In most cases, yes — you do need a permit for a concrete slab in your backyard, though small patio slabs at ground level are often exempt in jurisdictions that follow the International Building Code. The answer turns on three things: how big the slab is, what it will hold up, and where it sits on your lot. A slab that’s permit-free in one city can require full plan review in the next one over, so the only reliable answer comes from your local building department.
What Pushes a Slab Into Permit Territory
Size is the first filter. Many jurisdictions exempt slabs below a set square footage, commonly 100 or 200 square feet, as long as the slab sits at or near existing grade. The model International Building Code exempts replacement-in-kind of existing patios, driveways, and sidewalks from building permits. A brand-new slab is treated differently, and your local code may follow the model closely or depart from it.
What the slab supports matters more than the slab itself. A flat pad for a table and chairs is the simplest case and the most likely to be exempt. A slab acting as a foundation for a shed, detached garage, or accessory dwelling unit triggers structural review that goes well beyond flatwork. Even a hot tub pad can pull you into permit territory because of the concentrated weight.
Changing the grade of the yard is a third trigger, and it catches people off guard. If you need to excavate more than a few inches or build up soil to level the site, some jurisdictions require a separate grading permit so you aren’t redirecting stormwater onto a neighbor’s property. The building permit and the grading permit are two different approvals, and a project can need both.
Zoning Rules Apply Even When a Building Permit Doesn’t
A slab small enough to skip a building permit still has to obey zoning. Most residential zones require improvements to stay a minimum distance from property lines. Setback distances vary by zoning district and sometimes by the type of improvement: a patio might have a smaller required setback than a roofed structure, or the same one. The only way to know is to check your property’s specific zoning designation.
Easements add another layer. Utility, drainage, and access easements can cut across a yard in places that aren’t obvious from the surface. Pouring concrete over a utility easement can force you to remove the slab later if the utility company needs access. Your deed or survey plat shows recorded easements, and the local planning office can usually pull them up by address.
Impervious surface caps are the third zoning issue. A concrete slab adds impervious area, meaning rainwater runs off instead of soaking in. Most municipalities cap the percentage of a residential lot that can be covered by roofs, driveways, patios, and sidewalks, commonly between 30 and 65 percent of total lot area depending on the zoning district. Smaller lots often face tighter limits. If a new slab would push the property over its cap, you’ll need either a variance or a stormwater management plan showing how you’ll handle the extra runoff. Some jurisdictions let you offset the increase with permeable pavers elsewhere on the lot or a rain garden. This is a separate approval from the building permit and can add weeks.
If your property is in a homeowners’ association, check the CC&Rs separately. HOA rules run independently from municipal codes and can restrict materials, placement, or appearance the city doesn’t care about. Violating them won’t get you a municipal fine, but it can trigger HOA penalties and forced removal.
Call 811 Before You Dig
Before any excavation, federal law requires anyone planning to dig to use their state’s one-call notification system to locate underground utilities.1Office of the Law Revision Counsel. 49 U.S. Code 60114 – One-Call Notification Systems That applies to homeowners on their own property, not just professional contractors. The Pipeline and Hazardous Materials Safety Administration specifically rejected a proposed homeowner exemption, so even hand-tool excavation in your own backyard falls under the requirement.2Federal Register. Pipeline Safety: Pipeline Damage Prevention Programs
The call to 811 is free. Most states require you to call at least two to three business days before digging. Utility companies then send locators to mark buried gas, electrical, water, and telecom lines with color-coded paint or flags. If you skip the call and hit a line, you’re financially responsible for the repair and potentially liable for injuries. If you make the call and a line was mismarked or missed, liability shifts to the utility.
How to Confirm What Your Jurisdiction Requires
Your local building department or planning department is the only reliable source. Start on the website, where most post permit guides, fee schedules, and exemption lists. If the site doesn’t answer your question clearly, call or visit. Have your property address ready so staff can look up your zoning district, setbacks, and any recorded easements on the spot.
