What Size Carport Requires a Permit? Size Exemption Thresholds by State (2025)
The square footage of your carport is one of the key factors determining whether a permit is required. But the threshold varies significantly by state — and even by county within a state. This guide consolidates the most accurate thresholds available for 2025.
Size exemptions apply to detached accessory structures only. If your carport is attached to your home, a permit is required regardless of size — in every U.S. jurisdiction. See our attached vs. detached guide for more.
How Size Exemptions Work
Most U.S. jurisdictions follow the International Residential Code (IRC) as their base building code, with local amendments. The IRC itself does not contain a blanket size exemption for accessory structures — exemptions are established by individual states and counties through amendments to the base code.
This means two things:
- There is no single national rule — you must look at your specific county's adopted code
- Within any given state, city limits often have stricter requirements than unincorporated county areas
The thresholds in the table below represent the most commonly adopted thresholds for unincorporated county areas (outside city limits). If you live inside a city, your city's building code may override the county and impose a stricter threshold or no exemption at all.
Size Exemption Thresholds by State (2025)
| State | Typical Exemption (Detached, Unincorporated) | Notes | State Guide |
|---|---|---|---|
| Alabama | 144 sq ft | Follows IRC 2021 with local amendments | AL Guide |
| Alaska | 200 sq ft | Many rural boroughs have no permitting | AK Guide |
| Arizona | 200 sq ft | Maricopa County strict on HOA areas | AZ Guide |
| Arkansas | Varies (100–200 sq ft) | No statewide residential code; county rules | — |
| California | 120 sq ft (some counties) | Many counties: no exemption; CBC governs | CA Guide |
| Colorado | 120 sq ft | Snow load zones may lower threshold | CO Guide |
| Connecticut | No exemption | All accessory structures require permit | — |
| Delaware | 144 sq ft | Follows IRC with state amendments | — |
| Florida | No exemption | All structures require permit (hurricane code) | FL Guide |
| Georgia | 144 sq ft | Local amendments vary significantly | GA Guide |
| Hawaii | No exemption | All structures require permit | — |
| Idaho | 200 sq ft | Rural counties may be more permissive | — |
| Illinois | 150 sq ft | Cook County stricter; Chicago: no exemption | — |
| Indiana | 144 sq ft | Home rule applies; city limits vary | — |
| Iowa | 200 sq ft | Rural counties often more permissive | — |
| Kansas | 120–200 sq ft | Varies significantly by county | — |
| Kentucky | 200 sq ft | Jefferson County (Louisville) stricter | — |
| Louisiana | 400 sq ft | One of the most permissive states | — |
| Maine | 200 sq ft | Many rural towns have no permitting | — |
| Maryland | 120 sq ft | Prince George's/Montgomery: no exemption | — |
| Massachusetts | No exemption | 780 CMR requires permit for all structures | — |
| Michigan | 200 sq ft | Township rules vary; check local ordinance | MI Guide |
| Minnesota | 200 sq ft | Metro counties typically stricter | — |
| Mississippi | Varies (100–200 sq ft) | No statewide residential code | — |
| Missouri | 120 sq ft | St. Louis / KC counties stricter | — |
| Montana | 200 sq ft | Rural counties often have no permitting | — |
| Nebraska | 200 sq ft | Douglas County (Omaha): check city code | — |
| Nevada | 200 sq ft | Clark County (Las Vegas) often no exemption | NV Guide |
| New Hampshire | 200 sq ft | Follows IRC; many towns have no code | — |
| New Jersey | No exemption | NJUCC requires permits for all structures | — |
| New Mexico | 200 sq ft | Rural counties more permissive | NM Guide |
| New York | 144 sq ft | NYC: permit required for any structure | — |
| North Carolina | 144 sq ft | Coastal counties: often stricter (wind zones) | NC Guide |
| North Dakota | 200 sq ft | Rural counties may waive requirements | — |
| Ohio | 200 sq ft | Franklin/Cuyahoga (Columbus/Cleveland): stricter | OH Guide |
| Oklahoma | Varies (100–200 sq ft) | No statewide residential code | — |
| Oregon | 200 sq ft | Follows ORS 455; city limits often stricter | OR Guide |
| Pennsylvania | Varies by municipality | No statewide threshold; township rules govern | — |
| Rhode Island | No exemption | All accessory structures require permit | — |
| South Carolina | 144 sq ft | Coastal counties: stricter wind-load rules | — |
| South Dakota | 200 sq ft | Rural counties typically permissive | — |
| Tennessee | 144 sq ft | Follows IRC 2018; local amendments apply | TN Guide |
| Texas | Varies (0–400 sq ft) | No statewide code; county/city rules govern | TX Guide |
| Utah | 200 sq ft | Salt Lake / Davis County: often no exemption | — |
| Vermont | 200 sq ft | Many small towns have no permitting | — |
| Virginia | 256 sq ft | USBC allows local amendments; NOVA stricter | VA Guide |
| Washington | 200 sq ft | King/Snohomish/Pierce: often no exemption | WA Guide |
| West Virginia | 144 sq ft | Rural counties often lax on enforcement | — |
| Wisconsin | 196 sq ft | Milwaukee metro: stricter | — |
| Wyoming | 200 sq ft | Many counties have no permit requirement | — |
The Most Common Carport Sizes — Do They Require a Permit?
