For an uncovered patio at ground level, the building code answer is usually no. That is the question most people are asking, so here it is up front, from two cities that publish their exemption lists plainly.
Austin exempts "a sidewalk, driveway, or concrete flatwork that is not located in the public right-of-way" from building permits. Phoenix exempts "platforms, sidewalks and driveways not more than 30 inches above grade and not over any basement or story below," and its own commentary adds that "decks, sport courts and other similar uses with no roof covering shall also be included in this exception."
The complication is that a building permit is only one of three approvals a patio can touch, and the other two are decided by different people. Nothing about being exempt from the first tells you anything about the other two.
Three Questions, Not One
Your city is asking three separate things about a new patio, and they sit in different departments:
- Is it built safely? The building code question. For flatwork at grade, there is almost nothing to review, which is why the exemptions above exist.
- Is it allowed here? The zoning question. Setbacks, lot coverage, how close to a line an accessory feature may sit.
- Where does the water go? The stormwater question. How much of your lot is now hard surface, and what that does to runoff.
Portland shows the split clearly. Its guidance for adding a concrete patio on grade is not "no permit required." It is: contact Planning and Zoning to find out whether a zoning permit is needed. The building department is not the one with the answer.
If the difference between those two permits is unfamiliar, our guide to zoning permits versus building permits covers which is which and why an exemption from one is not an exemption from the other.
The 30-Inch Line
The one number worth memorizing is 30 inches. It appears in the model code and in city exemptions everywhere, and it marks where a walking surface stops being flatwork and starts being a structure.
Phoenix exempts platforms "not more than 30 inches above grade." Portland requires a building permit for a deck more than 30 inches high and requires none below it. The International Residential Code uses the same threshold for its deck exemption.
Below 30 inches there is no meaningful fall hazard and nothing structural to inspect, so the code steps back. Above it, guards, footings and framing come into play. A patio built into a slope can cross that line at one end without anyone noticing, and the measurement is taken at the highest point above grade, not the average.
The Two That Actually Catch People
Setbacks. A permit exemption waives paperwork, not the zoning code. Accessory features have required distances from side and rear lines, and corner lots often have two front setbacks. A patio poured inside a setback or across an easement can be ordered removed, and concrete is the least forgiving material to be wrong about. Our guide to how close to the property line you can build covers how to find yours.
Impervious coverage. This is the one almost nobody expects. Many cities cap how much of a lot may be covered by surfaces that shed water rather than absorb it, counting the roof, driveway, walkways and patio together. Raleigh's ordinance carries impervious surface limitations along with grandfathering for lots recorded before May 2001, which is a good illustration of how these rules attach to the lot rather than the project.
Two things make this trap effective. It is enforced by a stormwater or zoning reviewer rather than a building inspector, so an exempt project may never pass in front of the person who would catch it. And it is cumulative: a patio that would be fine on an empty lot can push a house with a large driveway over the limit.
Do not assume pavers solve it. People reach for pavers believing they count as permeable. Many ordinances count any hard surface toward the limit unless a permeable system has been specifically engineered and approved as a stormwater control measure. If your lot is near its cap, ask the stormwater reviewer directly how your material will be counted before you buy it.
When the Answer Flips to Yes
An uncovered slab at grade is the simple case. Several common additions move the project firmly into permit territory:
- A roof or cover. The clearest flip. Posts, footings and wind or snow loads make it a structure. Phoenix's exemption says so by its own terms: it applies to uses "with no roof covering."
- Attaching to the house. A structure connected to the dwelling brings the connection, and often the foundation, into the review.
- Raising it more than 30 inches at any point.
- A hot tub or spa on the slab, which brings electrical and often a barrier requirement.
- An outdoor kitchen with gas or plumbing, where the trades need permits even if the slab does not.
- Retaining walls to build the pad on a slope. The model code exempts walls up to 4 feet measured from the bottom of the footing, and not if they support a surcharge.
For a covered patio the project is no longer flatwork, and the rules in our patio permit guide apply in full.
What to Do Before You Pour
Four calls or clicks, in this order, and none of them cost anything:
- Ask the building department whether an uncovered patio at grade is on their exempt list. Ask for the list rather than a verbal yes.
- Ask zoning for the setbacks that apply to accessory features on your lot, and whether a zoning permit is required even when a building permit is not.
- Ask about impervious coverage. Use the words "impervious" or "lot coverage" and ask what your limit is and what is already counted against it.
- Check for easements on your plat or deed. Utility easements running along rear lot lines are common, and a slab poured over one can be broken out at your expense when the utility needs access.
The document that answers most of that at once is a site plan: lot lines, setbacks, easements, existing hard surfaces, and the proposed patio dimensioned to all of them. It is what a zoning reviewer wants, it is what shows your coverage math, and it is cheap relative to a poured slab. If you need one, we draw permit-ready site plans from your parcel data.
The Bottom Line
At ground level and uncovered, most cities do not require a building permit for a concrete slab or a paver patio, and two of them say so in exactly those words. That is a real answer, not a hedge.
It is also the least interesting of the three questions. Setbacks and impervious coverage decide more patio projects than the building code does, they are handled by people you have not called yet, and unlike a framing correction, neither is fixable after the concrete cures.