Understand that a building permit and a zoning permit are two different things. A building permit confirms your project meets structural and safety codes. A zoning permit confirms it complies with land-use rules like setbacks, lot coverage, and allowed uses. Some jurisdictions combine them into one application; others require separate filings. A slab exempt from a building permit because of its size may still need zoning approval if it sits close to a property line or pushes the lot over its impervious surface cap.
What a Permit Application Involves
When a permit is required, the package usually includes three things. The application form asks for your contact information, property address, and a description of the proposed work. A site plan is the most important supporting document: a scaled drawing showing existing structures, property lines, and the exact location and dimensions of the slab, with distances from the slab to each property line so the reviewer can confirm setback compliance. For a simple patio slab, many departments accept a clean hand-drawn plan as long as it’s to scale and clearly dimensioned. You’ll also provide a project description covering the slab’s intended use, its length, width, and thickness, and its materials. For a slab that will support a structure, the department may ask for the concrete mix design or compressive strength specification and possibly a soil report. Expansive clay soils and flood zones draw more scrutiny and may require engineered drawings.
Permit fees for a simple slab typically run from around $50 to a few hundred dollars, depending on scope and the local fee schedule. Some jurisdictions charge a flat fee for minor residential work; others calculate fees based on the project’s estimated value. Plan review for a straightforward slab on grade might take a few days; more complex projects involving structural foundations or drainage modifications can take several weeks. If the reviewer spots issues, you’ll get a correction letter and have to revise and resubmit.
Once a permit is issued, expect at least one inspection before you pour and one after the slab cures. The pre-pour inspection checks that the subgrade is prepared, forms are set to the correct dimensions, and any required reinforcement or vapor barriers are in place. Pour before the inspector signs off and the department can make you remove and redo the work. The final inspection confirms the finished slab matches the approved plans. Keep the permit posted visibly at the site until final inspection is passed.
Doing the Work Yourself or Hiring It Out
For a basic patio slab, most jurisdictions allow homeowners to pull their own building permit and do the work themselves under an owner-builder permit. You take on the same responsibility a licensed contractor would: the work must meet code, you must schedule inspections, and you’re personally liable if something goes wrong.
Foundation work is different. Many states require that structural foundation work be performed or supervised by a licensed contractor, and some require engineered drawings signed by a licensed professional engineer. If you’re pouring a pad for a garage or ADU, confirm your jurisdiction allows owner-builder work at that scope before you start. Hiring a licensed contractor generally means the contractor pulls the permit, manages inspections, and guarantees code compliance, which costs more upfront but shifts much of the liability. Hiring someone unlicensed to save money usually leaves you responsible for the deficient or unpermitted work and strips away the protection of a licensed contractor’s bond and insurance.
What Happens If You Skip the Permit
Unpermitted work compounds over time. If a building inspector discovers a slab that should have been permitted, the first step is usually a stop-work order. Fines follow. Penalties vary, but daily fines of several hundred dollars are not unusual, and they run until you either obtain a permit or remove the work.
Most jurisdictions offer a retroactive or after-the-fact permit that lets you legalize existing work. The fee is typically double or triple the original, and the department may require you to expose parts of the work for inspection, which can mean cutting into the slab. If the work doesn’t meet code, you’ll have to bring it into compliance before the retroactive permit is approved, sometimes at significant expense.
Unpermitted work also creates insurance risk. If damage traces back to unpermitted construction — a drainage problem that floods your basement, for instance, or a neighbor’s yard — your homeowner’s insurance carrier may deny the claim on the grounds the work wasn’t built to code or properly inspected. You’d be personally liable with no insurer backing you.
The problem becomes most visible when you sell. Unpermitted improvements routinely surface during buyer inspections and title searches. Buyers may demand a price cut, require a retroactive permit before closing, or walk away. A slab that cost a few thousand dollars to pour can create a problem worth many times that at the closing table.