To make this more concrete, here's how the most commonly ordered carport sizes land against typical state thresholds:
| Standard Size | Square Footage | Permit Status in Most States |
|---|---|---|
| 10×10 shade canopy | 100 sq ft | Often Exempt (if not anchored) |
| 12×20 single car | 240 sq ft | Permit Usually Required |
| 18×20 single car wide | 360 sq ft | Permit Required |
| 20×20 double car | 400 sq ft | Permit Required |
| 20×40 double car wide | 800 sq ft | Permit Required |
| 24×30 RV/boat cover | 720 sq ft | Permit Required |
The practical takeaway: if you're buying any standard-sized metal carport kit — including the most commonly sold 18×21 and 20×20 sizes — a permit is almost certainly required in most U.S. counties.
Why City Limits Change Everything
The table above covers unincorporated county areas. If your property is inside a city or town, the city's building code governs — not the county's. Cities almost universally have stricter requirements than the surrounding county. Examples:
- Houston, TX: Houston has no city-wide building code for single-family residential, but the county and subdivision rules still apply — and all HOA communities in Houston suburbs have their own restrictions
- Phoenix, AZ: City of Phoenix requires a permit for any detached structure over 200 sq ft; Maricopa County unincorporated has the same threshold
- Charlotte, NC: City requires permit for structures over 100 sq ft; Mecklenburg County unincorporated uses 144 sq ft
- Nashville, TN: Metro Nashville requires permit for all structures; surrounding Williamson County uses 144 sq ft
Before starting any project, call your county building department and ask: "What is the permit exemption threshold for a detached accessory structure — specifically a carport — at [your address]?" This single phone call takes 5 minutes and eliminates all uncertainty. Have your property address ready so they can confirm whether you're in city limits or unincorporated county.
Free: Carport Permit Application Checklist
Everything you need to bring to the building department — including the right questions to ask about size thresholds.
Download Free →Frequently Asked Questions
In almost every U.S. jurisdiction, yes. A 20×20 carport is 400 square feet — well above the exemption threshold in all but the most permissive rural areas (Louisiana allows up to 400 sq ft without a permit in some parishes, but this is an outlier). In Texas, Florida, California, and the Southeast, a 20×20 carport requires a permit. Always confirm with your county building department.
Truly temporary structures — canopies with no ground anchoring that can be assembled and disassembled in under an hour — are often exempt from permit requirements in most counties. However, if you install a "temporary" canopy that stays up year-round and has any ground anchors, sandbags, or concrete weights, many building departments will treat it as a permanent structure. The key question building departments ask is: "Is it intended to remain in place indefinitely?" If yes, it's typically permanent regardless of how it was marketed.
Yes. Setback requirements (minimum distances from property lines) apply to all structures in most zoning codes, even structures that are exempt from permit requirements. A structure below the permit threshold still must respect your zone's setback requirements. Some counties have more permissive setbacks for exempt structures, but assuming zero setback requirements because no permit is needed is a common and costly mistake.