In most cases, yes — you need a permit for a concrete slab if it will support a structure, exceed your jurisdiction’s size threshold, or sit close to a property line. Simple replacements of an existing sidewalk or driveway in the same material and location usually don’t. The rules are set locally, so the building department that covers your address is the final word, but three factors decide the answer almost everywhere: how big the slab is, what it holds up, and where it lands on the lot.
When a Permit Is Required
Size is the first trigger. Most jurisdictions exempt small slabs below a square-footage threshold, commonly 120 or 200 square feet. A backyard patio can cross that line faster than people expect once the full pour area is measured.
Intended use is the second. A slab that will act as a foundation — for a shed, garage, room addition, or any load-bearing structure — needs a permit regardless of size. The building department has to confirm the foundation meets structural and frost-depth requirements before anything is built on it.
Location is the third. Every lot has setback rules setting minimum distances between structures and property lines, and slabs generally count as structures for that purpose. A slab placed too close to a boundary can violate zoning even when it’s otherwise fine. Many jurisdictions also cap the share of a lot that can be covered by impervious surfaces like concrete to manage stormwater runoff, typically somewhere between 50 and 65 percent. Cross that cap and you’ll trigger a review or a separate stormwater permit.
When a Permit Isn’t Required
The International Residential Code, which forms the basis of building regulations in 48 states, exempts certain flatwork. Replacing an existing sidewalk or driveway in kind — same material, same size, same location — generally doesn’t require a permit. Other common exemptions include fences under seven feet, retaining walls under four feet measured from the bottom of the footing, and one-story detached accessory structures with a footprint under 200 square feet.
Local amendments can narrow these defaults, so a five-minute call to your building department before ordering concrete is worth it. And note one important distinction: even when a building permit isn’t required, a zoning permit might be. Some jurisdictions require zoning review for any new hardscape, patios included, to verify setback and impervious-surface compliance. A building permit confirms the work is structurally sound; a zoning permit confirms it’s in the right place.
Call 811 Before Any Digging
Whether or not your slab needs a permit, you’re required to call 811 before you break ground so underground utilities can be marked. Gas lines, electrical conduits, water mains, and telecommunications cables may run through your yard, and hitting one can cause injury, service outages, or liability for repair costs.
Call 811 or submit a request through your state’s one-call center website at least a few business days before you plan to dig. Locators mark the approximate path of buried utilities with paint or flags, usually at no charge. State laws set the notification windows and impose civil penalties for excavating without first requesting a locate — penalties that can reach several thousand dollars per violation, plus the cost of any damage.
What the Application Requires
Applications come from your local building department’s website or front counter. Forms vary, but most ask for the same core information:
- A project description covering the slab’s dimensions, thickness, intended use, and estimated cost. The estimate determines your permit fee, so a reasonable number matters.
- Property details, including your site address and, in most jurisdictions, the parcel identification number from your property tax records.
- A to-scale site plan showing property lines, existing structures, and the proposed slab’s placement with dimensions and distances from boundaries. This is how the reviewer confirms setback compliance.
- Technical specifications where applicable: concrete compressive strength, reinforcement details, and vapor barrier specs. Foundation slabs get more scrutiny than patios.
- Contractor information if you’re hiring one, including license number. Many jurisdictions let homeowners pull permits for their own work, though some limit that to owner-occupied properties.
The site plan is where most applications stall. Hand-drawn plans are acceptable in many jurisdictions if they’re reasonably to scale and show the measurements a reviewer needs. If you’re unsure what to include, ask the building department for a sample before you submit.
Fees, Review Times, and Inspections
Fees for a residential slab are usually modest. Many jurisdictions base them on estimated construction cost, using valuation data published by the International Code Council as a benchmark.1International Code Council. Building Valuation Data For a typical patio or shed slab, expect somewhere between $50 and a few hundred dollars depending on project size and local fee schedule. Some departments charge a flat fee for small projects.
After you submit, the department runs a plan review against building codes and zoning. For straightforward residential projects, review generally takes one to two weeks. If the reviewer flags issues, you get a corrections list and the clock resets on resubmission. Build that into your schedule, especially if a contractor is already lined up.
Once approved and paid, you’ll receive a permit card that has to be posted at the site in a visible location. A slab permit typically triggers two inspections. The pre-pour inspection happens after forms, reinforcement, gravel base, and vapor barrier are in place but before any concrete goes down; the inspector verifies subgrade preparation and reinforcement match the approved plans. The final inspection, after the concrete has cured, closes out the permit.
Do not pour before the pre-pour inspection. If you skip it, the inspector has no way to verify what’s under the slab, and the department can require you to remove the concrete so they can see the subgrade.
Consequences of Skipping the Permit
Pouring without a required permit rarely saves money once things unravel. The immediate risk is a stop-work order: if an inspector discovers unpermitted construction, work stops until the situation is resolved, leaving you with a half-finished project and an idle contractor. Fines follow. Some jurisdictions charge a flat penalty; others double or triple the original permit fee for after-the-fact applications, and daily fines for ongoing violations are common.
The longer-term consequences are worse. If the finished slab doesn’t meet code — setback violations especially — the department can order you to tear it out at your own expense, and you’ll still owe the fines. Retroactive permits are sometimes available, but the department isn’t obligated to approve work that wouldn’t have passed review in the first place.
Unpermitted work also surfaces years later. Homeowner’s insurance claims tied to unpermitted construction can be denied if the insurer determines the work wasn’t up to code or was never inspected. And most states require you to disclose known unpermitted work when you sell. Failing to disclose can expose you to a lawsuit from the buyer after closing, even if you weren’t the one who did the work. Buyers and their lenders check permit records, and a slab without a matching permit raises flags during due diligence.
HOA Approval Is a Separate Step
If you live in a community with a homeowners’ association, a government building permit and HOA approval are independent requirements. Getting one does not satisfy the other, and you need both before starting work.
Your HOA’s covenants, conditions, and restrictions — the CC&Rs — are a private contract governing what you can do with your property’s exterior. These rules often regulate the size, placement, materials, and finish of patios and other hardscape. The architectural review committee typically requires a separate application with drawings and material samples.
Skipping HOA review can result in fines from the association and a demand to remove the slab, even with a valid building permit. Because the aesthetic requirements may shape your design, review your governing documents early — before you finalize plans, not after.
How To Confirm Your Local Requirements
Slab permits are governed at the city or county level, so the most useful step is contacting your local building department directly. Search for your city or county name plus “building department” or “permit office” to find the right site. Most departments publish applications, fee schedules, and exemption lists online.
If the website isn’t clear about your specific project, call or visit. Staff field these questions daily and can usually give a definitive answer in a few minutes based on the slab’s size, location, and purpose. Some departments offer a free preliminary consultation where a plan reviewer will look at your proposal informally before a formal submission — a service worth using if it’s available, because it can save you a rejected application and weeks of delay.