Do I need a permit to add a shed or small outbuilding?
It depends on the specifics
One-story detached sheds are typically exempt up to 200 square feet under the residential code — but the number people quote is 120, and both are right depending on which code your jurisdiction adopted.
What changes the answer
- Under 200 sq ft, one storey, detached, no plumbing — typically exempt under the IRC as adopted since 2015
- Under 120 sq ft — the older IRC ceiling and the current commercial-code ceiling, and still the number many jurisdictions amend back down to
- Over whichever ceiling applies where you are — typically requires a permit
- Running electricity or water to it — that work needs its own permit regardless of the shed's size
- Setback distance from property lines is zoning, and applies even to exempt sheds
These thresholds come from the model code and are commonly amended locally, which is usually where people get caught.
Why it matters
This is the single most contradictory number in residential permitting, and the contradiction is real rather than a matter of someone being wrong. Assuming the more generous figure is exactly how people end up with a structure that has to come down.
Confirm the requirement with the authority that would issue the permit before deciding.
The version of this people actually ask
Is a shed under 200 square feet exempt, or is it 120?
Both numbers are in live use. The IRC has exempted detached accessory structures up to 200 square feet since its 2015 edition, and the IBC has said 120 square feet the whole time — so a jurisdiction on an older IRC, or one that amended toward the commercial figure, is at 120 while its neighbour is at 200. The state adoption is what settles it, and it is worth one phone call rather than a guess, because the difference is a structure you may be ordered to remove.
Do I need a permit for a prefab or resin shed I bought at a store?
The code does not care whether you built it or bought it flat-packed — it measures floor area, storeys, and whether the thing is detached. A 10x12 resin shed is 120 square feet of floor area and is judged exactly as a site-built one of the same size would be. Delivery in a box is not an exemption, and neither is the ability to move it later unless your jurisdiction has a specific rule for temporary structures.
Do I need a permit to put electricity in my shed?
Almost always yes, and separately from the shed. Running a circuit out to an outbuilding is a branch circuit or a feeder depending on how it is done, it is usually buried, and burial depth, conductor sizing and whether the shed needs its own disconnect and grounding electrode are the things inspection exists to catch. An exempt shed with unpermitted power in it is still unpermitted electrical work.
Does a shed on skids or blocks still need a permit?
Foundation type is not what the exemption turns on — floor area is. Some jurisdictions do treat a structure with no permanent foundation more leniently, and some treat anything left in place for more than a set period as permanent regardless of what it sits on. Worth asking directly, because this is one of the places where local practice diverges most from the printed code.
This is the typical rule, not your answer
This is the typical rule in the United States and not a decision about your property — permitting is run by more than 22,000 separate authorities and any of them can amend the code it adopts, so confirm with your local building department before you start. Put a ZIP in to see what applies in that state, and how to reach the office that decides.
IRC R105.2 exempts one-story detached accessory structures not exceeding 200 sq ft in the 2015, 2018 and 2021 editions. Earlier IRC editions and the IBC at 105.2 both say 120 sq ft, which is why the smaller figure is still quoted everywhere and is a common local amendment.
Add a shed or small outbuilding state by state
Which building code a state adopts, and whether it binds the whole state or leaves it to each city, changes how far the rule above gets you. These pages carry that, plus the county building departments we have verified in each.
- Shed permits in Texas Mixed — state and local · 45 verified county offices
- Shed permits in Georgia Statewide adoption · 29 verified county offices
- Shed permits in Virginia Statewide adoption · 29 verified county offices
- Shed permits in North Carolina Statewide adoption · 26 verified county offices
- Shed permits in Illinois Home rule — local adoption · 23 verified county offices
- Shed permits in Michigan Statewide adoption · 22 verified county offices
Other projects
- Build a deckA permit is usually required once a deck is more than 200 square feet, more than 30 inches above grade, serves an exit door, or is attached to the house.
- Put up a fenceFences under 7 feet are typically exempt from a building permit — but height limits, corner-visibility rules and pool-barrier requirements are set locally and catch people constantly.
- Replace a water heaterReplacing a water heater almost always requires a permit, even though it is routinely done without one.
- Remove or open up an interior wallIf the wall is load-bearing, a permit and engineered drawings are required. If you are not certain whether it is load-bearing, assume it is.
- Upgrade or replace an electrical panelPanel and service work always requires a permit, and in most places must be done by a licensed electrician.
- Replace a roofRe-roofing normally requires a permit, and the number of existing layers is what usually decides whether you can go over the top.