

Do not over-specify thickness or reinforcement beyond what your application requires. A utility pad does not need the same specs as a structural foundation. Consult with your contractor about the appropriate design for your specific use.

Prepare the Site Yourself

If your site needs clearing, grading, or old structure removal, doing this work yourself (or hiring a separate contractor) before the concrete crew arrives can save on hourly equipment charges. However, final grading and compaction should be done by the concrete contractor to ensure proper base preparation.

Combine Projects

If you need multiple slabs (garage + patio + utility pad), having them all done in a single mobilization saves 10-20% compared to separate projects. The concrete truck delivery and crew setup are fixed costs that get spread across more work.

Choose the Right Finish

A standard broom finish is included in base pricing. Decorative finishes (stamped, colored, exposed aggregate) add $3-$12 per square foot. For utility slabs that will not be visible, skip the decorative work and save the budget for areas that matter aesthetically.

Get a Free Slab Estimate

Whether you need a simple equipment pad or a full building foundation, Cojo provides free estimates for concrete slab projects across Oregon. We will assess your site, discuss specifications, and provide clear, detailed pricing.

Contact us for your free estimate or learn about our full range of services. See examples of our concrete work in our project gallery.