Garage Slabs and Concrete Foundations in Chicago
Two Chicago cost models put a garage floor or slab foundation at $6.80–$14 per square foot. A new floor for a detached garage off an alley also comes with its own permit path and a truck-access question. Our vetted local pro can check access and tell you what the slab needs.
Typical price in Chicago: Garage floor or slab foundation, installed$6.80–$14 per sq ftSource: 2 Chicago cost models, price data from September 17, 2026
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- Price ranges from sourced dataUpdated September 17, 2026
- 4towns covered in Chicago
Reviewed by: Patrik Lorentzson, Editor, Chicago Prime Concrete · Last reviewed
General information only, not advice for your project. Chicago Prime Concrete does not advise on, design or manage projects; the contractor you choose does.
How much does a garage slab cost?
A 400–600 square foot garage floor runs $4,000–$8,400, or $8–$14 per square foot, in one Chicago cost model. Another, built from state highway bid data with a residential adjustment, puts a slab foundation at $6.8–$10.45 per square foot. Both are models rather than contractor quotes, so treat them as a budget check. More in the Chicago concrete price guide.
What permit does a new detached garage need?
Usually the city's express permit, for a detached garage of up to 600 square feet on a slab. Chicago's Express Permit Program covers building or replacing a residential garage of up to 600 square feet on a concrete slab-on-grade foundation, with wood or light-gauge metal framing. The application lists a licensed general contractor (Class A to E) and a licensed electrical contractor among the required contractors, although an owner may act as general contractor in some cases. The permit guide covers the rest.
Does the concrete company need a mason license?
Not for this kind of slab. The city says a mason contractor license isn't required to install or repair slab-on-grade foundations for single-story non-occupiable structures such as sheds and private garages, or for concrete paving and sidewalks. Foundations that are part of a house are different: masonry work on buildings needs a licensed mason contractor, and Class C covers site-formed concrete. Anything structural belongs with the engineer or architect on the permit.
What if the only access is the alley?
Expect to pay $400–$800 more if the truck can't reach the slab. Tight alley clearances can keep a standard ready-mix truck from getting close, so the pour needs a concrete pump at $400–$800 extra or smaller loads with short-load surcharges. Ask the pro how the concrete will reach the slab. The garage slab questions page covers vapor barriers and cracks.
Sources
- ConstructlyTools: concrete slab cost in Chicago (2026 cost model), September 17, 2026
- SlabCalc: concrete foundation cost, Chicago (model from IDOT bid data, May 2026), September 17, 2026
- Chicago Department of Buildings: Express Permit for a detached frame garage, September 17, 2026
- Chicago Department of Buildings: mason contractor license, September 17, 2026
- Chicago Department of Buildings: Express Permit for masonry and concrete repair, September 17, 2026
- Chicago Department of Buildings: does my project require a licensed general contractor?, September 17, 2026
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Frequently asked questions
Does a basement floor or attached garage count as a simple slab?
No. Reconfiguring concrete building elements, such as lowering a basement floor slab, needs drawings from an Illinois-licensed architect or structural engineer under the city's masonry express permit, as does concrete repair over 100 square feet.
Can I pour a shed pad without a general contractor license?
Yes, at your own home, within limits. An individual may act as general contractor for work at their own primary residence if the property has no more than 6 units and no building taller than 3 stories, for one property per calendar year. A company doing the work for pay is a different matter; see the hiring guide.